Levothyroxine (Lexi-Drugs)

ALERT: US Boxed Warning
  Weight reduction:
Drug Shortages

One or more forms of this drug may be in short supply or unavailable. Refer to the following for additional information:

ASHP: http://www.ashp.org/menu/DrugShortages

Pronunciation

(lee voe thye ROKS een)

Brand Names: US

Euthyrox; Levoxyl; Synthroid; Tirosint; Tirosint-SOL; Unithroid; Unithroid Direct

Brand Names: Canada

Eltroxin; Euthyrox; Soloxine [DSC]; Synthroid

Pharmacologic Category

Thyroid Product

Dosing: Adult

Doses should be adjusted based on clinical response and laboratory parameters.

Hypothyroidism:

Oral:

Adults (healthy) who have been hypothyroid for only a few months: Initial: 1.6 mcg/kg/day; adjust dose by 12.5 to 25 mcg/day every 4 to 6 weeks as needed. Usual doses are ≤200 mcg/day (range: 100 to 125 mcg/day [70 kg adult]); doses ≥300 mcg/day are rare (consider poor compliance, malabsorption, and/or drug interactions).

Adults >50 years of age without evidence of coronary heart disease (off-label): Lower starting doses (eg, 50 mcg/day) may be preferred (ATA/AACE [Garber 2012]).

Adults with cardiac disease: Initial: 12.5 to 25 mcg/day; adjust dose by 12.5 to 25 mcg increments at 6- to 8-week intervals as needed

Adults with severe longstanding hypothyroidism: Initial: 12.5 to 25 mcg/day; adjust dose by 12.5 to 25 mcg/day every 2 to 4 weeks as appropriate

Pregnant patients: Dosage requirements may increase during pregnancy in patients with preexisting disease. If new onset hypothyroidism occurs initiate therapy with 1.6 mcg/kg/day (for severe hypothyroidism) or 1 mcg/kg/day (for mild hypothyroidism [TSH <10 milliunits/L]) followed by appropriate dosage adjustments every 4 weeks.

IM, IV (off-label route [IM] and off-label use): ~75% of the oral dose by IV administration (ATA [Jonklaas 2014]). Note: Bioavailability of the oral formulation is highly variable, but absorption has been measured to be ~80%, when the oral tablet formulation was administered in the recommended fasting state (Dickerson 2010; Fish 1987).

TSH suppression: Oral:

Well-differentiated thyroid cancer (papillary and follicular): Highly individualized; Doses >2 mcg/kg/day may be needed to suppress TSH to <0.1 milliunits/L in high-risk tumors. For intermediate-risk tumors, initial TSH suppression to 0.1 to 0.5 milliunits/L is recommended; for low-risk tumors, TSH may be maintained at or slightly below the lower limit of normal (0.1 to 0.5 milliunits/L [if low serum thyroglobulin levels]) or at 0.5 to 2 milliunits/L [if undetectable serum thyroglobulin levels or post-lobectomy] (ATA [Haugen 2016]).

Benign nodules and nontoxic multinodular goiter: Routine use of T4 for TSH suppression is not recommended in patients with benign thyroid nodules. In patients deemed appropriate candidates, treatment should never be fully suppressive (TSH <0.1 milliunits/L) (AACE/ACE/AME [Gharib 2016]; ATA [Haugen 2016]).

Myxedema coma or stupor (off-label dose) (may use in combination with liothyronine): IV: Initial loading dose: 200 to 400 mcg; followed by a daily replacement dose of 1.2 mcg/kg/day (which is 75% of the 1.6 mcg/kg oral daily replacement dose reduced for IV administration); smaller doses should be considered for smaller or older patients and those with a history of coronary disease or arrhythmia; institute oral therapy after the patient improves clinically (ATA [Jonklaas 2014]).

Cadaveric organ recovery (hormonal resuscitation) (off-label use): IV: Initial: 20 mcg bolus followed by a continuous infusion of 10 mcg/hour administered to the brain-dead donor who is hemodynamically unstable requiring significant vasopressor support; give concomitantly with methylprednisolone, dextrose, and regular insulin (Salim 2007).

Subclinical hypothyroidism (if treated) (off-label use): Oral: Initial: 25 to 75 mcg/day, with higher doses usually required for those presenting with higher TSH values (ATA/AACE [Garber 2012]) or 1.5 mcg/kg/day (for patients without heart disease) or 25 or 50 mcg/day (for patients with cardiac disease) (ETA [Pearce 2013]).

Dosing: Geriatric

Doses should be adjusted based on clinical response and laboratory parameters.

Hypothyroidism: Oral: Initial: 12.5 to 25 mcg/day; adjust dose every 6 to 8 weeks until euthyroid. Elderly patients may only require <1 mcg/kg/day.

Myxedema coma: Refer to adult dosing; lower doses may be needed.

Subclinical hypothyroidism (if treated) (off-label use): Oral: Initial dosing is generally lower than that required in the treatment of overt hypothyroidism; higher serum TSH targets may be appropriate in elderly patients. In elderly patients with TSH <10 milliunits/L, lack of symptoms, or lack of risk factors, observation only is recommended (ATA/AACE [Garber 2012]; Pearce 2013).

Dosing: Renal Impairment: Adult

There are no dosage adjustments provided in the manufacturer’s labeling.

Dosing: Hepatic Impairment: Adult

There are no dosage adjustments provided in the manufacturer’s labeling.

Dosing: Adjustment for Toxicity: Adult

Cardiac symptoms (onset or worsening): Manufacturer labeling recommends reducing dosage or withholding therapy for 7 days and then resuming therapy at reduced dosage. Specific dosing recommendations are not provided.

Dosing: Pediatric

Note: Doses should be adjusted based on clinical response and laboratory parameters; on a weight basis, dosing is higher in infants and children than adults due to the higher metabolic clearance.

Hypothyroidism (acquired or congenital): Note: Hyperactivity in older children may be minimized by starting at one-quarter (25%) of the recommended dose and increasing each week by that amount until the full dose is achieved (4 weeks).

Oral:

1 to 3 months: 10 to 15 mcg/kg/dose once daily; in severe cases of hypothyroidism (serum T4 <5 mcg/dL), initiating at higher doses (12 to 17 mcg/kg/dose) may be necessary (AAP 2006; ATA [Jonklaas 2014]; Léger 2014; Selva 2002).

>3 to 6 months: 8 to 10 mcg/kg/dose once daily

>6 to 12 months: 6 to 8 mcg/kg/dose once daily

1 to 5 years: 5 to 6 mcg/kg/dose once daily

6 to 12 years: 4 to 5 mcg/kg/dose once daily

>12 years with incomplete growth and puberty: 2 to 3 mcg/kg/dose once daily

Adolescents with growth and puberty complete: 1.6 mcg/kg/dose once daily; adjust dose by 12.5 to 25 mcg/day every 4 to 6 weeks as needed. Usual doses are ≤200 mcg/day (range: 100 to 125 mcg/day [70 kg adult]); doses ≥300 mcg/day are rare (consider poor compliance, malabsorption, and/or drug interactions).

Cardiac disease: Note: Lower initial doses are recommended.

Infants and Children: Initial: ~50% of target replacement dose; increase after 2 weeks based on free thyroxine levels (Léger 2014)

Adolescents with growth and puberty complete: Initial: 12.5 to 25 mcg/day; adjust dose by 12.5 to 25 mcg increments at 6- to 8-week intervals as needed

IV: Note: The relative bioavailability of injectable and oral levothyroxine has not been established; use caution when switching patients from oral to IV as accurate dosing conversions have not been established. Infants, Children, and Adolescents: ~75% to 80% of the oral dose has been suggested by guidelines (ATA [Jonklaas 2014]; Léger 2014).

Thyroid-stimulating hormone (TSH) suppression in well differentiated thyroid cancer (papillary): Infants, Children, and Adolescents: Oral: Highly individualized; doses >2 mcg/kg/day may be needed to suppress TSH to <0.1 milliunits/L in high-risk tumors; for intermediate-risk tumors, initial TSH suppression to 0.1 to 0.5 milliunits/L is recommended; for low-risk tumors, TSH may be maintained at 0.5 to 1 milliunits/L (ATA [Francis 2015]).

Organ donor management in brain-dead patients (hormone replacement therapy) (Nakagawa 2008; Zuppa 2004): IV:

Infants <6 months: Initial: 5 mcg/kg bolus dose, followed by 1.4 mcg/kg/hour infusion

Infants 6 to 12 months: Initial: 4 mcg/kg bolus dose, followed by 1.3 mcg/kg/hour infusion

Children 1 to 5 years: Initial: 3 mcg/kg bolus dose, followed by 1.2 mcg/kg/hour infusion

Children 6 to 12 years: Initial: 2.5 mcg/kg bolus dose, followed by 1 mcg/kg/hour infusion

Children ≥12 years and Adolescents ≤16 years: Initial: 1.5 mcg/kg bolus dose, followed by 0.8 mcg/kg/hour infusion

Adolescents >16 years: Initial: 0.8 mcg/kg bolus dose, followed by 0.8 mcg/kg/hour infusion

Dosing: Renal Impairment: Pediatric

There are no dosage adjustments provided in the manufacturer’s labeling.

Dosing: Hepatic Impairment: Pediatric

There are no dosage adjustments provided in the manufacturer’s labeling.

Use: Labeled Indications

Oral:

Hypothyroidism: Replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology. Specific indications include primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism. Note: Levothyroxine monotherapy is recommended as the preferred thyroid preparation for the treatment of hypothyroidism (ATA [Jonklaas 2014]; ES [Fleseriu 2016]).

Pituitary thyrotropin-stimulating hormone suppression: An adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.

Injectable: Treatment of myxedema coma

Use: Off-Label: Adult

  Cadaveric organ recovery (hormonal resuscitation)Level of Evidence [C]

Data from a retrospective review of brain-dead donors who successfully donated organs supports the use of intravenous levothyroxine given concomitantly with an ampule of 50% dextrose, methylprednisolone sodium succinate, and regular insulin (goal blood glucose: 120 to 180 mg/dL) in hemodynamically unstable brain-dead donors who require significant vasopressor support to increase the quantity and quality of organs available for transplantation Ref. Early use of levothyroxine therapy (with aggressive blood product resuscitation) may significantly increase the number of solid organs donated per donor Ref. Additional data may be necessary to further define the role of levothyroxine in this setting. Another protocol using liothyronine (T3) has been used with success and is recommended over the use of levothyroxine Ref.

  Subclinical hypothyroidismLevel of Evidence [G]

The American Association of Clinical Endocrinologists/American Thyroid Association Clinical Practice Guidelines for Hypothyroidism in Adults and the European Thyroid Association Guideline for Management of Subclinical Hypothyroidism recommend thyroid replacement with levothyroxine in select patients with subclinical hypothyroidism (persistently elevated TSH with free T4 within normal range). In non-elderly patients (<65 to 70 years of age), treatment is recommended if TSH ≥10 milliunits/L (regardless of symptoms) and may also be considered in symptomatic patients with mild to moderate TSH elevation (4 to 10 milliunits/L). In elderly patients (>70 years of age), consider treatment if TSH ≥10 milliunits/L and clear symptoms of hypothyroidism present, or if high vascular risk factors present. In elderly patients with TSH <10 milliunits/L, lack of symptoms, or lack of risk factors, observation only is recommended Ref.

Level of Evidence Definitions
  Level of Evidence Scale
Clinical Practice Guidelines

Hypothyroidism:

ATA/AACE, “Clinical Practice Guidelines for Hypothyroidism in Adults: Cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association.” 2012

American Thyroid Association Task Force on Thyroid Hormone Replacement, “Guidelines for the Treatment of Hypothyroidism.” 2014

European Thyroid Association, “2013 ETA Guideline: Management of Subclinical Hypothyroidism.” 2013

Hypopituitarism:

Endocrine Society, “Hormonal Replacement in Hypopituitarism in Adults,” 2016

Thyroid Nodules and Differentiated Thyroid Cancer:

AACE/AAES Medical/Surgical Guidelines for Clinical Practice: Management of Thyroid Carcinoma, May/June 2001

AACE/ACE/AME Guidelines for Clinical Practice for the Diagnosis and Management of Thyroid Nodules-2016 Update

American Thyroid Association (ATA), “Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer,” 2016

National Comprehensive Cancer Network® (NCCN), Clinical Practice Guidelines in Oncology™, Thyroid

Administration: IM

May be administered intramuscularly when oral administration is not feasible (off-label route)

Administration: IV

May be administered by IV injection.

Cadaveric organ recovery (hormonal resuscitation) (off-label use): After IV bolus administration, may administer as a continuous infusion (Salim 2007).

Administration: Oral

Administer consistently in the morning on an empty stomach, at least 30 to 60 minutes before food. Alternatively, may consistently administer at night 3 to 4 hours after the last meal (AACE/ATA [Garber 2012]; ATA [Jonklaas 2014]). Do not administer within 4 hours of calcium- or iron-containing products or bile acid sequestrants.

Capsule: Must be swallowed whole; do not cut, crush, or chew.

Solution (Tirosint): May administer undiluted or diluted in water only (do not dilute with any other liquid); if administering undiluted, squeeze contents of single unit-dose ampule into mouth or onto a spoon and administer immediately. If diluting with water, squeeze contents of ampule into a glass or cup, stir, and then administer entire contents immediately. Rinse glass or cup with additional water and administer contents to ensure entire dose is consumed.

Tablet: Administer with a full glass of water (choking, gagging, and dysphagia have been reported with some formulations). May be crushed and suspended in 5 to 10 mL of water; suspension should be used immediately.

Administration: Other

Nasogastric tube: Bioavailability of levothyroxine (crushed tablets suspended in water) is reduced if administered with enteral tube feeds. Since holding feedings for at least 1 hour before and after levothyroxine administration may not completely resolve the interaction, an increase in dose (eg, additional 25 mcg) may be necessary (Dickerson 2010). Tirosint oral solution product labeling does not provide recommendations regarding nasogastric administration.

Administration: Pediatric

Oral: Administer consistently on an empty stomach 30 to 60 minutes prior to breakfast. Alternatively, may consistently administer at night 3 to 4 hours after the last meal (ATA [Jonklaas 2014]). If administration on an empty stomach poses a challenge, particularly in infants and small children, it may be administered with food to improve adherence and consistency of administration (Zeitler 2010). Do not administer within 4 hours of other medications known to interfere with levothyroxine absorption (eg, calcium- or iron-containing products or bile acid sequestrants).

Capsules: Children ≥6 years and Adolescents: Must be swallowed whole; do not cut, crush, or attempt to dissolve capsules in water to prepare a suspension.

Solution (Tirosint-SOL): May administer undiluted or diluted in water only (do not dilute with any other liquid).

Undiluted: Squeeze contents of single unit-dose ampule into mouth or onto a spoon and administer immediately.

Dilution with water: Squeeze contents of ampule into a glass or cup containing water, stir, and then administer entire contents immediately. Rinse glass or cup with additional water and administer contents to ensure entire dose is consumed.

Tablets: Administer with a full glass of water (choking, gagging, and dysphagia has been reported with some formulations). For infants and children who cannot swallow tablet whole, crush tablet and mix with small amount (5 to 10 mL) of water, breast milk, or non-soy-based formula and use immediately (AAP 2006; ATA [Jonklaas 2014]; Léger 2014).

Nasogastric tube: Bioavailability of levothyroxine (crushed tablets suspended in water) is reduced if administered with enteral tube feeds. Since holding feedings may not be appropriate for some patients and holding feedings for at least 1 hour before and after levothyroxine administration may not completely resolve the interaction, an increase in dose (eg, additional 25 mcg in adults) may be necessary (Dickerson 2010).

Parenteral:

IV: Administer IV over 2 to 3 minutes; for organ donor management in brain-dead patients, the IV bolus is followed by continuous IV infusion (Nakagawa 2008; Zuppa 2004)

IM: May be administered intramuscularly when oral administration is not feasible (Levothyroxine injection Canadian product labeling 2017)

Storage/Stability

Capsules and tablets: Store at 25°C (77°F); excursions are permitted between 15°C and 30°C (59°F and 86°F). Protect from heat, light, and moisture.

Oral solution (Tirosint): Store in original container (closed aluminum pouch) at 25°C (77°F); excursions are permitted between 15°C and 30°C (59°F and 86°F). Keep ampules in pouch until ready to use; after opening the pouch, all ampules in the pouch should be used within 15 days.

Injection: Store at 20°C to 25°C (68°F to 77°F). Protect from light.

Additional stability data:

Stability in polypropylene syringes (100 mcg/mL in NS) at 5°C ± 1°C is 7 days (Gupta 2000).

Stability in latex-free, PVC minibags protected from light and stored at 15°C to 30°C (59°F to 86°F) was 12 hours for a 2 mcg/mL concentration or 18 hours for a 0.4 mcg/mL concentration in NS. May be exposed to light; however, stability time is significantly reduced, especially for the 2 mcg/mL concentration (Strong 2010).

Preparation for Administration: Adult

Dilute vial for injection with 5 mL normal saline. Reconstituted concentrations for the 100 mcg, 200 mcg, and 500 mcg vials are 20 mcg/mL, 40 mcg/mL, and 100 mcg/mL, respectively. Shake well and use immediately after reconstitution (manufacturer labeling suggests reconstituted vial is stable for 4 hours); discard any unused portions.

Preparation for Administration: Pediatric

Parenteral: Reconstitute vial for injection with 5 mL NS. Final concentration is dependent upon vial size; concentrations for the 100 mcg, 200 mcg, and 500 mcg vials are 20 mcg/mL, 40 mcg/mL, and 100 mcg/mL, respectively. Shake well and use immediately after reconstitution (manufacturer labeling suggests reconstituted vial is stable for 4 hours); discard any unused portions.

Compatibility

See Trissel’s IV Compatibility Database

Extemporaneously Prepared

Note: A levothyroxine oral solution (multiple concentrations) is commercially available (Tirosint-SOL).

25 mcg/mL Oral Suspension

A 25 mcg/mL oral suspension may be made with tablets and 40 mL glycerol. Crush twenty-five 100 mcg levothyroxine tablets in a mortar and reduce to a fine powder. Add small portions of glycerol and mix to a uniform suspension. Transfer to a calibrated 100 mL amber bottle; rinse the mortar with about 10 mL of glycerol and pour into the bottle; repeat until all 40 mL of glycerol is used. Add quantity of water sufficient to make 100 mL. Label “shake well” and “refrigerate”. Stable for 8 days refrigerated.

Boulton DW, Fawcett JP, and Woods DJ, “Stability of an Extemporaneously Compounded Levothyroxine Sodium Oral Liquid,” Am J Health Syst Pharm, 1996, 53(10):1157-61.[PubMed 8734676]

Medication Patient Education with HCAHPS Considerations

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience hair loss. Have patient report immediately to prescriber angina, tachycardia, abnormal heartbeat, headache, dizziness, passing out, vision changes, shortness of breath, loss of strength and energy, lack of appetite, increased appetite, excessive weight gain or loss, swelling of arms or legs, diarrhea, abdominal cramps, vomiting, irritability, anxiety, emotional instability, tremors, insomnia, temperature sensitivity, sweating a lot, leg cramps, muscle weakness, flushing, bone pain, or menstrual irregularities (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer:Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

Medication Safety Issues
  Sound-alike/look-alike issues:
  Administration issues:
  Other safety concerns:
Contraindications

Injection: There are no contraindications listed in the manufacturer’s labeling when used for labeled indication (treatment of myxedema coma); consider contraindications for oral therapy if using as a temporary substitute for oral treatment (off-label use) in patients with chronic hypothyroidism.

Oral: Uncorrected adrenal insufficiency; hypersensitivity to glycerol (Tirosint oral solution); Note: Product labels may vary; also consult product labels. Reported hypersensitivity to levothyroxine or any component of the formulation is not considered an absolute contraindication (ATA [Jonklaas 2014]); refer to Warnings/Precautions.

Canadian labeling: Additional contraindications (not in US labeling): Untreated subclinical thyrotoxicosis, overt thyrotoxicosis of any etiology, acute MI, acute myocarditis, or acute pancarditis.

Warnings/Precautions

Disease-related concerns:

• Adrenal insufficiency: Use with caution in patients with adrenal insufficiency; symptoms may be exaggerated or aggravated. Treatment with glucocorticoids should precede levothyroxine therapy in patients with adrenal insufficiency. Use is contraindicated in patients with uncorrected adrenal insufficiency.

• Benign thyroid nodules: Appropriate use: Routine use of T4 for thyroid stimulating hormone (TSH) suppression is not recommended in patients with benign thyroid nodules. Treatment should never be fully suppressive (TSH <0.1 milliunits/L) (AACE/ACE/AME [Gharib 2016]; ATA [Haugen 2016]).

– Use of T4 may be considered in association with iodine supplementation only in young patients residing in iodine-deficient areas with small thyroid nodules and no evidence of functional autonomy (AACE/ACE/AME [Gharib 2016]).

– Use should be avoided in postmenopausal women, elderly patients, patients with cardiovascular disease, osteoporosis, large thyroid nodules or long-standing goiters, or low-normal TSH levels (AACE/ACE/AME [Gharib 2016]).

• Cardiovascular disease: Use with caution and reduce dosage in patients with cardiovascular disease; patients with developing or worsening cardiac symptoms should have their dose reduced or therapy withheld for 7 days and then resumed at a reduced dose. Chronic hypothyroidism predisposes patients to coronary artery disease; monitor patients closely for development of cardiac ischemia. Similarly, patients with heart failure and hypothyroidism should be closely followed.

• Diabetes: Use with caution in patients with diabetes mellitus (may worsen glycemic control) and diabetes insipidus (thyroid hormone increases glomerular filtration rate and downregulates aquaporin channels in the renal tubules, which could affect urinary output) (Mariani 2012).

• Osteoporosis: Long-term therapy can decrease bone mineral density and appears to be dose-related (Schneider 1994). Postmenopausal women and women using suppressive doses should receive the lowest dose necessary for clinical response.

• Subacute thyroiditis: Transient and mild hypothyroidism during the recovery phase of subacute thyroiditis often can be managed without treatment; levothyroxine therapy may be required in patients with overt and clinical hypothyroidism (Farwell 2013).

Concurrent drug therapy issues:

• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

Special populations:

• Elderly: Use with caution; suppressed TSH levels may increase risk of atrial fibrillation and mortality secondary to cardiovascular disease (Gharib 2016; Parle 2001). Increase dose slowly and monitor for signs/symptoms of angina.

Dosage form specific issues:

• Product interchangeability: Switching between different levothyroxine products may result in variations in the administered dose and altered TSH values and is not generally recommended; if formulations are changed, close monitoring of TSH is recommended (ATA [Jonklaas 2014]). Pediatric patients with congenital hypothyroidism may be more sensitive to changes in formulation (Carswell 2013).

Other warnings/precautions:

• Hypersensitivity: Patients with reported hypersensitivity to levothyroxine may be managed with dose reductions and slow titration, by switching formulations or products, or referral to an allergist (ATA [Jonklaas 2014]).

• Weight reduction (off-label use): [US Boxed Warning]: Thyroid supplements are ineffective and potentially toxic when used for the treatment of obesity or for weight reduction, especially in euthyroid patients. High doses may produce serious or even life-threatening toxic effects, particularly when used with some anorectic drugs (eg, sympathomimetic amines). Levothyroxine, either alone or with other concomitant therapeutic agents, should not be used for the treatment of obesity or for weight loss.

Geriatric Considerations

Elderly do not have a change in serum thyroxine associated with aging; however, plasma T3 concentrations are decreased 25% to 40% in the elderly. There is not a compensatory rise in thyrotropin suggesting that lower T3 is not reacted upon as a deficiency by the pituitary. This indicates a slightly lower than normal starting dosage of thyroid hormone replacement is usually sufficient in elderly patients than in younger adult patients with subsequent dose increases based on TSH levels. TSH must be monitored since insufficient thyroid replacement (elevated TSH) is a risk for coronary artery disease and excessive replacement (low TSH) may cause signs of hyperthyroidism and excessive bone loss. Some clinicians suggest levothyroxine is the drug of choice for replacement therapy. The once-daily dosing of levothyroxine makes it an ideal choice than other thyroid preparations which may require more frequent dosing and offer no additional benefits over levothyroxine.

Warnings: Additional Pediatric Considerations

Overtreatment may result in craniosynostosis in infants and premature closure of epiphyses in children; monitor use closely. In neonates and infants, cardiac overload, arrhythmias, and aspiration from avid suckling may occur during initiation of therapy (eg, first 2 weeks); monitor closely.

Pregnancy Considerations

Endogenous thyroid hormones minimally cross the placenta; the fetal thyroid becomes active around the end of the first trimester. Levothyroxine has not been shown to increase the risk of congenital abnormalities.

Uncontrolled maternal hypothyroidism may result in adverse neonatal outcomes (eg, premature birth, low birth weight, and respiratory distress) and adverse maternal outcomes (eg, spontaneous abortion, pre-eclampsia, stillbirth, and premature delivery). To prevent adverse events, normal maternal thyroid function should be maintained prior to conception and throughout pregnancy. Thyroid function should be monitored every 4 weeks during the first half of pregnancy, at least once between weeks 26 and 32, and ~6 weeks postpartum. Levothyroxine is considered the treatment of choice for the control of hypothyroidism during pregnancy. Due to alterations of endogenous maternal thyroid hormones, the levothyroxine dose may need to be increased during pregnancy and the dose usually needs to be decreased after delivery (Stagnaro-Green 2011).

Breast-Feeding Considerations

Endogenous thyroid hormones are minimally found in breast milk. The manufacturer recommends that caution be used if administered to a nursing woman.

The amount of endogenous thyroxine found in breast milk does not influence infant plasma thyroid values (van Wassenaer 2002). Levothyroxine was not found to cause adverse events to the infant or mother during breastfeeding (Ito 1993). Adequate thyroid hormone concentrations are required to maintain normal lactation. Appropriate levothyroxine doses should be continued during breastfeeding.

Lexicomp Pregnancy & Lactation, In-Depth
Briggs’ Drugs in Pregnancy & Lactation
Adverse Reactions

Adverse reactions are primarily those of hyperthyroidism due to therapeutic overdosage.

Frequency not defined:

Cardiovascular: Angina pectoris, cardiac arrhythmia, cardiac failure, flushing, increased blood pressure, increased pulse, myocardial infarction, palpitations, tachycardia

Central nervous system: Anxiety, emotional lability, fatigue, headache, heat intolerance, hyperactivity, insomnia, irritability, myasthenia, nervousness, pseudotumor cerebri (children)

Dermatologic: Alopecia, diaphoresis, skin rash

Endocrine & metabolic: Goiter (exophthalmic; IV), menstrual disease, weight loss

Gastrointestinal: Abdominal cramps, diarrhea, increased appetite, vomiting

Genitourinary: Reduced fertility

Hepatic: Increased liver enzymes

Neuromuscular & skeletal: Decreased bone mineral density, muscle spasm, slipped capital femoral epiphysis (children), tremor

Respiratory: Dyspnea

Miscellaneous: Fever

<1%, postmarketing, and/or case reports: Dysgeusia (Syed 2016), seizure

Allergy and Idiosyncratic Reactions
Toxicology
Metabolism/Transport Effects

None known.

Drug Interactions 

Aluminum Hydroxide: May decrease the serum concentration of Levothyroxine. Management: Separate administration of oral levothyroxine and aluminum hydroxide by at least 4 hours.Risk D: Consider therapy modification

Amezinium: Thyroid Products may enhance the stimulatory effect of Amezinium. Risk C: Monitor therapy

Amiodarone: May diminish the therapeutic effect of Thyroid Products. Risk C: Monitor therapy

Apalutamide: May diminish the therapeutic effect of Thyroid Products. Risk C: Monitor therapy

Bile Acid Sequestrants: May decrease the serum concentration of Thyroid Products. Management: Administer oral thyroid products at least 4 h prior to colesevelam, and at least 1 h before or 4-6 h after cholestyramine. Specific recommendations for colestipol are not available. Monitor for decreased concentrations/effects of the thyroid product. Risk D: Consider therapy modification

Calcium Polystyrene Sulfonate: May decrease the serum concentration of Thyroid Products. Management: To minimize risk of interaction, separate dosing of oral calcium polystyrene sulfonate and thyroid products (eg, levothyroxine) or administer calcium polystyrene sulfonate rectally. Monitor for signs/symptoms of hypothyroidism with concomitant use (oral).Risk D: Consider therapy modification

Calcium Salts: May diminish the therapeutic effect of Thyroid Products. Management: Separate the doses of the thyroid product and the oral calcium supplement by at least 4 hours.Risk D: Consider therapy modification

CarBAMazepine: May decrease the serum concentration of Thyroid Products. Risk C: Monitor therapy

Ciprofloxacin (Systemic): May decrease the serum concentration of Thyroid Products. Risk C: Monitor therapy

Estrogen Derivatives: May diminish the therapeutic effect of Thyroid Products. Risk C: Monitor therapy

Fosphenytoin: May decrease the serum concentration of Thyroid Products. Phenytoin may also displace thyroid hormones from protein binding sites. Risk C: Monitor therapy

Iron Salts: May decrease the serum concentration of Levothyroxine. Management: Separate oral administration of iron salts and levothyroxine by at least 4 hours. Separation of doses is not required with parenterally administered iron salts or levothyroxine. Exceptions: Ferric Carboxymaltose; Ferric Gluconate; Ferric Hydroxide Polymaltose Complex; Ferric Pyrophosphate Citrate; Ferumoxytol; Iron Dextran Complex; Iron Isomaltoside; Iron Sucrose. Risk D: Consider therapy modification

Lanthanum: May decrease the serum concentration of Thyroid Products. Management: Administer oral thyroid products at least two hours before or after lanthanum. Risk D: Consider therapy modification

Magnesium Salts: May decrease the serum concentration of Levothyroxine. Management: Separate administration of oral levothyroxine and oral magnesium salts by at least 4 hours.Risk D: Consider therapy modification

Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease the serum concentration of Levothyroxine. Management: Separate oral administration of iron-containing multivitamins and levothyroxine by at least 4 hours. Risk D: Consider therapy modification

Orlistat: May decrease the serum concentration of Levothyroxine. Management: Separate administration of oral levothyroxine and orlistat by a least 4 hours. Monitor patients closely for signs and symptoms of hypothyroidism. Risk D: Consider therapy modification

Patiromer: May decrease the serum concentration of Levothyroxine. Management: Administer oral levothyroxine at least 3 hours before or 3 hours after patiromer. Risk D: Consider therapy modification

Phenytoin: May decrease the serum concentration of Thyroid Products. Phenytoin may also displace thyroid hormones from protein binding sites. Risk C: Monitor therapy

Piracetam: May enhance the adverse/toxic effect of Thyroid Products. Specifically, symptoms including confusion, irritability, and sleep disorder have been described during concomitant use. Risk C: Monitor therapy

Polaprezinc: May decrease the serum concentration of Levothyroxine. Risk D: Consider therapy modification

Raloxifene: May decrease the absorption of Levothyroxine. Risk D: Consider therapy modification

RifAMPin: May decrease the serum concentration of Thyroid Products. Risk C: Monitor therapy

Ritonavir: May diminish the therapeutic effect of Thyroid Products. Risk C: Monitor therapy

Selective Serotonin Reuptake Inhibitors: May diminish the therapeutic effect of Thyroid Products. Thyroid product dose requirements may be increased. Risk C: Monitor therapy

Sevelamer: May decrease the serum concentration of Levothyroxine. Management: Consider separating administration of sevelamer and levothyroxine by at least several hours whenever possible in order to decrease the risk of a significant interaction. Risk D: Consider therapy modification

Sodium Iodide I131: Thyroid Products may diminish the therapeutic effect of Sodium Iodide I131. Risk X: Avoid combination

Sodium Polystyrene Sulfonate: May decrease the serum concentration of Thyroid Products. Management: To minimize risk of interaction, separate dosing of oral sodium polystyrene sulfonate and thyroid products (e.g., levothyroxine) or administer sodium polystyrene sulfonate rectally. Monitor for signs/symptoms of hypothyroidism with concomitant use (oral).Risk D: Consider therapy modification

Somatropin: May diminish the therapeutic effect of Thyroid Products. Risk C: Monitor therapy

Sucralfate: May decrease the serum concentration of Levothyroxine. Risk C: Monitor therapy

Sucroferric Oxyhydroxide: May decrease the serum concentration of Levothyroxine. Management: Administer oral/enteral levothyroxine at least 4 hours before administration of sucroferric oxyhydroxide. No interaction is anticipated with parenteral levothyroxine administration. Risk D: Consider therapy modification

Theophylline Derivatives: Thyroid Products may increase the metabolism of Theophylline Derivatives. Exceptions: Dyphylline. Risk C: Monitor therapy

Tricyclic Antidepressants: Thyroid Products may enhance the arrhythmogenic effect of Tricyclic Antidepressants. Thyroid Products may enhance the stimulatory effect of Tricyclic Antidepressants. Risk C: Monitor therapy

Vitamin K Antagonists (eg, warfarin): Thyroid Products may enhance the anticoagulant effect of Vitamin K Antagonists. Risk C: Monitor therapy

Food Interactions

Taking levothyroxine with enteral nutrition may cause reduced bioavailability and may lower serum thyroxine levels leading to signs or symptoms of hypothyroidism. Soybean flour (infant formula), soy, grapefruit juice, espresso coffee, cottonseed meal, walnuts, calcium, iron, and dietary fiber may interfere with absorption of levothyroxine from the GI tract. Management: Take in the morning on an empty stomach at least 30 minutes before food. Alternatively, may consistently administer at night 3 to 4 hours after the last meal (AACE/ATA [Garber 2012]; ATA [Jonklaas 2014]). Consider an increase in dose if taken with enteral tube feed. Do not administer within 4 hours of calcium- or iron-containing products.

Test Interactions

T4-binding globulin (TBG): Factors that alter binding in serum (ATA/AACE [Garber 2012]):

Note: T4 is ~99.97% protein bound. Factors that alter protein binding will affect serum total T4 levels; however, measurement of serum free T4 (the metabolically active moiety) has largely replaced serum total T4 for thyroid status assessment.

Conditions/states that increase TBG binding: Pregnancy, hepatitis, porphyria, neonatal state

Medications that increase TBG binding: Estrogens, 5-fluorouracil, heroin, methadone, mitotane, perphenazine, selective estrogen receptor modulators (eg, tamoxifen, raloxifene)

Conditions/states that decrease TBG binding: Hepatic failure, nephrosis, severe illness.

Medications that decrease TBG binding: Androgens, anabolic steroids, glucocorticoids, L-asparaginase, nicotinic acid

Thyroxine (T4) and triiodothyronine (T3): Serum binding inhibitors (ATA/AACE [Garber 2012]):

Medications that inhibit T4 and T3 binding: Carbamazepine, furosemide, free fatty acids, heparin, NSAIDS (variable, transient), phenytoin, salicylates

Thyroid gland hormone: Interference with production and secretion (ATA/AACE [Garber 2012]):

Medications affecting iodine uptake: Amiodarone, iodinated contrast agents, iodine, ethionamide

Medications affecting hormone production: Amiodarone, ethionamide, iodinated contrast agents, iodine, sulfonylureas, sulfonamides, thionamides (carbimazole, methimazole, propylthiouracil),

Medications affecting secretion: Amiodarone, iodinated contrast agents, iodine, lithium

Medications inducing thyroiditis: Alemtuzumab, amiodarone, antiangiogenic agents (lenalidomide, thalidomide), denileukin diftitox, interferon alpha, interleukins, lithium, tyrosine kinase inhibitors (sunitinib, sorafenib)

Medications potentially causing the development of Graves’: Alemtuzumab, interferon alpha, antiretroviral therapy

Medications potentially ameliorating thyroiditis (if autoimmune) or Graves’: Glucocorticoids

Hypothalamic-pituitary axis and TSH: Interference with secretion (ATA/AACE [Garber 2012]):

Medications decreasing TSH secretion: Bexarotene, dopamine, dopaminergic agonists (bromocriptine, cabergoline), glucocorticoids, interleukin-6, metformin, opiates, somatostatin analogues (octreotide, lanreotide), thyroid hormone analogues

Medications increasing TSH secretion: Amphetamine, interleukin 2, metoclopramide, ritonavir, St John’s wort

Medications potentially causing hypophysitis: Ipilimumab

Monitoring Parameters

Infants: Monitor closely for cardiac overload, arrhythmias, and aspiration from avid suckling

Infants/children: Monitor closely for under/overtreatment. Undertreatment may decrease intellectual development and linear growth, and lead to poor school performance due to impaired concentration and slowed mentation. Overtreatment may adversely affect brain maturation, accelerate bone age (leading to premature closure of the epiphyses and reduced adult height); craniosynostosis has been reported in infants. Treated children may experience a period of catch-up growth. Monitor TSH and total or free T4 at 2 and 4 weeks after starting treatment; every 1 to 2 months for first year of life; every 2 to 3 months during years 1 to 3; every 3 to 12 months until growth completed. Perform routine clinical examinations at regular intervals (to assess mental and physical growth and development).

Adults: TSH 4 to 6 weeks after treatment initiation or dose changes, 4 to 6 months after adequate replacement dose determined, followed by every 12 months thereafter (or more frequently depending on clinical situation) (ATA [Jonklaas 2014]); T4; heart rate, blood pressure, clinical signs of hypo- and hyperthyroidism; TSH is the most reliable guide for evaluating adequacy of thyroid replacement dosage in primary thyroid dysfunction. TSH may be elevated during the first few months of thyroid replacement despite patients being clinically euthyroid. In cases where T4 remains low and TSH is within normal limits, an evaluation of “free” (unbound) T4 is needed to evaluate further increase in dosage. Free T4(not TSH) should be monitored to guide treatment in patients with central hypothyroidism (ATA/AACE [Garber 2012]; ES [Fleseriu 2016]).

Bone mineral density (particularly with long term use in postmenopausal women)

Reference Range

T4 (thyroxine) serum concentrations: Adults: ~4 to 12 mcg/dL (SI: 51 to 154 nmol/L). Note: Normal range in pregnancy: ~5.5 to 16 mcg/dL (SI: ~71 to 206 nmol/L)

T4 free (free thyroxine; free T4) serum concentrations: Adults: 0.7 to 1.8 ng/dL (SI: 9 to 23 pmol/L). A target range in the mid to upper half of the reference range has been suggested in patients with central hypothyroidism (ES [Fleseriu 2016]).

T3 total (triiodothyronine; total T3) serum concentrations: Adults: 80 to 230 ng/dL (SI: 1.2 to 3.5 nmol/L)

Thyroid-stimulating hormone (TSH) serum concentrations: Adults: Varies by laboratory and assay used; refer to laboratory provided reference range. If an upper and lower limit of normal for a third generation TSH assay is not available, a reference range of 0.45 to 4.12 milliunits/L should be considered (ATA/AACE [Garber 2012]). A higher target range of 4 to 6 milliunits/L has been suggested in patients >70 years of age (ATA [Jonklaas 2014]).

Subclinical hypothyroidism (elevated TSH; free T4 within normal range):

Severe (TSH ≥10 milliunits/L): These patients are at increased risk for heart failure and cardiovascular mortality and should be considered for treatment with L-thyroxine (ATA/AACE [Garber 2012]; ETA [Pearce 2013])

Mild to moderate (TSH 4 to 10 milliunits/L): Decision for when to treat should be tailored to individual patient based on age, symptoms, and cardiovascular risk (ATA/AACE [Garber 2012]; ETA [Pearce 2013])

Advanced Practitioners Physical Assessment/Monitoring

Obtain renal function tests, T3, T4, TSH, and unbound T4 levels; monitor periodically and with dose changes. Monitor periodically and with dose changes. Monitor for hyper/hypothyroidism and adrenal insufficiency. Check blood pressure and heart rate; monitor for worsening cardiovascular disease. Caution patients with diabetes to monitor glucose levels closely (may increase need for oral hypoglycemics or insulin). Obtain bone mineral density in patients on long-term use with post-menopausal women. Assess infants closely for cardiac overload, arrhythmias, or aspiration. Assess pediatric patients closely for over/undertreatment and obtain TSH and total or free T4 at 2 and 4 weeks after starting treatment; every 1 to 2 months for first year of life; every 2 to 3 months during years 1 to 3; every 3 to 12 months until growth completed.

Nursing Physical Assessment/Monitoring

Check labs and report any abnormalities. Monitor vital signs closely, as well as signs of heart disease. Monitor mental and physical growth and development in pediatric patients. Monitor for and instruct patients to report any signs/symptoms of hyperthyroidism (weight loss, nervousness, sweating, tachycardia, insomnia, heat intolerance, palpitations, vomiting, psychosis, fever, seizures, angina, arrhythmias). Instruct patients with diabetes to monitor glucose levels closely (may increase need for oral hypoglycemics or insulin). Instruct patients not to change levothyroxine products without talking to healthcare provider.

Dosage Forms: US

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Capsule, Oral:

Tirosint: 175 mcg, 200 mcg

Capsule, Oral, as sodium:

Tirosint: 13 mcg, 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg

Solution, Oral, as sodium:

Tirosint-SOL: 13 mcg/mL (1 mL); 25 mcg/mL (1 mL); 50 mcg/mL (1 mL); 75 mcg/mL (1 mL); 88 mcg/mL (1 mL); 100 mcg/mL (1 mL); 112 mcg/mL (1 mL); 125 mcg/mL (1 mL); 137 mcg/mL (1 mL); 150 mcg/mL (1 mL); 175 mcg/mL (1 mL); 200 mcg/mL (1 mL)

Solution Reconstituted, Intravenous, as sodium [preservative free]:

Generic: 100 mcg (1 ea); 200 mcg (1 ea); 500 mcg (1 ea)

Tablet, Oral, as sodium:

Euthyrox: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg [contains corn starch]

Levoxyl: 25 mcg [scored; contains fd&c yellow #6 aluminum lake]

Levoxyl: 50 mcg [scored]

Levoxyl: 75 mcg [scored; contains fd&c blue #1 aluminum lake]

Levoxyl: 88 mcg [scored; contains fd&c blue #1 aluminum lake, fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Levoxyl: 100 mcg [scored; contains fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Levoxyl: 112 mcg [scored; contains fd&c red #40 aluminum lake, fd&c yellow #6 aluminum lake]

Levoxyl: 125 mcg [scored; contains fd&c red #40 aluminum lake, fd&c yellow #10 aluminum lake]

Levoxyl: 137 mcg, 150 mcg [scored; contains fd&c blue #1 aluminum lake]

Levoxyl: 175 mcg [scored; contains fd&c blue #1 aluminum lake, fd&c yellow #10 aluminum lake]

Levoxyl: 200 mcg [scored; contains fd&c yellow #10 aluminum lake]

Synthroid: 25 mcg [scored; contains fd&c yellow #6 aluminum lake]

Synthroid: 50 mcg [scored; contains corn starch]

Synthroid: 75 mcg [scored; contains corn starch, fd&c blue #2 aluminum lake, fd&c red #40 aluminum lake]

Synthroid: 88 mcg [scored; contains corn starch, fd&c blue #1 aluminum lake, fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Synthroid: 100 mcg [scored; contains corn starch, fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Synthroid: 112 mcg [scored; contains corn starch]

Synthroid: 125 mcg [scored; contains corn starch, fd&c blue #1 aluminum lake, fd&c red #40 aluminum lake, fd&c yellow #6 aluminum lake]

Synthroid: 137 mcg [scored; contains fd&c blue #1 aluminum lake]

Synthroid: 150 mcg [scored; contains fd&c blue #2 aluminum lake]

Synthroid: 175 mcg [scored; contains fd&c blue #1 aluminum lake]

Synthroid: 200 mcg [scored; contains fd&c red #40 aluminum lake]

Synthroid: 300 mcg [scored; contains fd&c blue #1 aluminum lake, fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Unithroid: 25 mcg [contains fd&c yellow #6 aluminum lake]

Unithroid: 50 mcg

Unithroid: 75 mcg [contains fd&c blue #2 aluminum lake, fd&c red #40 aluminum lake]

Unithroid: 88 mcg [contains fd&c blue #1 aluminum lake, fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Unithroid: 100 mcg [contains fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Unithroid: 112 mcg

Unithroid: 125 mcg [contains fd&c blue #1 aluminum lake, fd&c red #40 aluminum lake, fd&c yellow #6 aluminum lake]

Unithroid: 137 mcg [contains fd&c blue #1 aluminum lake]

Unithroid: 150 mcg [contains fd&c blue #2 aluminum lake]

Unithroid: 175 mcg [contains fd&c blue #1 aluminum lake]

Unithroid: 200 mcg [contains fd&c red #40 aluminum lake]

Unithroid: 300 mcg [contains fd&c blue #1 aluminum lake, fd&c yellow #10 (quinoline yellow), fd&c yellow #6 aluminum lake]

Unithroid Direct: 25 mcg [scored; contains fd&c yellow #6 aluminum lake]

Unithroid Direct: 50 mcg [scored]

Unithroid Direct: 75 mcg, 88 mcg [scored; contains fd&c blue #1 aluminum lake, fd&c blue #2 aluminum lake, fd&c red #40 aluminum lake, fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Unithroid Direct: 100 mcg [scored; contains fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Unithroid Direct: 112 mcg [scored]

Unithroid Direct: 125 mcg [scored; contains fd&c blue #1 aluminum lake, fd&c red #40 aluminum lake, fd&c yellow #6 aluminum lake]

Unithroid Direct: 150 mcg [scored; contains fd&c blue #2 aluminum lake]

Unithroid Direct: 175 mcg [scored; contains fd&c blue #1 aluminum lake]

Unithroid Direct: 200 mcg [scored; contains fd&c red #40 aluminum lake]

Unithroid Direct: 300 mcg [scored; contains fd&c blue #1 aluminum lake, fd&c yellow #10 aluminum lake, fd&c yellow #6 aluminum lake]

Generic: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg

Dosage Forms: Canada

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Solution Reconstituted, Injection, as sodium:

Synthroid: 500 mcg (1ea, 10ea)

Generic: 500 mcg (1ea, 5ml, 10ml)

Tablet, Oral, as sodium:

Euthyrox: 25 mcg [contains FD&C RED #40 ALUMINUM LAKE, FD&C YELLOW #10 ALUMINUM LAKE, FD&C YELLOW #6 ALUMINUM LAKE]

Euthyrox: 50 mcg

Euthyrox: 75 mcg [contains FD&C BLUE #1 ALUMINUM LAKE, FD&C BLUE #2 ALUMINUM LAKE, FD&C RED #40 ALUMINUM LAKE, FD&C YELLOW #6 ALUMINUM LAKE]

Euthyrox: 88 mcg [contains FD&C BLUE #2 ALUMINUM LAKE, FD&C YELLOW #5 ALUMINUM LAKE]

Euthyrox: 100 mcg [contains FD&C YELLOW #10 ALUMINUM LAKE, FD&C YELLOW #6 ALUMINUM LAKE]

Euthyrox: 112 mcg

Euthyrox: 125 mcg [contains FD&C BLUE #1 ALUMINUM LAKE, FD&C BLUE #2 ALUMINUM LAKE, FD&C RED #40 ALUMINUM LAKE, FD&C YELLOW #5 ALUMINUM LAKE, FD&C YELLOW #6 ALUMINUM LAKE]

Euthyrox: 137 mcg [contains FD&C BLUE #1 ALUMINUM LAKE]

Euthyrox: 150 mcg, 175 mcg [contains FD&C BLUE #2 ALUMINUM LAKE]

Euthyrox: 200 mcg

Euthyrox: 300 mcg [contains FD&C BLUE #1 ALUMINUM LAKE, FD&C YELLOW #10 ALUMINUM LAKE, FD&C YELLOW #6 ALUMINUM LAKE]

Synthroid: 25 mcg [contains FD&C YELLOW #6 (SUNSET YELLOW)]

Synthroid: 50 mcg

Synthroid: 75 mcg [contains FD&C BLUE #2 (INDIGOTINE), FD&C RED #40]

Synthroid: 88 mcg [contains BRILLIANT BLUE FCF (FD&C BLUE #1), FD&C YELLOW #10 (QUINOLINE YELLOW), FD&C YELLOW #6 (SUNSET YELLOW)]

Synthroid: 100 mcg [contains FD&C YELLOW #10 (QUINOLINE YELLOW), FD&C YELLOW #6 (SUNSET YELLOW)]

Synthroid: 112 mcg

Synthroid: 125 mcg [contains BRILLIANT BLUE FCF (FD&C BLUE #1), FD&C RED #40, FD&C YELLOW #6 (SUNSET YELLOW)]

Synthroid: 137 mcg [contains BRILLIANT BLUE FCF (FD&C BLUE #1)]

Synthroid: 150 mcg [contains FD&C BLUE #2 (INDIGOTINE)]

Synthroid: 175 mcg [contains BRILLIANT BLUE FCF (FD&C BLUE #1)]

Synthroid: 200 mcg [contains FD&C RED #40]

Synthroid: 300 mcg [contains BRILLIANT BLUE FCF (FD&C BLUE #1), FD&C YELLOW #10 (QUINOLINE YELLOW), FD&C YELLOW #6 (SUNSET YELLOW)]

Generic: 50 mcg, 100 mcg, 150 mcg, 200 mcg, 300 mcg [DSC]

Anatomic Therapeutic Chemical (ATC) Classification
  • H03AA01
Generic Available (US)

May be product dependent

Pricing: US

Capsules (Tirosint Oral)

13 mcg (per each): $5.12

25 mcg (per each): $5.12

50 mcg (per each): $5.12

75 mcg (per each): $5.12

88 mcg (per each): $5.12

100 mcg (per each): $5.12

112 mcg (per each): $5.12

125 mcg (per each): $5.12

137 mcg (per each): $5.12

150 mcg (per each): $5.12

175 mcg (per each): $5.12

200 mcg (per each): $5.12

Solution (Tirosint-SOL Oral)

13 mcg/mL (per mL): $5.12

25 mcg/mL (per mL): $5.12

50 mcg/mL (per mL): $5.12

75 mcg/mL (per mL): $5.12

88 mcg/mL (per mL): $5.12

100 mcg/mL (per mL): $5.12

112 mcg/mL (per mL): $5.12

125 mcg/mL (per mL): $5.12

137 mcg/mL (per mL): $5.12

150 mcg/mL (per mL): $5.12

175 mcg/mL (per mL): $5.12

200 mcg/mL (per mL): $5.12

Solution (reconstituted) (Levothyroxine Sodium Intravenous)

100 mcg (per each): $110.17 – $149.64

200 mcg (per each): $228.42 – $264.00

500 mcg (per each): $570.78 – $633.49

Tablets (Euthyrox Oral)

25 mcg (per each): $0.44

50 mcg (per each): $0.50

75 mcg (per each): $0.55

88 mcg (per each): $0.56

100 mcg (per each): $0.56

112 mcg (per each): $0.65

125 mcg (per each): $0.66

137 mcg (per each): $0.67

150 mcg (per each): $0.68

175 mcg (per each): $0.81

200 mcg (per each): $0.81

Tablets (Levo-T Oral)

25 mcg (per each): $0.44

50 mcg (per each): $0.50

75 mcg (per each): $0.55

88 mcg (per each): $0.56

100 mcg (per each): $0.56

112 mcg (per each): $0.65

125 mcg (per each): $0.66

137 mcg (per each): $0.67

150 mcg (per each): $0.68

175 mcg (per each): $0.81

200 mcg (per each): $0.81

300 mcg (per each): $1.04

Tablets (Levothyroxine Sodium Oral)

25 mcg (per each): $0.44 – $0.46

50 mcg (per each): $0.50 – $0.52

75 mcg (per each): $0.55 – $0.57

88 mcg (per each): $0.56

100 mcg (per each): $0.56 – $0.59

112 mcg (per each): $0.65

125 mcg (per each): $0.66 – $0.69

137 mcg (per each): $0.67

150 mcg (per each): $0.68 – $0.71

175 mcg (per each): $0.81

200 mcg (per each): $0.81

300 mcg (per each): $1.09

Tablets (Levoxyl Oral)

25 mcg (per each): $0.84

50 mcg (per each): $0.95

75 mcg (per each): $1.05

88 mcg (per each): $1.07

100 mcg (per each): $1.07

112 mcg (per each): $1.24

125 mcg (per each): $1.26

137 mcg (per each): $1.28

150 mcg (per each): $1.30

175 mcg (per each): $1.54

200 mcg (per each): $1.54

Tablets (Synthroid Oral)

25 mcg (per each): $1.49

50 mcg (per each): $1.49

75 mcg (per each): $1.49

88 mcg (per each): $1.49

100 mcg (per each): $1.49

112 mcg (per each): $1.49

125 mcg (per each): $1.49

137 mcg (per each): $1.49

150 mcg (per each): $1.49

175 mcg (per each): $1.48

200 mcg (per each): $1.49

300 mcg (per each): $1.49

Tablets (Unithroid Oral)

25 mcg (per each): $3.15

50 mcg (per each): $3.15

75 mcg (per each): $3.16

88 mcg (per each): $3.16

100 mcg (per each): $3.17

112 mcg (per each): $3.18

125 mcg (per each): $3.18

137 mcg (per each): $3.18

150 mcg (per each): $3.19

175 mcg (per each): $3.19

200 mcg (per each): $3.19

300 mcg (per each): $3.20

Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer’s AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.

Mechanism of Action

Levothyroxine (T4) is a synthetic form of thyroxine, an endogenous hormone secreted by the thyroid gland. T4 is converted to its active metabolite, L-triiodothyronine (T3). Thyroid hormones (T4 and T3) then bind to thyroid receptor proteins in the cell nucleus and exert metabolic effects through control of DNA transcription and protein synthesis; involved in normal metabolism, growth, and development; promotes gluconeogenesis, increases utilization and mobilization of glycogen stores, and stimulates protein synthesis, increases basal metabolic rate

Pharmacodynamics/Kinetics

Onset of action: Oral: 3 to 5 days; peak therapeutic effect may require 4 to 6 weeks; IV: Within 6 to 8 hours

Absorption: Oral: Erratic (40% to 80% [per manufacturer]); reported bioavailability in fasting state is 79% to 81% (Dickerson 2010; Fish 1987). Absorption may be decreased by age and specific foods and drugs.

Protein binding: >99% bound to plasma proteins including thyroxine-binding globulin, thyroxine-binding prealbumin, and albumin

Metabolism: Hepatic to triiodothyronine (T3; active); ~80% thyroxine (T4) deiodinated in kidney and periphery; glucuronidation/conjugation also occurs; undergoes enterohepatic recirculation

Time to peak, serum: 2 to 4 hours

Half-life elimination: Euthyroid: 6 to 7 days; Hypothyroid: 9 to 10 days; Hyperthyroid: 3 to 4 days

Excretion: Urine (major route of elimination; decreases with age); feces (~20%)

Local Anesthetic/Vasoconstrictor Precautions

No precautions with vasoconstrictor are necessary if patient is well controlled with levothyroxine

Effects on Dental Treatment

No significant effects or complications reported

Effects on Bleeding

No information available to require special precautions

Index Terms

L-Thyroxine Sodium; Levothroid; Levothyroxine Sodium; T4; Tirosint-Sol

References

American Academy of Pediatrics, Rose SR, Section on Endocrinology and Committee on Genetics, American Thyroid Association, et al. Update of Newborn Screening and Therapy for Congenital Hypothyroidism. Pediatrics. 2006;117(6):2290-2303.[PubMed 16740880]

Bauer LA, “Simulations of Levothyroxine Bioavailability Using a Single Dose Protocol,” Am J Ther, 1995, 2:414-6.[PubMed 11850686]

Berkner PD, Starkman H, and Person N, “Acute L-Thyroxine Overdose: Therapy With Sodium Ipodate: Evaluation of Clinical and Physiologic Parameters,” J Emerg Med, 1991, 9(3):129-31.[PubMed 2050969]

Binimelis J, Bassas L, Marruecos L, et al. Massive thyroxine intoxication: evaluation of plasma extraction. Intensive Care Med. 1987;13(1):33-38.[PubMed 3558934]

Carswell JM, Gordon JH, Popovsky E, Hale A, Brown RS. Generic and brand-name L-thyroxine are not bioequivalent for children with severe congenital hypothyroidism. J Clin Endocrinol Metab. 2013;98(2):610-617. doi: 10.1210/jc.2012-3125.[PubMed 23264396]

Cytomel (liothyronine) [prescribing information]. New York, NY: Pfizer Inc; June 2016.

de Groot JW, Zonnenberg BA, Plukker JT, et al, “Imatinib Induces Hypothyroidism in Patients Receiving Levothyroxine,” Clin Pharmacol Ther, 2005, 78(4):433-8.[PubMed 16198662]

Dickerson DN, Maish GO 3rd, Minard G, et al, “Clinical Relevancy of Levothyroxine – Continuous Enteral Nutrition Interaction,” Nutr Clin Pract, 2010, 25(6):646-52.[PubMed 21139130]

Eltroxin (levothyroxine) [product monograph]. Toronto, Ontario, Canada: Aspen Pharmacare Canada; January 2019.

Escalante DA, Arem N, and Arem R, “Assessment of Interchangeability of Two Brands of Levothyroxine Preparations With a Third-Generation TSH Assay,” Am J Med, 1995, 98(4):374-8.[PubMed 7709950]

Farwell AP. Sporadic Painless, Painful Subacute and Acute Infectious Thyroiditis. In: Braverman LE, Cooper DS. Werner & Ingbar’s The Thyroid: A Fundamental and Clinical Text. 10th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:418-422.

Fish LH, Schwartz HL, Cavanaugh J, Steffes MW, Bantle JP, Oppenheimer JH. Replacement dose, metabolism, and bioavailability of levothyroxine in the treatment of hypothyroidism. Role of triiodothyronine in pituitary feedback in humans. N Engl J Med. 1987;316(13):764-770.[PubMed 3821822]

Fleseriu M, Hashim IA, Karavitaki N, et al. Hormonal replacement in hypopituitarism in adults: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2016;101(11):3888–3921. doi: 10.1210/jc.2016-2118.[PubMed 27736313]

Francis GL, Waguespack SG, Bauer AJ, et al. Management guidelines for children with thyroid nodules and differentiated thyroid cancer. Thyroid. 2015;25(7):716-759.[PubMed 25900731]

Garber KR, Cobin RH, Gharib H, et al; American Association of Clinical Endocrinologists and American Thyroid Association Taskforce on Hypothyroidism in Adults. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012;18(6):988-1028.[PubMed 23246686]

Gharib H, Papini E, Garber JR, et al; AACE/ACE/AME Task Force on Thyroid Nodules. American Association of Clinical Endocrinologists, American College of Endocrinology, and Associazione Medici Endocrinologi medical guidelines for clinical practice for the diagnosis and management of thyroid nodules–2016 update. Endocr Pract. 2016;22(5):622-639. doi: 10.4158/EP161208.GL.[PubMed 27167915]

Gorman RL, Chamberlain JM, Rose SR, et al, “Massive Levothyroxine Overdose: High Anxiety – Low Toxicity,” Pediatrics, 1988, 82(4):666-9.[PubMed 3174321]

Gupta VD, “Stability of Levothyroxine Sodium Injection in Polypropylene Syringes,” Int J Pharm Compound, 2000, 4(6):482-3.

Helfand M and Crapo LM, “Monitoring Therapy in Patients Taking Levothyroxine,” Ann Intern Med, 1990, 113(6):450-4.[PubMed 2143640]

Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer: the American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid. 2016;26(1):1-133. doi: 10.1089/thy.2015.0020.[PubMed 26462967]

Ito S, Blajchman A, Stephenson M, Eliopoulos C, Koren G. Prospective follow-up of adverse reactions in breast-fed infants exposed to maternal medication. Am J Obstet Gynecol. 1993;168(5):1393-1399.[PubMed 8498418]

Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement. Thyroid. 2014;24(12):1670-1751.[PubMed 25266247]

Johnson DG and Campbell S, “Hormonal and Metabolic Agents,” Geriatric Pharmacology, Bressler R and Katz MD, eds, New York, NY: McGraw-Hill, 1993, 427-50.

Joseph B, Aziz H, Pandit V, et al. Levothyroxine therapy before brain death declaration increases the number of solid organ donations. J Trauma Acute Care Surg. 2014;76(5):1301-1305.[PubMed 24747464]

Kulig K, Golightly LK, and Rumack BH, “Levothyroxine Overdose Associated With Seizures in a Young Child,” JAMA, 1985, 254(15):2109-10.[PubMed 4046139]

Léger J, Olivieri A, Donaldson M, et al; ESPE-PES-SLEP-JSPE-APEG-APPES-ISPAE; Congenital Hypothyroidism Consensus Conference Group. European Society for Paediatric Endocrinology consensus guidelines on screening, diagnosis, and management of congenital hypothyroidism. Horm Res Paediatr. 2014;81(2):80-103. doi: 10.1159/000358198.[PubMed 24662106]

Levothyroxine sodium for injection [prescribing information]. Lake Zurich, IL: Fresenius Kabi USA LLC; April 2016.

Levoxyl (levothyroxine sodium) [prescribing information]. New York, NY: Pfizer; December 2018.

Liwanpo L and Hershman JM, “Conditions and Drugs Interfering With Thyroxine Absorption,” Best Pract Res Clin Endocrinol Metab, 2009, 23(6):781-92.[PubMed 19942153]

Mandel SH, Magnusson AR, Burton BT, et al, “Massive Levothyroxine Ingestion: Conservative Management,” Clin Pediatr (Phila), 1989, 28(8):374-6.[PubMed 2758719]

Mariani LH, Berns JS. The renal manifestations of thyroid disease. J Am Soc Nephrol. 2012;23(1):22-26. doi: 10.1681/ASN.2010070766.[PubMed 22021708]

Mayor GH, Orlando T, and Kurtz N, “Limitations of Levothyroxine Bioequivalence Evaluation: Analysis of an Attempted Study,” Am J Ther, 1995, 2:417-32.[PubMed 11850687]

Nakagawa TA, “Updated Pediatric Donor Management and Dosing Guidelines,” 2008. Available at http://www.natco1.org/prof_development/documents/FINALNATCOPedDonorManagementGuidelines_Jan08.pdf. Last accessed June 2012.

Parle JV, Maisonneuve P, Sheppard MC, et al, “Prediction of All-Cause and Cardiovascular Mortality in Elderly People from One Low Serum Thyrotropin Result: A 10-year Cohort Study,” Lancet, 2001, 358(9285):861-5.[PubMed 11567699]

Pearce SH, Brabant G, Duntas LH, et al. 2013 ETA Guideline: Management of Subclinical Hypothyroidism. Eur Thyroid J. 2013;2(4):215-228.[PubMed 24783053]

Rosendale JD, Kauffman HM, McBride MA, et al, “Aggressive Pharmacologic Donor Management Results in More Transplanted Organs,” Transplantation, 2003a, 75(4):482-7.[PubMed 12605114]

Rosendale JD, Kauffman HM, McBride MA, et al. Hormonal resuscitation yields more transplanted hearts, with improved early function. Transplantation. 2003b;75(8):1336-1341.[PubMed 12717226]

Rosengard BR, Feng S, Alfrey EJ, et al, “Report of the Crystal City Meeting to Maximize the Use of Organs Recovered From the Cadaver Donor,” Am J Transplant, 2002, 2(8):701-11.[PubMed 12243491]

Salim A, Martin M, Brown C, et al. Using thyroid hormone in brain-dead donors to maximize the number of organs available for transplantation.Clin Transplant, 2007;21(3):405-409.[PubMed 17488392 ]

Sanders LR, “Pituitary, Thyroid, Adrenal and Parathyroid Diseases in the Elderly,” Geriatric Medicine, 1990, 475-87.

Sawin CT, Geller A, Hershman JM, et al, “The Aging Thyroid. The Use of Thyroid Hormone in Older Persons,” JAMA, 1989, 261(18):2653-5.[PubMed 2709545]

Schneider DL, Barrett-Connor EL, Morton DJ. Thyroid hormone use and bone mineral density in elderly women. Effects of estrogen. JAMA. 1994;271(16):1245-1249.[PubMed 7848399]

Selva KA, Mandel SH, Rien L, et al. Initial Treatment Dose of L-thyroxine in Congenital Hypothyroidism. J Pediatr. 2002;141(6):786-792.[PubMed 12461494]

Singh N, Singh P, and Hershman J. “Effect of Calcium Carbonate on the Absorption of Levothyroxine,” JAMA, 2000, 283:2822-25.[PubMed 10838651]

Stagnaro-Green A, Abalovich M, Alexander E, et al; American Thyroid Association Taskforce on Thyroid Disease During Pregnancy and Postpartum, Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011;21(10):1081-1125.[PubMed 21787128]

Strong DK, Decarie D, and Ensom MHH, “Stability of Levothyroxine in Sodium Chloride for IV Administration,” Can J Hosp Pharm, 2010, 63(6):437-43.

Syed Q, Hendler KT, Koncilja K. The impact of aging and medical status on dysgeusia. Am J Med. 2016;129(7):753.[PubMed 26899755]

Synthroid (levothyroxine) [prescribing information]. North Chicago, IL: AbbVie Inc; November 2018.

Synthroid (levothyroxine) [product monograph]. St-Laurent, Quebec, Canada: BGP Pharma ULC; May 2015.

Tirosint (levothyroxine) [prescribing information]. Cranford, NJ: Akrimax Pharmaceuticals; June 2018.

Tirosint-Sol (levothyroxine) [US prescribing information]. Pambio-Noranco, Switzerland: IBSA Institut Biochimique SA; June 2018.

Tunget CL, Clark RF, Turchen SG, et al, “Raising the Decontamination Level for Thyroid Hormone Ingestions,” Am J Emerg Med, 1995, 13(1):9-13.[PubMed 7832964]

Unithroid (levothyroxine sodium) [prescribing information]. Bridgewater, NJ: Gemini Laboratories; December 2018.

van Wassenaer AG, Stulp MR, Valianpour F, et al, The quantity of thyroid hormone in human milk Is too low to influence plasma thyroid hormone levels in the very preterm infant. Clin Endocrinol (Oxf). 2002;56(5):621-627.[PubMed 12030913]

Watts NB, “Use of a Sensitive Thyrotropin Assay for Monitoring Treatment With Levothyroxine,” Arch Intern Med, 1989, 149(2):309-12.[PubMed 2644903]

Zaroff JG, Rosengard BR, Armstrong WF, et al. Consensus Conference Report: Maximizing Use of Organs Recovered from the Cadaver Donor: Cardiac Recommendations: March 28-29, 2001, Crystal City, Va. Circulation. 2002;106(7):836-841.[PubMed 12176957]

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Brand Names: International

Accu-Thyrox (RO); Berlthyrox (DE); Cynocuatro (MX); Droxine (NZ); Eferox (BH, QA); Elthyro (TH); Eltroxin (AE, AU, BD, BF, BH, BJ, BM, BZ, CH, CI, CY, CZ, DK, ET, GB, GH, GM, GN, GY, HK, IE, IL, IQ, IR, JO, JP, KE, KW, LB, LR, LY, MA, ML, MR, MT, MU, MW, NE, NG, OM, PH, PK, QA, SA, SC, SD, SL, SN, SR, SY, TH, TN, TW, TZ, UG, YE, ZA, ZM, ZW); Eurolev (PH); Euthirox (UA); Euthyrox (AE, AR, AT, BE, BG, BH, BR, CH, CN, CY, CZ, DE, EE, EG, HR, HU, ID, IS, JO, KW, LB, LU, LV, MY, PH, PL, QA, RO, RU, SA, SE, SG, SI, SK, TH, TR, TZ, VE); Eutirox (BB, BS, CL, CR, CU, DO, ES, GT, HN, IT, JM, MX, NI, NL, PA, PE, SV, TT); Eutroxsig (AU, NZ); Levaxin (SE); Levhexal (MX); Levothyrox (FR); Levotirox (IT); Levotiroxina (EC); Narval (UY); Oroxine (AU, IE, MY); Pondtroxin (TH); Synox (IN); Synroid (BD); Synthroid (BH, BR, CO, KR, KW, NZ); Synthyroxine (KR); T4 (PY); T4KP (TH); Thevier (BE, DE); Thormon (BD); Throid (BD); Thydin (PH); Thynor (BD); Thyradin S (JP); Thyrax (BE, CZ, ID, PT); Thyrax Duotab (BF, BJ, CI, ET, GH, GM, GN, KE, LR, MA, ML, MR, MU, MW, NE, NG, SC, SD, SL, SN, TN, TZ, UG, ZM); Thyrex (AT); Thyro-4 (GR); Thyroid-S (TW); Thyromega (LK); Thyronorm (LK); Thyrosit (TH); Thyrox (LK); Thyroxin (FI); Thyvex (LK); Tiroidine (MX); Tiroxin (CO, EC); Tyraq (HR); Tyraxin (EG); Zaliana (PH)

Levothyroxine (Patient Education – Adult Medication)
You must carefully read the “Consumer Information Use and Disclaimer” below in order to understand and correctly use this information
Pronunciation

(lee voe thye ROKS een)

Brand Names: US

Euthyrox; Levoxyl; Synthroid; Tirosint; Tirosint-SOL; Unithroid; Unithroid Direct

Brand Names: Canada

Eltroxin; Synthroid

Warning
  • Do not use this drug to treat obesity or for weight loss. Very bad and sometimes deadly side effects may happen with this drug if it is taken in large doses or with other drugs for weight loss. Talk with the doctor.
What is this drug used for?
  • It is used to add thyroid hormone to the body.
  • It is used to manage thyroid cancer.
  • It may be given to you for other reasons. Talk with the doctor.
What do I need to tell my doctor BEFORE I take this drug?
  • All products:
  • If you have an allergy to levothyroxine or any other part of this drug.
  • If you are allergic to any drugs like this one, any other drugs, foods, or other substances. Tell your doctor about the allergy and what signs you had, like rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs.
  • If you have any of these health problems: Overactive thyroid gland or weak adrenal gland.
  • Tablets and capsules:
  • If you have trouble swallowing.
  • This is not a list of all drugs or health problems that interact with this drug.
  • Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take this drug with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.
What are some things I need to know or do while I take this drug?
  • For all patients taking this drug:
  • Tell all of your health care providers that you take this drug. This includes your doctors, nurses, pharmacists, and dentists.
  • Do not run out of this drug.
  • It may take several weeks to see the full effects.
  • If you have high blood sugar (diabetes), this drug may sometimes raise blood sugar. Talk with your doctor about how to keep your blood sugar under control.
  • Check your blood sugar as you have been told by your doctor.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • This drug may cause weak bones (osteoporosis) with doses that are too high. The risk may be higher in women who have been through menopause. Talk with your doctor to see if you have a higher risk of weak bones or if you have any questions.
  • This drug may affect how much of some other drugs are in your body. If you are taking other drugs, talk with your doctor. You may need to have your blood work checked more closely while taking this drug with your other drugs.
  • This drug may affect fertility. Fertility problems may lead to not being able to get pregnant or father a child. Talk with the doctor.
  • If you are 65 or older, use this drug with care. You could have more side effects.
  • Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using this drug while you are pregnant.
  • Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.
  • Children:
  • If giving to your child, the dose of this drug may need to be changed as your child’s weight changes. Have your child’s weight checked often. Talk with the doctor before changing your child’s dose.
  • This drug may affect growth in children and teens in some cases. They may need regular growth checks. Talk with the doctor.
What are some side effects that I need to call my doctor about right away?
  • WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:
  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of high blood pressure like very bad headache or dizziness, passing out, or change in eyesight.
  • Chest pain or pressure or a fast heartbeat.
  • A heartbeat that does not feel normal.
  • Shortness of breath, a big weight gain, or swelling in the arms or legs.
  • Headache.
  • Feeling tired or weak.
  • Feeling more or less hungry.
  • A change in weight without trying.
  • Diarrhea.
  • Stomach cramps.
  • Throwing up.
  • Feeling irritable.
  • Feeling nervous and excitable.
  • Anxiety.
  • Emotional ups and downs.
  • Shakiness.
  • Trouble sleeping.
  • Bothered by heat.
  • Sweating a lot.
  • Fever.
  • Leg cramps.
  • Muscle weakness.
  • Flushing.
  • Bone pain.
  • Period (menstrual) changes.
What are some other side effects of this drug?
  • All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:
  • Hair loss may happen in some people in the first few months of using this drug. This most often goes back to normal.
  • These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.
  • You may report side effects to your national health agency.
How is this drug best taken?
  • Use this drug as ordered by your doctor. Read all information given to you. Follow all instructions closely.
  • All oral products:
  • Take on an empty stomach at least 30 to 60 minutes before breakfast.
  • Do not take iron products, antacids that have aluminum or magnesium, or calcium carbonate, within 4 hours before or 4 hours after taking this drug.
  • If you take colesevelam, colestipol, cholestyramine, kayexalate, or sevelamer, take it at least 4 hours before or 4 hours after taking this drug.
  • Some other drugs may need to be taken at some other time than this drug. If you take other drugs, check with your doctor or pharmacist to see if you need to take them at some other time than this drug.
  • Some foods like soybean flour (infant formula) may change how this drug works in your body. Talk with your doctor.
  • If you drink grapefruit juice or eat grapefruit often, talk with your doctor.
  • To gain the most benefit, do not miss doses.
  • Keep taking this drug as you have been told by your doctor or other health care provider, even if you feel well.
  • Capsules:
  • Swallow capsule whole. Do not chew, break, or crush.
  • Tablets:
  • Some products may cause choking, gagging, or trouble swallowing. These products must be taken with a full glass of water. Ask your pharmacist if you need to take your product with a full glass of water.
  • You may crush tablet and mix with 1 or 2 teaspoons (5 or 10 mL) of water.
  • Tablets and capsules:
  • There is more than 1 brand of this drug. One brand cannot safely be used for the other. The doctor will tell you about any needed change.
  • Oral solution:
  • You may put this drug right in your mouth or you may mix it with water. If mixing with water, empty the contents into a cup with water in it. Squeeze the container over the cup at least 5 times until no more drug comes out. Stir well.
  • After mixing, take your dose right away. Do not store for future use.
  • Rinse cup with more water and drink.
  • Take with water only; do not take with other drinks.
  • Injection:
  • It is given as a shot into a vein.
What do I do if I miss a dose?
  • All oral products:
  • Take a missed dose as soon as you think about it.
  • If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
  • Do not take 2 doses at the same time or extra doses.
  • Injection:
  • Call your doctor to find out what to do.
How do I store and/or throw out this drug?
  • All oral products:
  • Store at room temperature.
  • Protect from heat and light.
  • Store in a dry place. Do not store in a bathroom.
  • Capsules:
  • Do not take this drug out of the blister pack until you are ready to take it. Take this drug right away after opening the blister pack. Do not store the removed drug for future use.
  • Tablets:
  • Some brands of this drug come in a blister pack. If this drug comes in a blister pack, do not take it out of the blister pack until you are ready to take it. Do not store the removed drug for future use.
  • Oral solution:
  • Store in protective pouch until ready for use.
  • Throw away 15 days after opening the pouch.
  • Injection:
  • If you need to store this drug at home, talk with your doctor, nurse, or pharmacist about how to store it.
  • All products:
  • Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
  • Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.
General drug facts
  • If your symptoms or health problems do not get better or if they become worse, call your doctor.
  • Do not share your drugs with others and do not take anyone else’s drugs.
  • Keep a list of all your drugs (prescription, natural products, vitamins, OTC) with you. Give this list to your doctor.
  • Talk with the doctor before starting any new drug, including prescription or OTC, natural products, or vitamins.
  • Some drugs may have another patient information leaflet. If you have any questions about this drug, please talk with your doctor, nurse, pharmacist, or other health care provider.
  • If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.
Levothyroxine (Patient Education – Pediatric Medication)
You must carefully read the “Consumer Information Use and Disclaimer” below in order to understand and correctly use this information
Pronunciation

(lee voe thye ROKS een)

Brand Names: US

Euthyrox; Levoxyl; Synthroid; Tirosint; Tirosint-SOL; Unithroid; Unithroid Direct

Brand Names: Canada

Eltroxin; Synthroid

Warning
  • Do not use this drug to treat obesity or for weight loss. Very bad and sometimes deadly side effects may happen with this drug if it is taken in large doses or with other drugs for weight loss. Talk with the doctor.
What is this drug used for?
  • It is used to add thyroid hormone to the body.
  • It is used to manage thyroid cancer.
  • It may be given to your child for other reasons. Talk with the doctor.
What do I need to tell the doctor BEFORE my child takes this drug?
  • All products:
  • If your child has an allergy to this drug or any part of this drug.
  • If your child is allergic to any drugs like this one or any other drugs, foods, or other substances. Tell the doctor about the allergy and what signs your child had, like rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs.
  • If your child has any of these health problems: Overactive thyroid gland or weak adrenal gland.
  • Tablets and capsules:
  • If your child has trouble swallowing.
  • This is not a list of all drugs or health problems that interact with this drug.
  • Tell the doctor and pharmacist about all of your child’s drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for your child to take this drug with all of his/her drugs and health problems. Do not start, stop, or change the dose of any drug your child takes without checking with the doctor.
What are some things I need to know or do while my child takes this drug?
  • Tell all of your child’s health care providers that your child is taking this drug. This includes your child’s doctors, nurses, pharmacists, and dentists.
  • Do not run out of this drug.
  • It may take several weeks to see the full effects.
  • If your child has high blood sugar (diabetes), this drug may sometimes raise blood sugar. Talk with your child’s doctor about how to keep your child’s blood sugar under control.
  • Have your child’s blood sugar checked as you have been told by your child’s doctor.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • This drug may cause weak bones (osteoporosis) with doses that are too high. Talk with your child’s doctor to see if your child has a higher risk of weak bones or if you have any questions.
  • This drug may affect how much of some other drugs are in the body. If your child is taking other drugs, talk with the doctor. Your child may need to have blood work checked more closely while taking this drug with other drugs.
  • If giving to your child, the dose of this drug may need to be changed as your child’s weight changes. Have your child’s weight checked often. Talk with the doctor before changing your child’s dose.
  • This drug may affect growth in children and teens in some cases. They may need regular growth checks. Talk with the doctor.
  • This drug may affect fertility. Fertility problems may lead to not being able to get pregnant or father a child. Talk with the doctor.
  • If your child is pregnant or breast-feeding a baby:
  • Talk with the doctor if your child is pregnant, becomes pregnant, or is breast-feeding a baby. You will need to talk about the benefits and risks to your child and the baby.
What are some side effects that I need to call my child’s doctor about right away?
  • WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your child’s doctor or get medical help right away if your child has any of the following signs or symptoms that may be related to a very bad side effect:
  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of high blood pressure like very bad headache or dizziness, passing out, or change in eyesight.
  • Chest pain or pressure or a fast heartbeat.
  • A heartbeat that does not feel normal.
  • Shortness of breath, a big weight gain, or swelling in the arms or legs.
  • Lump on the neck.
  • Headache.
  • Feeling tired or weak.
  • Feeling more or less hungry.
  • A change in weight without trying.
  • Diarrhea.
  • Stomach cramps.
  • Throwing up.
  • Feeling irritable.
  • Feeling nervous and excitable.
  • Anxiety.
  • Emotional ups and downs.
  • Shakiness.
  • Trouble sleeping.
  • Bothered by heat.
  • Sweating a lot.
  • Fever.
  • Leg cramps.
  • Muscle weakness.
  • Flushing.
  • Bone pain.
  • If your child has menstrual periods:
  • Period (menstrual) changes.
What are some other side effects of this drug?
  • All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your child’s doctor or get medical help if any of these side effects or any other side effects bother your child or do not go away:
  • Hair loss may happen in some people in the first few months of using this drug. This most often goes back to normal.
  • These are not all of the side effects that may occur. If you have questions about side effects, call your child’s doctor. Call your child’s doctor for medical advice about side effects.
  • You may report side effects to your national health agency.
How is this drug best given?
  • Give this drug as ordered by your child’s doctor. Read all information given to you. Follow all instructions closely.
  • All oral products:
  • Give on an empty stomach at least 30 to 60 minutes before breakfast.
  • Do not give your child iron products, antacids that have aluminum or magnesium, or calcium carbonate within 4 hours before or 4 hours after taking this drug.
  • If your child takes colesevelam, colestipol, cholestyramine, kayexalate, or sevelamer, do not give it within 4 hours before or 4 hours after your child takes this drug.
  • Some other drugs may need to be given at some other time than this drug. If your child takes other drugs, check with the doctor or pharmacist to see if you need to give them to your child at some other time than this drug.
  • Some foods like soybean flour (infant formula) may change how this drug works in your body. Talk with your doctor.
  • If your child drinks grapefruit juice or eats grapefruit often, talk with your child’s doctor.
  • To gain the most benefit, do not miss giving your child doses.
  • Keep giving this drug to your child as you have been told by your child’s doctor or other health care provider, even if your child feels well.
  • Capsules:
  • Have your child swallow whole. Do not let your child chew, break, or crush.
  • Tablets:
  • Some products may cause choking, gagging, or trouble swallowing. These products must be given with a full glass of water. Ask the pharmacist if your child needs to take this product with a full glass of water.
  • If your child cannot swallow pills, the tablet may be crushed and mixed in 1 to 2 teaspoons (5 to 10 mL) of water right before giving to your child.
  • Tablets and capsules:
  • There is more than 1 brand of this drug. One brand cannot safely be used for the other. The doctor will tell you about any needed change.
  • Oral solution:
  • You may put this drug right in your child’s mouth or you may mix it with water. If mixing with water, empty the contents into a cup with water in it. Squeeze the container over the cup at least 5 times until no more drug comes out. Stir well.
  • After mixing, give the dose right away. Do not store for future use.
  • Rinse cup with more water and have your child drink.
  • Give this drug with water only; do not give with other drinks.
  • Injection:
  • It is given as a shot into a vein.
What do I do if my child misses a dose?
  • All oral products:
  • Give a missed dose as soon as you think about it.
  • If it is close to the time for your child’s next dose, skip the missed dose and go back to your child’s normal time.
  • Do not give 2 doses at the same time or extra doses.
  • Injection:
  • Call your child’s doctor to find out what to do.
How do I store and/or throw out this drug?
  • All oral products:
  • Store at room temperature.
  • Protect from heat and light.
  • Store in a dry place. Do not store in a bathroom.
  • Capsules:
  • Do not take this drug out of the blister pack until you are ready to give this drug to your child. Give this drug right away after opening the blister pack. Do not store the removed drug for future use.
  • Tablets:
  • Some brands of this drug come in a blister pack. If this drug comes in a blister pack, do not take it out of the blister pack until you are ready to take it. Do not store the removed drug for future use.
  • Oral solution:
  • Store in protective pouch until ready for use.
  • Throw away 15 days after opening the pouch.
  • Injection:
  • If you need to store this drug at home, talk with your child’s doctor, nurse, or pharmacist about how to store it.
  • All products:
  • Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
  • Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.
General drug facts
  • If your child’s symptoms or health problems do not get better or if they become worse, call your child’s doctor.
  • Do not share your child’s drug with others and do not give anyone else’s drug to your child.
  • Keep a list of all your child’s drugs (prescription, natural products, vitamins, OTC) with you. Give this list to your child’s doctor.
  • Talk with your child’s doctor before giving your child any new drug, including prescription or OTC, natural products, or vitamins.
  • Some drugs may have another patient information leaflet. If you have any questions about this drug, please talk with your child’s doctor, nurse, pharmacist, or other health care provider.
  • If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.