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ALERT: U.S. Boxed Warning
The FDA-approved labeling includes a boxed warning. See Warnings/Precautions section for a concise summary of this information. For verbatim wording of the boxed warning, consult the product labeling or www.fda.gov.
Pronunciation
(lee voe thye ROKS een)
Generic Available (U.S.)
Yes
Index Terms
U.S. Brand Names
Canadian Brand Names
Pharmacologic Category
Use: Labeled Indications
Replacement or supplemental therapy in hypothyroidism; pituitary TSH suppression
Use: Unlabeled/Investigational
Management of hemodynamically unstable potential organ donors increasing the quantity of organs available for transplantation
Pregnancy Risk Factor
A
Pregnancy Considerations
Untreated maternal hypothyroidism may have adverse effects on fetal growth and development and is associated with higher rate of complications (spontaneous abortion, pre-eclampsia, stillbirth, premature delivery). Treatment should not be discontinued during pregnancy. TSH levels should be monitored during each trimester and 6-8 weeks postpartum. Increased doses may be needed during pregnancy.
Lactation
Enters breast milk/compatible
Breast-Feeding Considerations
Minimally excreted in human milk; adequate levels are needed to maintain normal lactation
Contraindications
Hypersensitivity to levothyroxine sodium or any component of the formulation; acute MI; thyrotoxicosis of any etiology; uncorrected adrenal insufficiency
Capsule: Additional contraindication: Inability to swallow capsules
Warnings/Precautions
Boxed warnings:
• Weight reduction: See “Other warnings/precautions” below.
Disease-related concerns:
• Adrenal insufficiency: Use with caution in patients with adrenal insufficiency; symptoms may be exaggerated or aggravated.
• Benign thyroid nodules: Appropriate use: Routine use of T4 for TSH suppression is not recommended in patients with benign thyroid nodules. Treatment should never be fully suppressive (TSH <0.1 mIU/L) (Gharib, 2010; Cooper, 2009).
- Use of T4 is often physician-dependent and may be considered in select patients, including patients who reside in iodine-deficient areas, young patients with small thyroid nodules, and patients with nonfunctioning nodular goiters (Gharib, 2010).
- Use should be avoided in postmenopausal women, men >60 years of age, patients with cardiovascular disease, osteoporosis, or systemic illness, and patients with large thyroid nodules or long-standing goiters, or low-normal TSH levels (Gharib, 2010).
• Cardiovascular disease: Use with caution and reduce dosage in patients with angina pectoris or other cardiovascular disease; chronic hypothyroidism predisposes patients to coronary artery disease.
• Diabetes: Use with caution in patients with diabetes mellitus and insipidus; symptoms may be exaggerated or aggravated.
• Myxedema: Use with caution in patients with myxedema; symptoms may be exaggerated or aggravated.
• Osteoporosis: Long-term therapy can decrease bone mineral density. Postmenopausal women and women using suppressive doses should receive the lowest dose necessary for clinical response.
Special populations:
• Elderly: Use with caution; decrease initial dose; suppressed TSH levels may increase risk of atrial fibrillation and mortality secondary to cardiovascular disease. (Gharib, 2010).
Dosage form specific issues:
• Levoxyl®: Product may rapidly swell and disintegrate causing choking or gagging (should be administered with a full glass of water); use caution in patients with dysphagia or other swallowing disorders.
Other warnings/precautions:
• Weight reduction: [U.S. 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).
Adverse Reactions
Frequency not defined.
Cardiovascular: Angina, arrhythmia, cardiac arrest, flushing, heart failure, hypertension, MI, palpitation, pulse increased, tachycardia
Central nervous system: Anxiety, emotional lability, fatigue, fever, headache, hyperactivity, insomnia, irritability, nervousness, pseudotumor cerebri (children), seizure (rare)
Dermatologic: Alopecia
Endocrine & metabolic: Fertility impaired, menstrual irregularities
Gastrointestinal: Abdominal cramps, appetite increased, diarrhea, vomiting, weight loss
Hepatic: Liver function tests increased
Neuromuscular & skeletal: Bone mineral density decreased, muscle weakness, tremor, slipped capital femoral epiphysis (children)
Respiratory: Dyspnea
Miscellaneous: Diaphoresis, heat intolerance, hypersensitivity (to inactive ingredients, symptoms include urticaria, pruritus, rash, flushing, angioedema, GI symptoms, fever, arthralgia, serum sickness, wheezing)
Levoxyl®: Choking, dysphagia, gagging
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
Bile Acid Sequestrants: May decrease the absorption of Thyroid Products. Risk C: Monitor therapy
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
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: Ferumoxytol; Iron Dextran Complex; 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
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
Phenytoin: May decrease the serum concentration of Thyroid Products. Phenytoin may also displace thyroid hormones from protein binding sites. Risk C: Monitor therapy
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
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
Sucralfate: May decrease the serum concentration of Levothyroxine. Risk C: Monitor therapy
Theophylline Derivatives: Thyroid Products may increase the metabolism of Theophylline Derivatives. Exceptions: Dyphylline. Risk C: Monitor therapy
Vitamin K Antagonists (eg, warfarin): Thyroid Products may enhance the anticoagulant effect of Vitamin K Antagonists. Risk D: Consider therapy modification
Ethanol/Nutrition/Herb Interactions
Food: 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), cottonseed meal, walnuts, and dietary fiber may decrease absorption of levothyroxine from the GI tract.
Storage
Store capsules, tablets, and injection at room temperature; excursions permitted to 15°C to 30°C (59°F to 86°F). Protect from light and moisture.
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).
Reconstitution
Dilute vial for injection with 5 mL normal saline. Reconstituted concentrations for the 200 mcg and 500 mcg vials are 40 mcg/mL and 100 mcg/mL, respectively. Shake well and use immediately after reconstitution (manufacturer recommendation); discard any unused portions.
Compatibility
Do not mix I.V. solution with other I.V. infusion solutions.
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: Therapeutic: Oral: 3-5 days; I.V. 6-8 hours
Peak effect: I.V.: 24 hours
Absorption: Oral: Erratic (40% to 80%); 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 (active); T4 deiodination in kidney and periphery; glucuronidation/conjugation also occurs; undergoes enterohepatic recirculation
Time to peak, serum: 2-4 hours
Half-life elimination: Euthyroid: 6-7 days; Hypothyroid: 9-10 days; Hyperthyroid: 3-4 days
Excretion: Urine (major route of elimination; decreases with age); feces (~20%)
Dosage
Doses should be adjusted based on clinical response and laboratory parameters.
Oral:
Neonates, Infants, and Children: Hypothyroidism: Daily dosage based on body weight and age as listed below:
0-3 months: 10-15 mcg/kg/day; if the infant is at risk for development of cardiac failure, use a lower starting dose of 25 mcg/day; if the initial serum T4 is very low (<5 mcg/dL) begin treatment at a higher dosage of 50 mcg/day
3-6 months: 8-10 mcg/kg/day or 25-50 mcg/day
6-12 months: 6-8 mcg/kg/day or 50-75 mcg/day
1-5 years: 5-6 mcg/kg/day or 75-100 mcg/day
6-12 years: 4-5 mcg/kg/day or 100-125 mcg/day
>12 years: 2-3 mcg/kg/day or ≥150 mcg/day
Growth and puberty complete: 1.7 mcg/kg/day; refer to Adult dosing.
Dosing modifications:
Hyperactivity in older children may be minimized by starting at 1/4 of the recommended dose and increasing each week by that amount until the full dose is achieved (4 weeks).
Children with severe or chronic hypothyroidism should be started at 25 mcg/day; adjust dose by 25 mcg every 2-4 weeks.
Adults (including children in whom growth and puberty are complete, healthy adults <50 years of age, and older adults who have been recently treated for hyperthyroidism or who have been hypothyroid for only a few months):
Hypothyroidism: ~1.7 mcg/kg/day; usual doses are ≤200 mcg/day (range: 100-125 mcg/day [70 kg adult]); doses ≥300 mcg/day are rare (consider poor compliance, malabsorption, and/or drug interactions). Titrate dose every 6 weeks.
Patients >50 years or patients with cardiac disease: Refer to Elderly dosing.
Severe hypothyroidism: Initial: 12.5-25 mcg/day; adjust dose by 25 mcg/day every 2-4 weeks as appropriate
Myxedema: Oral agents are not recommended for myxedema: Refer to I.V. dosing.
Subclinical hypothyroidism (if treated): 1 mcg/kg/day
TSH suppression:
Well-differentiated thyroid cancer: Highly individualized; Doses >2 mcg/kg/day may be needed to suppress TSH to <0.1 mIU/L in intermediate- to high-risk tumors. Low-risk tumors may be maintained at or slightly below the lower limit of normal (0.1-0.5 mIU/L) (Cooper, 2009).
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 mIU/L) (Cooper, 2009; Gharib, 2010). Avoid use if TSH is already suppressed.
Elderly: Hypothyroidism (elderly patients may require <1 mcg/kg/day):
>50 years without cardiac disease or <50 years with cardiac disease: Initial: 25-50 mcg/day; adjust dose by 12.5-25 mcg increments at 6- to 8-week intervals as needed
>50 years with cardiac disease: Initial: 12.5-25 mcg/day; adjust dose by 12.5-25 mcg increments at 4- to 6-week intervals (many clinicians prefer to adjust at 6- to 8-week intervals)
Note: Patients with combined hypothyroidism and cardiac disease should be monitored carefully for changes in stability.
I.M., I.V.: Children, Adults, Elderly: Hypothyroidism: 50% of the oral dose
I.V.:
Adults: Myxedema coma or stupor: 200-500 mcg, then 100-300 mcg the next day if necessary; smaller doses should be considered in patients with cardiovascular disease
Elderly: Myxedema coma: Refer to adult dosing; lower doses may be needed
Administration: Oral
Administer in the morning on an empty stomach, at least 30 minutes before food.
Capsule: Must be swallowed whole; do not cut, crush, or attempt to dissolve capsules in water to prepare a suspension
Tablet: May be crushed and suspended in 1-2 teaspoonfuls of water; suspension should be used immediately. Levoxyl® should be administered with a full glass of water to prevent gagging (due to tablet swelling).
Administration: I.V.
Dilute vial with 5 mL normal saline; use immediately after reconstitution; do not mix with other I.V. fluids
Administration: Other
Nasogastric tube: Bioavailability of levothyroxine 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).
Administration: I.V. Detail
Dilute vial with 5 mL normal saline. Use immediately after reconstitution. I.V. form must be prepared immediately prior to administration. Should not be admixed with other solutions.
Monitoring Parameters
Thyroid function test (serum thyroxine, thyrotropin concentrations), resin triiodothyronine uptake (rT3U), free thyroxine index (FTI), T4, TSH, heart rate, blood pressure, clinical signs of hypo- and hyperthyroidism; TSH is the most reliable guide for evaluating adequacy of thyroid replacement dosage. 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
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 1-2 months for first year of life; every 2-3 months during years 1-3; every 3-12 months until growth completed. Perform routine clinical examinations at regular intervals (to assess mental and physical growth and development).
Adults: Monitor TSH every 6-8 weeks until normalized; 8-12 weeks after dosage changes; every 6-12 months throughout therapy
Reference Range
Pediatrics: Cord T4 and values in the first few weeks are much higher, falling over the first months and years. ≥10 years: ~5.8-11 mcg/dL (SI: 75-142 nmol/L). Borderline low: ≤4.5-5.7 mcg/dL (SI: 58-73 nmol/L); low: ≤4.4 mcg/dL (SI: 57 nmol/L); results <2.5 mcg/dL (SI: <32 nmol/L) are strong evidence for hypothyroidism.
Approximate adult normal range: 4-12 mcg/dL (SI: 51-154 nmol/L). Borderline high: 11.1-13 mcg/dL (SI: 143-167 nmol/L); high: ≥13.1 mcg/dL (SI: 169 nmol/L). Normal range is increased in women on birth control pills (5.5-12 mcg/dL); normal range in pregnancy: ~5.5-16 mcg/dL (SI: ~71-206 nmol/L). TSH: 0.4-10 (for those ≥80 years) mIU/L; T4: 4-12 mcg/dL (SI: 51-154 nmol/L); T3 (RIA) (total T3): 80-230 ng/dL (SI: 1.2-3.5 nmol/L); T4 free (free T4): 0.7-1.8 ng/dL (SI: 9-23 pmol/L).
Test Interactions
Many drugs may have effects on thyroid function tests (see Additional Information or Pharmacotherapy Pearls). Pregnancy, infectious hepatitis, and acute intermittent porphyria may increase TBG concentrations; nephrosis, severe hypoproteinemia, severe liver disease, and acromegaly may decrease TBG concentrations.
Dietary Considerations
Should be taken on an empty stomach, at least 30 minutes before food.
Patient Education
Thyroid replacement therapy is generally for life. Take in the morning, 30 minutes before breakfast. Do not take antacids or iron preparations within 4 hours of thyroid medication. Report chest pain, rapid heart rate, palpitations, heat intolerance, excessive sweating, increased nervousness, agitation, or lethargy.
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 dosage of thyroid hormone replacement is usually sufficient in elderly patients than in younger adult patients. 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.
Additional Information
Equivalent doses: The following statement on relative potency of thyroid products is included in a joint statement by American Thyroid Association (ATA), American Association of Clinical Endocrinologists (AACE) and The Endocrine Society (TES): For purposes of conversion, levothyroxine sodium (T4) 100 mcg is usually considered equivalent to desiccated thyroid 60 mg, thyroglobulin 60 mg, or liothyronine sodium (T3) 25 mcg. However, these are rough guidelines only and do not obviate the careful re-evaluation of a patient when switching thyroid hormone preparations, including a change from one brand of levothyroxine to another. Joint position statement is available at http://www.thyroid.org/professionals/advocacy/04_12_08_thyroxine.html.
Note: Several medications have effects on thyroid production or conversion. The impact in thyroid replacement has not been specifically evaluated, but patient response should be monitored:
Methimazole: Decreases thyroid hormone secretion, while propylthiouracil decrease thyroid hormone secretion and decreases conversion of T4 to T3.
Beta-adrenergic antagonists: Decrease conversion of T4 to T3 (dose related, propranolol ≥160 mg/day); patients may be clinically euthyroid.
Iodide, iodine-containing radiographic contrast agents may decrease thyroid hormone secretion; may also increase thyroid hormone secretion, especially in patients with Graves' disease.
Other agents reported to impact on thyroid production/conversion include aminoglutethimide, amiodarone, chloral hydrate, diazepam, ethionamide, interferon-alpha, interleukin-2, lithium, lovastatin (case report), glucocorticoids (dose-related), mercaptopurine, sulfonamides, thiazide diuretics, and tolbutamide.
In addition, a number of medications have been noted to cause transient depression in TSH secretion, which may complicate interpretation of monitoring tests for levothyroxine, including corticosteroids, octreotide, and dopamine. Metoclopramide may increase TSH secretion
Anesthesia and Critical Care Concerns/Other Considerations
Clinical Pearls/Comments: Equivalent doses: The following statement on relative potency of thyroid products is included in a joint statement by American Thyroid Association (ATA), American Association of Clinical Endocrinologists (AACE), and The Endocrine Society (TES): For purposes of conversion, levothyroxine sodium (T4) 100 mcg is usually considered equivalent to desiccated thyroid 60 mg, thyroglobulin 60 mg, or liothyronine sodium (T3) 25 mcg. However, these are rough guidelines only and do not obviate the careful re-evaluation of a patient when switching thyroid hormone preparations, including a change from one brand of levothyroxine to another. Joint position statement is available at http://www.thyroid.org/professionals/advocacy/04_12_08_thyroxine.html.
Note: Several medications have effects on thyroid production or conversion. The impact in thyroid replacement has not been specifically evaluated, but patient response should be monitored:
Antithyroid agents: Methimazole decreases thyroid hormone secretion, while propylthiouracil decreases thyroid hormone secretion and conversion of T4 to T3.
Beta-adrenergic antagonists: Decrease conversion of T4 to T3 (dose related, propranolol ≥160 mg/day); patients may be clinically euthyroid.
Iodide, iodine-containing radiographic contrast agents may decrease thyroid hormone secretion; may also increase thyroid hormone secretion, especially in patients with Graves' disease.
Other agents reported to impact on thyroid production/conversion include aminoglutethimide, amiodarone, chloral hydrate, diazepam, ethionamide, interferon-alpha, interleukin-2, lithium, lovastatin (case report), glucocorticoids (dose-related), mercaptopurine, sulfonamides, thiazide diuretics, and tolbutamide.
In addition, a number of medications have been noted to cause transient depression in TSH secretion, which may complicate interpretation of monitoring tests for levothyroxine, including corticosteroids, octreotide, and dopamine. Metoclopramide may increase TSH secretion.
Soy protein may interfere with absorption of levothyroxine sodium. An enteral formula without soy protein should be selected and thyroid function monitored during tube feeding.
Evidence-Based Information: Cadaveric organ donation: Hemodynamically unstable donors: Hormonal resuscitation: Intravenous levothyroxine (20 mcg bolus followed by 10 mcg/hour) given concomitantly with an ampule of 50% dextrose, 2 grams of methylprednisolone sodium succinate, and 20 units of regular insulin has been successfully used in hemodynamically unstable brain-dead donors to increase the quantity and quality of organs available for transplantation (Salim, 2007). Another protocol using liothyronine (T3) has been used with success (Rosendale, 2003; Rosengard, 2002). Stability of levothyroxine solutions (eg, 2 mcg/mL in NS) are stable for at least 12 hours when stored at room temperature and protected from light (Strong, 2010). Stability of further diluted injectable liothyronine solutions has not been adequately studied.
Cardiovascular Considerations
The treatment of patients with combined hypothyroidism and ischemic heart disease needs to be approached very carefully, preferably under the guidance of an endocrinologist and cardiologist. This is because administration of substantial doses of thyroid hormone may precipitate acute cardiac ischemia in patients who have been chronically hypothyroid. Therefore, recognizing that dosing regimens may vary, the general approach is to start at very low doses of thyroid supplementation with very gradual increases in dosage every 3-6 weeks. It is important that patients be monitored very carefully for development of cardiac ischemia during thyroid hormone supplementation. Similarly, patients with heart failure and hypothyroidism should be closely followed.
The possibility of underlying hypothyroidism (and also hyperthyroidism) should be considered in patients with atrial fibrillation. Correction of the underlying thyroid disorder may help in restoration of normal sinus rhythm. Hypothyroidism may also constitute an underlying etiology for obstructive sleep apnea.
Dental Health: Effects on Dental Treatment
No significant effects or complications reported
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No precautions with vasoconstrictor are necessary if patient is well controlled with levothyroxine
Mental Health: Effects on Mental Status
May rarely cause nervousness or insomnia
Mental Health: Effects on Psychiatric Treatment
Used to augment antidepressants; TCAs may increase toxic potential of both drugs
Nursing: Physical Assessment/Monitoring
Use with caution in presence of cardiovascular disease, adrenal insufficiency, and diabetes mellitus. Monitor for hyper-/hypothyroidism on a regular basis during therapy.
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule, soft gelatin, oral, as sodium:
Tirosint®: 13 mcg, 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg
Injection, powder for reconstitution, as sodium: 200 mcg, 500 mcg
Tablet, oral, as sodium: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg
Levothroid®: 25 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg [scored]
Levothroid®: 50 mcg [scored; dye free]
Levoxyl®: 25 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg [scored]
Levoxyl®: 50 mcg [scored; dye free]
Synthroid®: 25 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg [scored]
Synthroid®: 50 mcg [scored; dye free]
Unithroid®: 25 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg [scored]
Unithroid®: 50 mcg [scored; dye free]
Pricing: U.S. (www.drugstore.com)
Tablets (Levothroid)
25 mcg (30): $14.99
50 mcg (30): $14.99
75 mcg (30): $14.99
88 mcg (30): $14.99
112 mcg (30): $15.99
125 mcg (30): $15.99
137 mcg (30): $14.99
150 mcg (30): $15.99
175 mcg (30): $16.99
200 mcg (30): $16.99
300 mcg (30): $20.99
Tablets (Levothyroxine Sodium)
25 mcg (30): $13.99
50 mcg (30): $13.99
75 mcg (30): $14.99
88 mcg (30): $14.99
100 mcg (30): $14.99
112 mcg (30): $15.99
125 mcg (30): $14.99
137 mcg (30): $13.99
150 mcg (30): $14.99
175 mcg (30): $14.99
200 mcg (30): $16.99
300 mcg (30): $19.99
Tablets (Levoxyl)
25 mcg (30): $18.99
50 mcg (30): $19.99
75 mcg (30): $21.99
88 mcg (30): $20.99
100 mcg (30): $19.99
112 mcg (30): $23.99
125 mcg (30): $23.99
137 mcg (30): $23.99
150 mcg (30): $22.99
175 mcg (30): $25.99
Tablets (Synthroid)
25 mcg (30): $24.99
50 mcg (30): $25.99
75 mcg (30): $27.99
88 mcg (30): $28.99
100 mcg (30): $27.99
112 mcg (30): $30.99
125 mcg (30): $30.99
137 mcg (30): $30.99
150 mcg (30): $33.99
175 mcg (30): $35.99
200 mcg (30): $35.99
300 mcg (30): $44.99
Tablets (Unithroid)
25 mcg (30): $16.99
50 mcg (30): $17.99
75 mcg (30): $17.99
88 mcg (30): $18.99
100 mcg (30): $17.99
112 mcg (30): $19.99
125 mcg (30): $19.99
150 mcg (30): $20.99
175 mcg (30): $22.99
200 mcg (30): $25.99
Extemporaneously Prepared
A 25 mcg/mL oral suspension may be made with tablets and 40 mL glycerol. Crush twenty-five 0.1 mg 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.
References
Bauer LA, “Simulations of Levothyroxine Bioavailability Using a Single Dose Protocol,” Am J Ther, 1995, 2:414-6.
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.
Binimelis J, Bassas L, Marruecos L, et al, “Massive Thyroxine Intoxication: Evaluation of Plasma Extraction,” Intensive Care Med, 1987, 13(1):33-8.
Cooper DS, Kloos RT, Mazzaferri EL, et al, “Revised American Thyroid Association Management Guidelines for Patients With Thyroid Nodules and Differentiated Thyroid Cancer,” Thyroid, 2009, 19(11):1167-214.
de Groot JW, Zonnenberg BA, Plukker JT, et al, “Imatinib Induces Hypothyroidism in Patients Receiving Levothyroxine,” Clin Pharmacol Ther, 2005, 78(4):433-8.
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International Brand Names
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