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Liothyronine Basics Images Description Formulation Details [Mylan Pharmaceuticals Inc] (5 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (25 mcg) Formulation Details [Mylan Pharmaceuticals Inc] (50 mcg) [Paddock Laboratories Inc] (5 mcg) Formulation Details Formulation Details [Paddock Laboratories Inc] (25 mcg) Formulation Details [Paddock Laboratories Inc] (50 mcg) Formulation Details [X-Gen Pharmaceuticals] (10 mcg/mL) Formulation Details Triostat® [JHP Pharmaceuticals] (10 mcg/mL) Formulation Details Cytomel® [Jones Pharma Inc] (5 mcg) Formulation Details Cytomel® [Jones Pharma Inc] (25 mcg) Formulation Details Cytomel® [Jones Pharma Inc] (50 mcg) Formulation Details Triostat® [Jones Pharma Inc] (10 mcg/mL) Cytomel® [King Pharmaceuticals Inc] (5 mcg) Formulation Details Cytomel® [King Pharmaceuticals Inc] (25 mcg) Formulation Details Images Description Formulation Details Cytomel® [King Pharmaceuticals Inc] (50 mcg) Formulation Details Triostat® [JHP Pharmaceuticals] (10 mcg/mL) U.S. Brand Names Cytomel®; Triostat® Medication Safety Issues Sound-alike/look-alike issues: Liothyronine may be confused with levothyroxine T3 is an error-prone abbreviation (mistaken as acetaminophen and codeine [ie, Tylenol® #3]) Generic Available Yes Pharmacologic Category Thyroid Product Related Terms Liothyronine Sodium; Sodium L-Triiodothyronine; T3 Sodium (error-prone abbreviation) Clinical Pharmacology Mechanism of Action Exact mechanism of action is unknown; however, it is believed the thyroid hormone exerts its many 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 Pharmacokinetics Onset of action: 2-4 hours Peak response: 2-3 days Absorption: Oral: Well absorbed (95% in 4 hours) Half-life elimination: 2.5 days Excretion: Urine Indications & Usage Use Oral: Replacement or supplemental therapy in hypothyroidism; management of nontoxic goiter; a diagnostic aid I.V.: Treatment of myxedema coma/precoma Use: Unlabeled/Investigational Management of hemodynamically unstable potential organ donors increasing the quantity of organs available for transplantation Contraindications Hypersensitivity to liothyronine sodium or any component of the formulation; undocumented or uncorrected adrenal insufficiency; recent myocardial infarction or thyrotoxicosis; artificial rewarming (injection) 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. • 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. Special populations: • Elderly: Use with caution in elderly patients; they may be more likely to have compromised cardiovascular function. Other warnings/precautions: • Monitoring: Thyroid replacement requires periodic assessment of thyroid status. • Weight reduction: [U.S. Boxed Warning]: Thyroid supplements are ineffective and potentially toxic for weight reduction. High doses may produce serious or even life-threatening toxic effects particularly when used with some anorectic drugs. Pregnancy & Lactation Pregnancy Risk Factor A Pregnancy Implications Untreated hypothyroidism may have adverse effects on fetal growth and development, and is associated with higher rate of complications; treatment should not be discontinued during pregnancy. Lactation Enters breast milk (small amounts)/compatible Adverse Reactions 1% to 10%: Cardiovascular: Arrhythmia (6%), tachycardia (3%), cardiopulmonary arrest (2%), hypotension (2%), MI (2%) <1%: Allergic skin reactions, angina, CHF, fever, hypertension, phlebitis, twitching Interactions Drug Interactions 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 Phenytoin: May increase the metabolism of Thyroid Products. Phenytoin may also displace thyroid hormones from protein binding sites. Risk C: Monitor therapy Rifampin: May decrease the serum concentration of Thyroid Products. Risk C: Monitor therapy 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 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 Dosing Dosing: Adults Hypothyroidism: Oral: 25 mcg/day increase by 12.5-25 mcg/day every 1-2 weeks to a maximum of 100 mcg/day; usual maintenance dose: 25-75 mcg/day Patients with cardiovascular disease: Refer to elderly dosing. Suppression test: (T3): Oral: 75-100 mcg/day for 7 days; use lowest dose for elderly Myxedema: Oral: Initial: 5 mcg/day; increase in increments of 5-10 mcg/day every 1-2 weeks. When 25 mcg/day is reached, dosage may be increased at intervals of 5-25 mcg/day every 1-2 weeks. Usual maintenance dose: 50-100 mcg/day. Myxedema coma: I.V.: 25-50 mcg Patients with known or suspected cardiovascular disease: 10-20 mcg Note: Normally, at least 4 hours should be allowed between doses to adequately assess therapeutic response and no more than 12 hours should elapse between doses to avoid fluctuations in hormone levels. Oral therapy should be resumed as soon as the clinical situation has been stabilized and the patient is able to take oral medication. If levothyroxine rather than liothyronine sodium is used in initiating oral therapy, the prescriber should bear in mind that there is a delay of several days in the onset of levothyroxine activity and that I.V. therapy should be discontinued gradually. Simple (nontoxic) goiter: Oral: Initial: 5 mcg/day; increase by 5-10 mcg every 1-2 weeks; after 25 mcg/day is reached, may increase dose by 12.5-25 mcg. Usual maintenance dose: 75 mcg/day. Dosing: Elderly Oral: 5 mcg/day; increase by 5 mcg/day every 2 weeks Dosing: Pediatric Congenital hypothyroidism: Oral: 5 mcg/day increase by 5 mcg every 3-4 days until the desired response is achieved. Usual maintenance dose: 20 mcg/day for infants, 50 mcg/day for children 1-3 years of age, and adult dose for children >3 years. Available Products Excipient information presented when available (limited, particularly for generics); consult specific product labeling. Injection, solution: 10 mcg/mL (1 mL) Triostat®: 10 mcg/mL (1 mL) [contains ethanol 6.8%] Tablet, oral: 5 mcg, 25 mcg, 50 mcg Cytomel®: 5 mcg Cytomel®: 25 mcg, 50 mcg [scored] Administration Administration, Oral When switching to tablets, discontinue the injectable, initiate oral therapy at a low dosage, and increase gradually according to response. Administration, I.V. For I.V. use only; do not administer I.M. or SubQ. Administer doses at least 4 hours, and no more than 12 hours, apart. Resume oral therapy as soon as the clinical situation has been stabilized and the patient is able to take oral medication. If levothyroxine is used for oral therapy, there is a delay of several days in the onset of activity; therefore, discontinue I.V. therapy gradually. Storage & Compatibility Storage Vials must be stored under refrigeration at 2°C to 8°C (36°F to 46°F). Store tablets at 15°C to 30°C (59°F to 86°F). Monitoring Monitoring Parameters T3, TSH, heart rate, blood pressure, renal function, 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. Reference Range Free T3, serum: 250-390 pg/dL; TSH: 0.4 and up to 10 (≥80 years) mIU/L; remains normal in pregnancy Patient Education Inform prescriber of all prescriptions, OTC medications, or herbal products you are taking, and any allergies you have. Do not take any new medication during therapy unless approved by prescriber. Thyroid replacement therapy is generally for life. Take as directed, in the morning before breakfast. Do not take antacids or iron preparations within 8 hours of thyroid medication. Do not discontinue without consulting prescriber. Report chest pain, rapid heart rate, palpitations, excessive sweating or heat intolerance, excessive sweating, increased nervousness, agitation, or lethargy. View the Patient Handout: English | Spanish 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. A synthetic form of L-Triiodothyronine (T3) can be used in patients allergic to products derived from pork or beef. 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 thyroid hormones, including corticosteroids, octreotide, and dopamine. Metoclopramide may increase TSH secretion. References Dahlberg PA, Karlsson FA, and Wide L, “Triiodothyronine Intoxication,” Lancet, 1979, 2(8144):700. Helfand M and Crapo LM, “Monitoring Therapy in Patients Taking Levothyroxine,” Ann Intern Med, 1990, 113(6):450-4. [PMID: 2143640] 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. Rosendale JD, Kauffman HM, McBride MA, et al, “Aggressive Pharmacologic Donor Management Results in More Transplanted Organs,” Transplantation, 2003, 75(4):482-7. [PMID: 12605114] 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. [PMID: 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):405-9. [PMID: 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. [PMID: 2709545] Watts NB, “Use of a Sensitive Thyrotropin Assay for Monitoring Treatment With Levothyroxine,” Arch Intern Med, 1989, 149(2):309-12. [PMID: 2644903] AccessPharmacy © 1978-Present McGraw-Hill and/or its respective owners.