Download Liothyronine Basics

Liothyronine
Basics
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Description
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[Mylan Pharmaceuticals Inc] (5 mcg)
Formulation
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[Mylan Pharmaceuticals Inc] (25 mcg)
Formulation
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[Mylan Pharmaceuticals Inc] (50 mcg)
[Paddock Laboratories Inc] (5 mcg)
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[Paddock Laboratories Inc] (25 mcg)
Formulation
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[Paddock Laboratories Inc] (50 mcg)
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[X-Gen Pharmaceuticals] (10 mcg/mL)
Formulation
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Triostat® [JHP Pharmaceuticals] (10 mcg/mL)
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Cytomel® [Jones Pharma Inc] (5 mcg)
Formulation
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Cytomel® [Jones Pharma Inc] (25 mcg)
Formulation
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Cytomel® [Jones Pharma Inc] (50 mcg)
Formulation
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Triostat® [Jones Pharma Inc] (10 mcg/mL)
Cytomel® [King Pharmaceuticals Inc] (5 mcg)
Formulation
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Cytomel® [King Pharmaceuticals Inc] (25 mcg)
Formulation
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Images
Description
Formulation
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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]
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