No

Thyroid Product

Replacement or supplemental therapy in hypothyroidism (uniform mixture of T₄:T₃ in 4:1 ratio by weight); little advantage to this product exists and cost is not justified

A

Hypersensitivity to liotrix or any component; recent myocardial infarction or thyrotoxicosis, uncomplicated by hypothyroidism; uncorrected adrenal insufficiency, hypersensitivity to active or extraneous constituents

Ineffective for weight reduction; high doses may produce serious or even life-threatening toxic effects particularly when used with some anorectic drugs; use cautiously in patients with pre-existing cardiovascular disease (angina, CHD), elderly since they may be more likely to have compromised cardiovascular function

<1%: Palpitations, tachycardia, cardiac arrhythmias, chest pain, nervousness, headache, insomnia, fever, ataxia, alopecia, excessive bone loss with overtreatment (excess thyroid replacement), heat intolerance, changes in menstrual cycle, weight loss, increased appetite, diarrhea, abdominal cramps, vomiting, constipation, tremor, myalgia, hand tremors, shortness of breath, diaphoresis

Chronic overdose may cause weight loss, nervousness, sweating, tachycardia, insomnia, heat intolerance, menstrual irregularities, palpitations, psychosis, fever; acute overdose may cause fever, hypoglycemia, CHF, unrecognized adrenal insufficiency

Reduce dose or temporarily discontinue therapy; normal hypothalamic-pituitary-thyroid axis will return to normal in 6-8 weeks; serum T₄ levels do not correlate well with toxicity

In massive acute ingestion, reduce GI absorption, administer general supportive care; treat congestive heart failure with digitalis glycosides; excessive adrenergic activity (tachycardia) require propranolol 1-3 mg I.V. over 10 minutes or 80-160 mg orally/day; fever may be treated with acetaminophen

Decreased effect:

Thyroid hormones increase hypoglycemic drug requirements

Phenytoin clinical lymphothyroidism

Cholestyramine may decrease drug absorption

Increased effect: Increased oral anticoagulant effect

Increased toxicity: Tricyclic antidepressants may increase potential of both drugs

The primary active compound is T₃ (triiodothyronine), which may be converted from T₄ (thyroxine) and then circulates throughout the body to influence growth and maturation of various tissues. Liotrix is uniform mixture of synthetic T₄ and T₃ in 4:1 ratio; 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

Absorption: 50% to 95% from GI tract

Time to peak serum concentration: 12-48 hours

Metabolism: Partially in the liver, kidneys, and intestines

Half-life: 6-7 days

Elimination: Partially in feces and bile as conjugated metabolites

Oral:

Children (dose of T₄ or levothyroxine/day):

0-6 months: 8-10 mcg/kg or 25-50 mcg/day

6-12 months: 6-8 mcg/kg or 50-75 mcg/day

1-5 years: 5-6 mcg/kg or 75-100 mcg/day

6-12 years: 4-5 mcg/kg or 100-150 mcg/day

>12 years: 2-3 mcg/kg or >150 mcg/day

Hypothyroidism (dose of thyroid equivalent):

Adults: 30 mg/day (15 mg/day if cardiovascular impairment), increasing by increments of 15 mg/day at 2- to 3-week intervals to a maximum of 180 mg/day (usual maintenance dose: 60-120 mg/day)

Elderly: Initial: 15 mg, adjust dose at 2- to 4-week intervals by increments of 15 mg

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.

TSH: 0.4-10 (for those greater than or equal to 80 years) mIU/L

T₄: 4-12 mg/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)

Many drugs may have effects on thyroid function tests; para-aminosalicylic acid, aminoglutethimide, amiodarone, barbiturates, carbamazepine, chloral hydrate, clofibrate, colestipol, corticosteroids, danazol, diazepam, estrogens, ethionamide, fluorouracil, I.V. heparin, insulin, lithium, methadone, methimazole, mitotane, nitroprusside, oxyphenbutazone, phenylbutazone, PTU, perphenazine, phenytoin, propranolol, salicylates, sulfonylureas, and thiazides

May cause nervousness or insomnia

None reported

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

No effects or complications reported

Do not change brands without physician's knowledge; report immediately to physician any chest pain, increased pulse, palpitations, heat intolerances, excessive sweating; do not discontinue without notifying your physician; replacement therapy will be for life; take as a single dose before breakfast

Monitor 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

Tablet: 15 mg, 30 mg, 60 mg, 120 mg, 180 mg [thyroid equivalent]

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," Intens Care Med, 1987, 13(1):33-8.

Gorman RL, Chamberlain JM, Rose SR, et al, "Massive Levothyroxine Overdose: High Anxiety - Low Toxicity," Pediatrics, 1988, 82(4):666-9.

Helfand M and Crapo LM, "Monitoring Therapy in Patients Taking Levothyroxine," Ann Intern Med, 1990, 113(6):450-4.

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

Mandel SH, Magnusson AR, Burton BT, et al, "Massive Levothyroxine Ingestion: Conservative Management," Clin Pediatr (Phila), 1989, 28(8):374-6.

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.

Watts NB, "Use of a Sensitive Thyrotropin Assay for Monitoring Treatment With Levothyroxine," Arch Intern Med, 1989, 149(2):309-12.