Liothyronine Sodium
Brand Name: Cytomel, Triostat
Generic Available
Common Dosage Forms:
Tablets (Cytomel): 5 mcg, 25 mcg, 50 mcg
Injection (Triostat): 10 mcg/mL
FDA Indications/Dosages:
For the treatment of mild hypothyroidism: The usual starting oral dose is 25 mcg once daily. May increase at 2 week intervals up to the usual maintenance dose of 25-75 mcg daily.
For the treatment of myxedema: The usual starting oral dose is 5 mcg daily. May increase every 1-2 weeks by 5-10 mcg daily up to the usual maintenance dose of 50-100 mcg daily.
For the treatment of congenital hypothyroidism: Start with 5 mcg orally daily and increase by 5 mcg every 3-4 days until the desired response is achieved.
For the treatment of simple (non-toxic) goiter: Start with 5 mcg orally daily and increase by 5-10 mcg every 1-2 weeks. Normal maintenance dose is 75 mcg daily.
For the treatment of myxedema coma: Start with 25-50 given intravenously (10-20 mcg in known or suspected cardiovascular disease patients). Allow at least 4 hours but not more than 12 hours between subsequent doses up to a maximum of 100 mcg daily.
Monitor: TSH, Serum T4, INR
Pharmacology/Pharmacokinetics: The human thyroid gland produces two thyroid hormones, T4 (levothyroxine) and T3 (liothyronine). The difference between the two forms is the number of iodine atoms each contains. T4 contains 4 iodine atoms and T3 contains 3 iodine atoms. The mechanism by which thyroid hormones act in the body are not well understood. It is known they increase the metabolic rate, they increase the metabolism of carbohydrates, lipids, and proteins, and they increase the use of oxygen in tissues throughout the body. Liothyronine is extensively absorbed orally with a rapid onset of action. Maximum effects are seen after a few days of continuous dosing. T3 has a lower affinity for binding to the thyroid-binding globulin and thyroid-binding prealbumin than does T4.
Drug Interactions: May increase the effects of anticoagulants when thyroid therapy is started. Cholestyramine impairs absorption of liothyronine if given within 4-5 hours of an oral dose. Estrogens decrease free thyroxine in patients without a functioning thyroid gland. May increase the effects of tricyclic antidepressants, digitalis, and vasopressors. Use with ketamine may cause hypertension.
Contraindications/Precautions: Contraindicated in patients with diagnosed and uncorrected adrenal cortical insufficiency, untreated thyrotoxicosis, and in patients hypersensitive to any ingredient. Do not use for the treatment of obesity as the risk outweighs any benefit. Use with caution in patients with cardiovascular disease. Thyroid therapy increases the intensity of the symptoms of diabetes mellitus or insipidus or adrenal cortical insufficiency and treatment of these diseases in patients should be monitored closely when starting, stopping, or changing thyroid doses. Pregnancy Category A.
Adverse Effects: Adverse effects are indicative of high doses and include headache, irritability, nervousness, sweating, arrhythmia, increased bowel motility, and menstrual irregularities.
Patient Consultation:
May be taken without regard to food or meals.
If a dose is missed, skip it and return to normal dosing schedule. Do not double doses.
Contact a physician if the above side effects are pronounced or persistent.
Successful therapy is determined by compliance. Every effort should be made to not skip or miss doses.
