Cytomel Side Effects

Generic name: liothyronine

Note: This document contains side effect information about liothyronine. Some of the dosage forms listed on this page may not apply to the brand name Cytomel.

Some side effects of Cytomel may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to liothyronine: oral tablet

Get emergency medical help if you have any of these signs of an allergic reaction while taking liothyronine (the active ingredient contained in Cytomel) hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Less serious side effects may include temporary hair loss (especially in children).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to liothyronine: compounding powder, intravenous solution, oral tablet

General

Liothyronine is generally well tolerated. Side effects associated with liothyronine (the active ingredient contained in Cytomel) therapy typically result from therapeutic overdosage and include manifestations of hyperthyroidism such as weight loss, increased appetite, diarrhea or increased bowel frequency, insomnia, nervousness, irritability, tremor, excessive sweating, heat intolerance, palpitations, hypertension, tachycardia, chest pain, and menstrual irregularities.

Cardiovascular

Cardiac function was evaluated in twenty patients requiring TSH suppression for either thyroid goiter or following thyroidectomy and radioactive iodine therapy for thyroid cancer and in twenty age- and sex-matched controls. TSH suppression was associated with an increased incidence of premature ventricular beats, an increased left ventricular mass index, and enhanced left ventricular systolic function. The clinical significance of these changes remains to be determined.

Cardiovascular side effects of thyroid hormone therapy have included palpitations, hypertension, tachycardia, and angina, all of which may be exacerbated in patients with underlying cardiovascular disorders. In the treatment of myxedema coma/precoma, cardiovascular side effects associated with the use of intravenous liothyronine have included arrhythmia (6%), tachycardia (3%), cardiopulmonary arrest (2%), hypotension (2%), and myocardial infarction (2%). Angina, congestive heart failure, hypertension, and phlebitis have occurred in approximately 1% or fewer of patients.

Endocrine

Endocrine side effects of thyroid hormone therapy have included changes in symptom presentation for diabetes and adrenal cortical insufficiency. Treatment measures of these conditions may require adjustment.

Nervous system

Nervous system side effects of thyroid hormone therapy have rarely included seizures during initiation of therapy. In the treatment of myxedema coma/precoma, twitching has been reported in approximately 1% or fewer of patients treated with intravenous liothyronine (the active ingredient contained in Cytomel)

Dermatologic

Dermatologic side effects of thyroid hormone therapy have included transient hair loss during the initial months of therapy. Rarely, allergic skin reactions have been reported with liothyronine (the active ingredient contained in Cytomel)

Musculoskeletal

Musculoskeletal side effects of thyroid hormone therapy have included an increased risk of osteoporosis. However, data from long-term studies are conflicting.

A study evaluated the effect of long-term thyroid hormone therapy on bone mineral density in 196 women (mean age, 74.4 years) compared to a control group comprised of 795 women (mean age, 72.1 years). The mean daily thyroxine dose was 1.99 mcg/kg (range, 0.3 to 6.6 mcg/kg) and the mean duration of therapy was 20.4 years (range, less than 1 to 68 years). Women taking daily doses of 1.6 mcg/kg or more had significantly lower bone mineral density levels at the ultradistal radius, midshaft radius, hip, and lumbar spine compared to controls. However, estrogen use appeared to negate the adverse effects of thyroid hormone on bone mineral density.

Higher rates of femur fractures have been found in males (p=0.008) prescribed long-term thyroid hormone therapy as compared to controls in a case-control analysis of 23,183 patients from the United Kingdom General Practice Research Database.

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