Liothyronine (T3)

Liothyronine sodium (Cytomel) is a synthetic version of triiodothyronine (T3), the more biologically active thyroid hormone, used as replacement therapy in patients with hypothyroidism. Because of its short half-life and rapid onset, it is sometimes used when a fast therapeutic effect is needed or in combination with levothyroxine (T4) for patients who do not fully respond to T4 alone. Liothyronine should be dosed cautiously in elderly patients and those with cardiovascular disease, as excessive doses can precipitate angina, arrhythmias, or heart failure. Thyroid function should be monitored periodically to guide dose titration.