Generic Cytomel (Liothyronine)

Introduction

Cytomel (liothyronine sodium) is a synthetic form of the thyroid hormone triiodothyronine (T₃). It is supplied as a 20 µg oral tablet and belongs to the class of thyroid hormone replacement agents. The drug restores normal metabolic activity in individuals whose bodies produce insufficient T₃, most commonly due to hypothyroidism or after total thyroidectomy. In addition to its primary role in thyroid hormone replacement, liothyronine is sometimes used off-label for certain mood disorders, refractory hypothyroidism, and as an adjunct in diagnostic testing.

What is Cytomel?

Cytomel is the trade designation for liothyronine sodium, a medication that delivers the biologically active hormone T₃. The product is manufactured by several pharmaceutical companies; the most widely recognized brand name is Cytomel, while other marketed preparations of liothyronine include Thyrolar (a T₄/T₃ combination) and some generic formulations distributed under various national labels. The active compound is liothyronine, a synthetic analogue of the hormone naturally secreted by the thyroid gland.

How Cytomel Works

Liothyronine is identical in structure to endogenous T₃ and binds to nuclear thyroid hormone receptors (TRα and TRβ) in virtually every cell. After oral absorption, peak plasma concentrations occur within 2-3 hours, and the hormone exerts rapid transcriptional effects that increase basal metabolic rate, stimulate protein synthesis, and enhance sympathetic nervous system responsiveness. Because T₃ is the more potent thyroid hormone (≈ 3-4 times more active than thyroxine, T₄), liothyronine can correct hypothyroid states more quickly than levothyroxine alone. The hormone is metabolized primarily by deiodination in the liver and kidneys, with an elimination half-life of roughly 24 hours, allowing once-daily dosing for most indications.

Conditions Treated with Cytomel

• Primary hypothyroidism (especially when rapid normalization of metabolic parameters is required, such as in myxedema coma or severe cardiac disease). Liothyron