55-06-1

white to beige powder

Cytomel,SKF,US,1956

cytochrome P450 inhibitor, Ca antagonist, anesthetic (local)

One of the hormones produced by the thyroid gland that is involved in the maintenance of metabolic homeostasis. Also produced in peripheral tissues as the active metabolite of Thyroxine.

ChEBI: Liothyronine sodium is the sodium salt of liothyronine. Thought to be more active than levothyroxine and with a rapid (few hours) onset and short duration of action, liothyronine sodium is used in the treatment of hypothyroidism, particularly in cases of hypothyroid coma. It contains a 3,3',5-triiodo-L-thyroninate.

Liothyronine sodium (55-06-1) is the sodium salt of the naturally occurring levorotatory isomer of T3. Liothyronine is generally not used for maintenance thyroid hormone replacement therapy because of its short plasma half-life and duration of action. The use of T3alone is recommended only in special situations, such as in the initial therapy of myxedema and myxedema coma and the short-term suppression of TSH in patients undergoing surgery for thyroid cancer. The use of T3 alone may also be useful in patients with the rare condition of 5'-deiodinase deficiency who cannot convert T4 to T3.

The 3,5-diiodo compound used as a starting material is a known material and may be prepared by the method in British Patents 643,089 and 671,070 and in the Journal of the Chemical Society, London, 1949, page 3424.
Synthesis: L-diiodo thyronine (1.05 g) is dissolved in ammonia (specific gravity 0.880) (40 ml) and methanol (40 ml) and iodinated slowly with shaking with N-iodine in KI solution at room temperature. After iodination,most of the ammonia and methanol are removed by evaporation under diminished pressure, water is added to the original volume, the solution is heated to 60°C and brought to pH 4 with hydrochloric acid. A crystalline precipitate is obtained which after cooling to room temperature is collected and washed with water. At this stage, the crude triiodo thyronine is contaminated with thyroxine and a little unchanged diiodo thyronine.
Purification: The crude precipitate is dissolved in boiling 2N HCl (300 ml) and filtered from the relatively insoluble thyroxine hydrochloride. The hot filtrate is brought to pH 4 with 5N NaOH and triiodo thyronine again separates; after chilling at 0° to 4°C it is collected, washed with water and dried. The yield of triiodo thyronine is 70 to 75% of the theoretical. This triiodo thyronine still contains some thyroxine (about 10%).
The final purification consists of chromatographic separation of thyroxine and triiodo thyronine on a kieselguhr column using 20% chloroform in n-butanol equilibrated with 0.5N NaOH as the developing solvent. 80 to 100 mg triiodo thyronine is purified during each run on a 50 g kieselguhr column. Pure Ltriiodo thyronine has MP 236° to 237°C (dec.) and [α]D29.5° = +21.5 in a 4.75% solution in a mixture of 1 part of N HCl and 2 parts of ethanol. Liothyronine is commonly used as the sodium salt.

Thyroid hormone Cytomel (King); Triostat (Jones).

Thyroid hormone

3,3′,5′-Triiodo-L-thyronine (T3) is a thyroid hormone that increases rates of proteins synthesis, stimulates the breakdown of cholesterol, and effects embryonic development. In cell culture, T3 regulates cell differentiation and protein expression. The interaction of T3 with nonhistone proteins in the chromatin initiates the thyroid hormone activity. Thyroid hormones regulate the differentiation and development of tissues and affect a number of metabolic processes. The level of circulating T3 hormone is reduced in hypothyroidism.

Because of its shorter duration of action, liothyronine is generally not considered the drug of first choice in treating hypothyroidism. Infrequently, animals not responding to levothyroxine may respond to liothyronine.

Store at -20°C,protect from light