Thiopental Sodium

Thiopental sodium , the sodium salt of 5-ethyl-5-(1-methylbutyl)thiobarbituric acid, a yellowish-white, crystalline, slightly bitter powder, is very soluble in water and soluble in alcohol. The compound is hygroscopic and has a weak unpleasant odor. The free acid forms colorless crystals, mp 158 – 159 ?C.A10%solution of the sodium salt has a pH of 10.6.

Yellowish-white, hygroscopic powder.

Pentothal (Abbott).

A rapidly acting barbiturate administered intravenously for general anesthesia and hypnosis. Commonly known as “truth serum.”

Thiopental is BAN.

May cause respiratory failure; use onlywith physician in attendance.

Thiopental is highly bound to albumin, and free drug availability is increased in hypoproteinaemia. Protein binding is decreased by alkalaemia, hyperventilation and some drugs that occupy the same albumin binding sites, thereby increasing unbound thiopental concentrations. Metabolism occurs predominantly in the liver, and the metabolites are excreted by the kidneys. Only a small proportion is excreted unchanged in the urine. The terminal elimination half-life is approximately 11.5h (longer in the elderly). Elimination after an infusion is a zero-order process with 10%–15% of the remaining drug metabolised each hour. Up to 30% of the original dose may remain in the body at 24h, and a hangover effect is common. Accumulation may result if further doses of thiopental are administered within 1–2 days.

Thiopental sodium is a short-acting intravenous anesthetic used for brief surgical procedures and induction of anesthesia. It is a potent,rapidly effective hypnotic. Sleep ensues within 30 – 60 s. A disadvantage is the lengthy hangover. In the United States and Great Britain it is the most widely used injection anesthetic. Abuse can lead to addiction.

Poison by ingestion, intraperitoneal, rectal, subcutaneous, and intravenous routes. Human systemic effects by intraarterial route: acute arterial occlusion; by rectal route: respiratory depression, body temperature decrease, general anesthetic. An experimental teratogen. Experimental reproductive effects. An intravenous anesthetic. When heated to decomposition it emits toxic fumes of NO, and Na2O. See also PENTOTHAL and BARBITURATES

Because of its rapid action and short duration, in young, healthy animals, thiopental is excellent induction agent (rapid IV bolus) for general anesthesia with other anesthetics or as the sole anesthetic agent for very short procedures. In sick or debilitated animals, thiopental may be used in a more cautious manner (IV, slowly to effect).