Thiopentone

Thiopentone, also known as thiopental or thiopentone sodium, is a short-acting intravenous barbiturate used primarily for the induction of anesthesia and for rapid onset sedation. It is a highly lipophilic drug that rapidly crosses the blood–brain barrier, enabling loss of consciousness within seconds of administration.

Mechanism and pharmacokinetics: Thiopentone potentiates gamma-aminobutyric acid (GABA) activity at the GABA-A receptor, increasing chloride ion influx and producing CNS depression. After IV injection, it is rapidly distributed to the brain and then redistributed to other tissues, with the hypnotic effect lasting only several minutes. It is metabolized in the liver and excreted as metabolites by the kidneys. Onset is typically 30 to 60 seconds, and the duration of hypnosis commonly ranges from 5 to 10 minutes, depending on dose and individual factors.

Clinical use: The drug is used to induce anesthesia and facilitate endotracheal intubation, often as part of rapid sequence induction. It may be followed by other agents to maintain anesthesia. In many settings, thiopentone has been largely replaced by propofol for routine induction, but it remains available in some institutions and regions, particularly where propofol is not accessible or where specific anesthetic plans require a barbiturate.

Adverse effects and precautions: Common risks include apnea or laryngospasm, hypotension and myocardial depression, and irritation at the injection site. It can cause pain upon administration and may produce nausea or vomiting. Porphyria is a contraindication, and caution is advised in patients with significant cardiovascular or respiratory disease, or when combined with other CNS depressants. Long-term use or high doses carry a risk of prolonged sedation and delayed recovery.

Regulatory status: Thiopentone formulations are available in many countries under medical supervision and are subject to controlled-substance regulations.