Anaes · Intravenous induction agents

Thiopental

Also known as Sodium thiopentone · Thiopentone · Thiobarbiturate · Barbiturate induction agent · Pentothal

Thiopental (sodium thiopentone) is the classic barbiturate induction agent — the first true intravenous induction drug, introduced in 1934 (teaching), now largely replaced by propofol for routine induction (Helmer 2026 German survey of 567 anaesthesiologists: propofol has largely replaced thiopental; sux still the favoured relaxant at 71.7%; GA rate 5 percent). It retains taught niches in obstetric rapid-sequence induction, status epilepticus, and barbiturate-coma neuroprotection — but the modern obstetric evidence base supports propofol as the preferred induction drug with equivalent early neonatal resuscitation and lower maternal accidental-awareness risk (Craig 2026 umbrella review: 7 meta-analyses, 2 systematic reviews, 26 RCTs, 15 observationals; high-risk and emergency cases mostly excluded). It is a taught thiobarbiturate (sulfur at position 2 conferring lipophilicity) acting at the GABA-A receptor by INCREASING the DURATION of chloride channel opening versus benzodiazepine FREQUENCY — barbiturate-class teaching illustrated by the phenobarbital review (Lewis 2024, StatPearls: phenobarbital, not thiopental), with direct opening at high doses (teaching). Taught speed (onset 10 to 30 seconds, recovery 5 to 10 minutes by redistribution) and taught limitation (low extraction, steeply rising context-sensitive half-time, unsuitable for maintenance) are carried honestly — no cited study measured thiopental kinetics. Taught cardiovascular effect (10 to 25 percent BP drop with reflex tachycardia) and pregnancy teaching are carried honestly. Status-epilepticus and neuroprotection citations are scope-limited: a single VNS super-refractory case over 80 days with barbiturate coma as failed background therapy (Parak 2026) and a French sedation survey with 56 percent reporting barbiturate coma for refractory intracranial hypertension amid wide heterogeneity (Ravaux 2026, 115 responses). Allergy framing follows the review rating thiopental below modern agents with xenon safest (Zofia Lisiecka 2026); ketamine-versus-etomidate RSI data show no survival or first-pass difference with more hypotension on ketamine and no thiopental arm (Chilingarashvili 2026, 25 studies); mouse gallic-acid work used thiopental-induced sleep as its model with synergistic diazepam sedation (Yana 2026, mice only). Acute intermittent porphyria (taught ALA-synthase induction) is the absolute taught contraindication; intra-arterial injection of the alkaline solution is the catastrophic taught harm (both teaching, formulary and protocol redirects).