title: Etomidate as a rectal induction agent. Part I. A preliminary study in rats.
abstract: Etomidate (Hypnomidate; Janssen) 1,25% in sterile water was given rectally on 100 occasions to 50 male Long-Evans rats in doses ranging from 4 mg/kg to 12 mg/kg. The onset and duration of ataxia and hypnosis (i.e. loss of righting ability) were recorded. Ataxia was observed in all rats, even at the lowest dose levels. The lowest hypnotic dose was 6 mg/kg, when 2 out of 5 rats lost their righting ability. In all 50 rats given 8 mg/kg or more hypnosis occurred within 4 minutes (range 2-4 minutes, average 3,3 minutes), from which they recovered within an average of 10,4 minutes. The duration of hypnosis and time to full recovery from ataxia were dose-dependent. The rectal hypnotic dose of etomidate in rats has been found to be approximately ten times the documented intravenous dose. No mortality was recorded despite the rectal administration of ten times the intravenous lethal dose (LD50) for rats. Histological examination of the rectal and colonic mucosa showed that etomidate 1,25% in sterile water (pH 3,5) caused no significant mucosal change, but undiluted etomidate 12,5% (pH 1,8) caused haemorrhagic necrosis. We conclude that rectal etomidate 1,25% in sterile water is an efficient, predictable, evanescent and safe method of inducing anaesthesia in rats and warrants further investigation in clinical anaesthesia in children.
mesh_terms: D000774:Anesthesia, Rectal; D000818:Animals; D003106:Colon / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004341:Drug Evaluation; D005045:Etomidate / Q000008:administration & dosage*; D007093:Imidazoles / Q000008:administration & dosage*; D008297:Male; D009092:Mucous Membrane / Q000473:pathology; D051381:Rats; D012007:Rectum / Q000473:pathology; D013997:Time Factors
chemical_list: D007093:Imidazoles; D005045:Etomidate