The pharmacokinetics of ketamine in analgesic doses after intravenous, intramuscular, and oral administration was investigated in healthy volunteers. Plasma ketamine concentration-time curves were fitted by a two-compartment open model with a terminal half-life of 186 min. Absorption after intramuscular injection was rapid and the bioavailability was 93%. However, only 17% of an oral dose was absorbed because of extensive first-pass metabolism. Simultaneous measurements of the elevation of pain threshold in an ischemic exercise test showed a marked effect for 15-60 min after intramuscular injection, but little or no effect after the oral solution. Pain threshold elevation occurred a t plasma ketamine concentrations above 160 nglml.
Keyphrases 0 Ketamine-bioavailability, pharmacokinetics, and analgesic activity in humans, intravenous, intramuscular, and oral administration compared Pharmacokinetics-ketamine, intravenous, intramuscular, and oral dosage forms compared Anesthetics-ketamine, bioavailability, pharmacokinetics, and analgesic activity in humans Ketamine [2-o-chlorophenyl-2-(methylamino)cyclohexanone] is an anesthetic induction agent which produces sleep rapidly after intravenous injection of 1-2 mg/kg (1).