Bioavailability, pharmacokinetics, and analgesic activity of ketamine in humans.
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 at plasma ketamine concentrations above 160 ng/ml.
D000284:Administration, Oral; D000328:Adult; D000700:Analgesics; D001682:Biological Availability; D006801:Humans; D007273:Injections, Intramuscular; D007275:Injections, Intravenous; D007649:Ketamine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D007700:Kinetics; D010146:Pain / Q000517:prevention & control; D005082:Physical Exertion
D000700:Analgesics; D007649:Ketamine