The biotransformation kinetics of ketamine "in vitro" in rabbit liver and lung microsome fractions.

The biotransformation kinetics of Ketamine in 10,000 g supernatant fractions of liver and lung homogenates was studied. The products found in the incubation mixtures by gas chromatography and mass spectrometry were identified. In the two homogenates studied it was only possible to detect and identify metabolite I of ketamine. This study enabled us to characterize the kinetic parameters in order to define the biotransformation of ketamine (Km and Vmax) in the two organs studied. The lung enzyme systems were found to be more easily saturable than those of the liver. Furthermore, the fact that all of the ketamine is biotransformed and only 60% of metabolite norketamine appears suggests the existence of parallel biotransformation pathways for this anaesthetic.