Biphasic kinetic profile for carbamazepine epoxide formation.

The formation of the stable 10,11-epoxide from carbamazepine by rat liver microsomes was studied. A biphasic activity-substrate profile was consistently found with microsomes from both control and phenobarbital pretreated rats. These data could either indicate epoxide formation by multiple catalytic sites with differential substrate affinity or a solvent effect on the enzyme or its environment.