Influence of xenobiotics on drug metabolism and its sensitive detection.

Biotransformation of drugs and other xenobiotics in the liver plays an important role intoxication and detoxication processes, i.e. changes in biotransformation activity have significant biological consequences. For that reason the determination of biotransformation activity is useful. The rate of some biotransformation reactions can be markedly changed by very small doses of xenobiotics. These changes may be used for the sensitive detection of the exposure to xenobiotics. Among biotransformation reactions cytochrome P-450-dependent monooxygenation is very important. It can be induced and inhibited by xenobiotics. Induction of P-450 forms can be detected by various methods, e.g. by using model reactions. Ethoxycoumarin O-deethylation, ethoxyresorufin O-deethylation, pentoxyresorufin O-depentylation and ethylmorphine N-demethylation are catalyzed at different P-450 forms, and their determination is described in detail.