ABSTRACT
Variability in drug response represents an important issue in drug development and therapy (Lin and Lu, 1997). Because of the inter individual variability in dose/plasma concentration/response (therapeutic and/or toxic effects) relationships, patients might need different dosage regimens. Much of this variability is caused by the significant inter individual variation in oxidative drug metabolism, resulting mostly from variability in the activity of different cytochrome P450 (CYP) enzymes in the liver and extrahepatic tissues. The sources of variability are genetic and environmental factors (including drugs and food constituents/diets), as well as age and various disease states (Vesell, 1991; Murray 1992; Turner et a l., 1992; Wilkinson, 1997; Rodighiero, 1999).
