[Methods for studying the hepatic metabolism of drugs in man]

Various methods can be used to investigate human hepatic drug metabolism in vivo. a) Indirect methods based on the assessment of atoxic substances metabolism in order to investigate: --hepatic oxidative activity by antipyrine or caffeine clearance and aminopyrine breath test determination. Such an activity can be modified by drug-induced enzyme induction or inhibition and in case of hepatic disease; --genetic polymorphism of hepatic drug metabolism assessed by the determination of debrisoquine or dextrometorphane metabolic ratio and of N-acetylation phénotype. Unusual therapeutic or adverse effects could be explained by such a polymorphism; --hepatic blood flow, which variations could modify hepatic clearance of drugs with a high hepatic extraction ratio, by the assessment of indocyanine green clearance. b) Direct methods based on pharmacokinetics data and their alterations under various circumstances: simultaneous administration of other drugs, liver disease.