[Biotransformation in liver damage]

Xenobiotics may produce liver damages. Vice versa primary liver diseases influence metabolism and elimination of drugs. The activity of the isoenzymes of the monooxygenase system which catalyze biotransformation reactions in the liver can be tested by model substances (Cyt P-450Pb: Metamizol, Cyt P-450MC: Caffeine, Cyt P-450db1: Debrisoquine). It can be influenced by estrogens, gestagens, smoking, alcohol. Only severe stages of liver diseases reduce the biotransformation of drugs. Thus in liver cirrhosis the excretion of unchanged furosemide is increased. The bioavailability of propranolol is changed by a reduced first pass effect in liver cirrhosis. In patients with drug hepatitis after dihydralazine 15 out of 17 patients are genetically slow acetylators and they show also a lower activity of phase I cytochrom P-450 catalyzed biotransformation reactions. The same holds true for patients with haemochromatosis. Determination of the 7-ethoxycoumarin-O-deethylase (ECOD) in liver biopsy samples allows the correlation of the decrease in biotransformation with the increase of liver cell necrosis, intraacinous fibrosis and structural changes. Possibly the changes in biotransformation caused by liver diseases are connected with a disturbed regeneration of the liver corresponding to the concept of the "streaming liver".