EFFECTS OF CHRONIC ORAL CIMETIDINE ON APPARENT LIVER BLOOD-FLOW AND HEPATIC MICROSOMAL-ENZYME ACTIVITY IN MAN

Cimetidine 200 mg 3 times daily and 400 mg at night was given to 10 subjects for 4 wk. Apparent liver blood flow was measured by indocyanine green [ICG] clearance and microsomal enzyme activity by antipyrine [AP] clearance, before and after cimetidine. There was no reduction in ICG clearance but AP clearance, as expected, was significantly reduced by 15% at 4 wk. Chronic cimetidine treatment does not reduce apparent liver blood flow and is therefore unlikely to be of use in the treatment of portal hypertension. The cimetidine associated hepatic enzyme inhibition appears to persist with prolonged treatment. Therefore, patients on chronic cimetidine remain vulnerable to certain drug interactions.