The effect of ciprofloxacin on antipyrine metabolism.

The effect of multiple-dose ciprofloxacin on antipyrine metabolism was studied in patients suffering from bacterial infections. The patients were given antipyrine 15 mg/kg intravenously before and after ciprofloxacin treatment. The dosage of ciprofloxacin was 500 mg bd by mouth for 8-10 days. Blood samples were taken at 0, 2, 4, 6, 10 h. Antipyrine total clearance was significantly decreased after ciprofloxacin treatment (0.85 +/- 0.45 vs. 0.52 +/- 0.24 ml/min/kg): elimination rate constants for antipyrine were decreased in all patients after ciprofloxacin, whereas no change in volume of distribution was observed. The average half-life of antipyrine was increased from 9.45 +/- 3.74 h to 14.92 +/- 3.32 h. In two males with advanced chronic hepatic failure the antipyrine half-lives were extremely prolonged. Our results support the hypothesis that ciprofloxacin inhibits intrinsic hepatic drug-metabolizing capacity and may be a source of clinically important drug interactions, particularly in patients with liver disease.