Transfer of ciprofloxacin to bile and determination of biliary metabolites in humans.

1-Cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-piperazin-1-ylquinol ine-3-carboxylic acid (ciprofloxacin, Bay o 9867; designated tradename: Ciprobay) is a new synthetic pyridone-carboxylic acid antimicrobial agent for oral use which has high activity against gram-positive and gram-negative bacteria and anaerobes. In 8 patients with T-tube drainage, the biliary excretion of ciprofloxacin and its metabolites including the glucuronide were determined by bioassay and HPLC. After single oral administration of ciprofloxacin 400 mg in 5 patients, the biliary excretion of the drug was investigated for 12 h. The peak biliary concentration of ciprofloxacin was 15.0 +/- 6.3 micrograms/ml by bioassay and 11.0 +/- 4.0 micrograms/ml by HPLC. The biliary concentration of the drug was 10 times as high as its serum concentration, indicating a good biliary excretion. The proportion of ciprofloxacin glucuronide in the biliary excretion, calculated from the difference between the concentration before beta-glucuronidase hydrolysis and that after the hydrolysis, was 30%. In 3 patients, biliary metabolites of ciprofloxacin were investigated. Main metabolites were the sulfone compound (Bay s 9435) and the oxo compound (Bay q 3542) and, in addition, a minor metabolite was detected.