Effect of probenecid on the excretion of ampicillin in human bile.

1. Ampicillin concentrations were determined in serum and bile after intravenous injection into patients with T-tube bile drainage of 1 gram ampicillin before and during probenecid medication. The concentrations were followed up to fifteen hours after injection.2. Probenecid increased the half-life of ampicillin in serum from 74 minutes to 137 minutes.3. Ampicillin concentrations in bile were higher following probenecid medication and a concentration over 5 mug/ml was obtained for 3 h longer than before probenecid.4. The ampicillin concentrations in bile were approximately the same as those in serum both before and during probenecid medication suggesting passive transport of ampicillin from blood to bile.5. A combined treatment of ampicillin and probenecid might be of clinical value in the therapy of cholangitis and typhoid carriers.