ABSTRACT— The biliary excretion and pharmacokinetics of mezlocillin have been studied in jaundiced patients with total external bile drainage through a percutaneous transhepatic catheter. In 10 of 11 studies, 2 g mezlocillin intravenously resulted in biliary concentrations sufficient to exceed the minimum inhibitory concentrations of most common biliary pathogenic organisms. In 6 h, 0.2–6.2% of the dose given was recovered in bile. The biliary clearance was 0.21–7.82 ml/min and increased with the duration of biliary decompression. The serum half-life of mezlocillin was prolonged (1.81 ± 0.23 h, mean ± SD), and was due to reduced biliary and renal clearance.