This study aimed to examine the peritoneal pharmacokinetics of cefepime and to assess its pharmacodynamic exposure in peritoneal fluid (PF). Cefepime (1 g) was administered to eight patients with inflammatory bowel disease before abdominal surgery. Venous blood and PF samples were obtained at the end of the 0.5-h infusion and at 1, 2, 3, 4, 5, and 6 h thereafter. Drug concentrations in plasma and PF were determined, analyzed pharmacokinetically, and used for a Monte Carlo simulation with minimum inhibitory concentration (MIC) data. Cefepime penetrated well into PF, with a maximum drug concentration in a PF/plasma ratio of 0.59 +/- 0.15 (mean +/- SD, n = 8), and an area under the concentration-time curve ratio of 0.90 +/- 0.10. The probabilities of attaining the bacteriostatic and bactericidal targets (40% and 70% of the time above the MIC, respectively) in PF were > or =85% against Escherichia coli, Klebsiella species, and Enterobacter cloacae with 0.5 g every 12 h, 1 g every 12 h, 1 g every 8 h, and 2 g every 12 h. However, 1 g every 8 h or 2 g every 12 h was required for bacteriostatic and bactericidal probabilities > or =85% against Pseudomonas aeruginosa. These conventional regimens did not achieve a high probability against Bacteroides species. These results should help to give us a better understanding of the peritoneal pharmacokinetics of cefepime while also helping to choose the appropriate dosage to prevent surgical intra-abdominal infections on the basis of the pharmacodynamic assessment.