We compared the pharmacokinetics and the serum bactericidal activities of cefpirome, ceftazidime, ceftriaxone, imipenem, and ciprofloxacin. Fifteen healthy volunteers received 1 g of cefpirome, ceftazidime, and ceftriaxone intravenously, 500 mg of imipenem-cilastatin intravenously, and 500 mg of ciprofloxacin orally. High-performance liquid chromatographic assays were used to quantitate unchanged antibiotic in plasma and urine. Serum bactericidal activities were determined against six clinical isolates each of Staphylococcus aureus, Enterobacter cloacae, and Pseudomonas aeruginosa by using a modified microdilution method of Reller and Stratton (L. B. Reller and C. W. Stratton, J. Infect. Dis. 136:196-204, 1977). Overall, cefpirome exhibited pharmacokinetics similar to those of ceftazidime: half-life (t,/2), 1.95 h; concentration at 1 h (Clh), 47 to 49 ig/ml for both antibiotics. Ceftriaxone displayed the longest tV2 (7.65 h) and the highest Clh (137.8 iLg/ml), while we observed the shortest t1/2 (1.05 h) and the lowest Clh (19.85 Fg/ml) with imipenem. At