Bactericidal activity of low-dose ceftizoxime plus metronidazole compared with cefoxitin and ampicillin-sulbactam

Eighteen volunteers received ceftizoxime 1 g plus metronidazole 500 mg intravenously every 12 hours, cefoxitin 2 g intravenously every 6 hours, and ampicillin-sulbactam 3 g every 6 hours in a triple-crossover, open-label study to compare serum bactericidal titers (SBTs) against two strains of Escherichia coli and Bacteroides fragilis. Serum was analyzed for drug concentration and bactericidal activity. Ceftizoxime-metronidazole exhibited a significantly greater (p < 0.05) area under the bactericidal curve and percentage of the dosing interval with SBTs of 1:2 or above against E. coli than cefoxitin or ampicillin-sulbactam. The respective values were equal to those of ampicillin-sulbactam for one strain of B. fragilis (both greater than cefoxitin) and greater than cefoxitin and ampicillin-sulbactam for the other strain. A 1-g dose of ceftizoxime given with metronidazole 500 mg every 12 hours should be an effective alternative to standard antibiotic treatment of mixed aerobic-anaerobic bacterial infections.