Therapeutic efficacy of cefpiramide and cefoperazone alone and in combination with gentamicin against pseudomonal infections in neutropenic mice

Cefpiramide and cefoperazone alone and in combination with gentamicin were compared for therapeutic efficacy against pseudomonal infections in normal mice and in mice made neutropenic by administration of cyclophosphamide. Neutropenic mice were more susceptible to Infection with Pseudomonas aeruginosa than normal mice. At all challenge doses, combination therapy with either cefpiramide-gentamicin or cefoperazone-gentamicin was more effective than that with a single agent. Therapy with the cefpiramide-gentamicin combination was significantly more active than that with the cefoperazone-gentamicin combination in protecting mice from fatal bacteremia. Pharmacokinetic studies in mice showed that cefpiramide attained a peak serum concentration of 12 micrograms/ml and a serum half-life of 40 min, which are higher than attained by cefoperazone with values of 4 micrograms/ml and 18 min. These factors may have caused the combined cefpiramide-gentamicin therapy to result in significantly improved survival rates in mice as well as in higher bactericidal titers than the cefoperazone-gentamicin combination. The results show that cefpiramide when combined with gentamicin is effective in treating serious infections with P. aeruginosa in neutropenic mice.