Study Objective. To compare the efficacy of constant-infusion ceftazidime (CTZ) with that of traditional intermittent dosing in a pilot trial.

Design. Prospective, crossover trial.

Subjects. Five adults with cystic fibrosis requiring intravenous antibiotic therapy for pulmonary exacerbations of the disease.

Interventions. Patients were initially treated with standard CTZ 2 g 3 times/day for 10 days. At the next hospitalization patients were crossed over and CTZ was administered as a constant infusion at a rate determined to achieve a serum concentration 6.6 times the minimum inhibitory concentration (MIC) of the least susceptible Pseudomonas aeruginosa isolate.

Measurements and Main Results. The pharmacokinetics of CTZ were determined, as were MICs for all P. aeruginosa isolates. Outcome parameters of interest were changes with therapy in white blood cell count, P. aeruginosa density in sputum, and pulmonary function test results. Differences in these parameters for the two forms of administration were not significant. With the exception of one patient who received 6 g/day with both regimens, the average reduction in dosage with the constant infusion was 50%.

Conclusion. These preliminary data suggest that constant-infusion CTZ may be as safe and efficacious as intermittent dosing.