Optimal dosing of piperacillin-tazobactam for the treatment of Pseudomonas aeruginosa infections:: Prolonged or continuous infusion?

Study Objective. To compare conventional intermittent dosing regimens of piperacillin-tazobactam with prolonged and continuous infusions to determine the optimal dosing scheme against a local Pseudomonas aeruginosa population. Design. Pharmacodynamic Monte Carlo simulation model. Data Source. Microbiologic data from 470 consecutive nonduplicate R aeruginosa isolates collected from a single institution over 6 months in 2006. Patients. Five thousand simulated surgical patients and patients with neutropenia. Measurements and Main Results. We simulated serum concentration-time profiles at steady state for several piperacillin-tazobactam dosing regimens, including intermittent, prolonged, and continuous infusions. The probability of achieving 50% free time above the MIC against 470 P aeruginosa isolates was calculated. The cumulative fractions of response for the intermittent-infusion regimens were 74.7% (3.375 g every 6 hrs), 79.9% (4.5 g every 6 hrs), and 85.6% (3.375 g every 4 hrs). For prolonged-infusion regimens, the cumulative fractions of response were 83.3% (3.375 g every 8 hrs, 4-hr infusion), 87.1% (4.5 g every 8 hrs, 4-hr infusion), and 89.6% (4.5 g every 6 hrs, 3-hr infusion). For continuous-infusion regimens, the cumulative fractions of response were 82.3% (10.125 g), 86.5% (13.5 g), 89.2% (18 g), 90.0% (20.25 g), and 90.6% (22.5 g). Conclusion. Both prolonged- and continuous-infusion strategies improved the pharmacodynamics of piperacillin-tazobactam over those of traditional 30-minute intermittent-infusion regimens. Prolonged- and continuous-infusion regimens that contained the same daily doses of piperacillin had similar likelihoods of bactericidal exposure. Thus, the selection of dosing strategy depends on the availability of intravenous access versus the convenience of once-daily administration.