Piperacillin-tazobactam pharmacokinetics in patients with intraabdominal infections.

STUDY OBJECTIVE

To determine the appropriate compartmental and noncompartmental pharmacokinetic parameters for intravenous piperacillin and tazobactam.

DESIGN

Sequential selection of patients entered into a randomized, open-label clinical efficacy trial.

SETTING

Los Angeles County-University of Southern California Medical Center.

PARTICIPANTS

Sequential sample of 18 patients admitted for intraabdominal infections and consented into a comparative antibiotic trial.

INTERVENTIONS

Patients received piperacillin 4 g plus tazobactam 500 mg by intravenous intermittent infusion every 8 hours.

MEASUREMENTS AND MAIN RESULTS

The estimated noncompartmental pharmacokinetic parameters (mean +/- SD) for piperacillin and tazobactam, respectively, were as follows: maximum concentration in plasma 218.7 +/- 48.9 micrograms/ml and 27.8 +/- 9.1 micrograms/ml; half-life 1.07 +/- 0.22 hours and 1.00 +/- 0.27 hours; elimination rate constant 0.67 +/- 0.13 hr-1 and 0.73 +/- 0.18 hr-1; area under the concentration-time curve from zero hour to infinity 288.5 +/- 71.25 mg.hr/L and 36.3 +/- 9.55 mg.hr/L; total plasma clearance 14.75 +/- 3.93 L/hour and 14.78 +/- 4.39 L/hour; renal clearance 5.69 +/- 1.94 L/hour and 7.85 +/- 3.37 L/hour; volume of distribution at steady state 21.00 +/- 4.18 L and 22.47 +/- 8.27 L; and mean residence time 1.72 +/- 0.29 hours and 1.79 +/- 0.35 hours.

CONCLUSION

Our findings were similar to those in other surgical patient models. The two-compartmental model best described piperacillin and tazobactam disposition in our patients. Bayesian analyses of the two-compartment models of piperacillin and tazobactam were able to predict trough, peak, and 2-hour postadministration levels without bias.