OBJECTIVE

Doripenem is a valuable broad-spectrum antibiotic for empirical therapy in critically ill patients, although little data exist to guide effective dosing. We sought to describe the population pharmacokinetics of doripenem in critically ill patients with nosocomial pneumonia and then to use Monte Carlo dosing simulations to procure clinically relevant dosing recommendations for that population.

DESIGN

Pharmacokinetic analysis of Phase III Trial data.

SETTING

Critical care units at multiple centers.

PATIENTS

Thirty-one critically ill adult patients with nosocomial pneumonia.

INTERVENTIONS

Serial blood samples were taken on day 2 or 3 of treatment and used for population pharmacokinetic analysis with nonlinear mixed effects modelling and Monte Carlo simulation.

MEASUREMENTS AND MAIN RESULTS

A two-compartment linear model was most appropriate. The mean values for doripenem clearance (20.4 ± 14.2 L/hr) and volume of distribution (45.9 ± 36.3 L) were larger than that observed in previous studies in noncritically ill patients. Doripenem clearance was correlated with creatinine clearance and peripheral volume of distribution with patient body weight. Administration by extended infusion negated much of the pharmacokinetic variability caused by different patient body weight and renal function and enabled achievement of concentrations associated with maximal bacterial killing.

CONCLUSION

: This is the first article describing the pharmacokinetics/pharmacodynamics of doripenem solely in critically ill patients and emphasizes the effect of patient weight and creatinine clearance on pharmacokinetics. Use of extended infusions with this antibiotic should be encouraged as it maximizes the likelihood of achieving target blood concentrations.