Objectives: This study aimed to develop a
piperacillin population PK model for
critically ill Brazil-ian patients and describe interethnic variation using an external validation. Methods: Plasma samples were obtained from 24 ICU patients during the fifth day of
piperacillin treatment and assayed by HPLC-UV. Population pharmacokinetic modelling was conducted using Pmetrics. Empiric dose of 4 g IV 6- and 8-hourly were simulated for 50 and 100% fT > MIC and the probabil-ity of target attainment (PTA) and the fractional target attainment (FTA) determined. Results: A two-compartment model was designed to describe the pharmacokinetics of
critically ill Brazillian patients. Clearance and volume of distribution were (mean ± SD) 3.33 ± 1.24 L h−1 and 10.69 ± 4.50 L, respectively.
Creatinine clearance was positively correlated with
piperacillin clearance and a high
creatinine clearance was associated with lower values of PTA and FTA. An external vali-dation was performed using data from two different ethnic ICU populations (
n = 30), resulting in acceptable bias and precision. Conclusion: The primary pharmacokinetic parameters obtained from
critically ill Brazilian patients were similar to those observed in studies performed in
critically ill patients of other ethnicities. Based on our results, the use of dose adjustment based on creati-nine clearance is required in Brazilian patients.