Evaluation of Bayesian predictability of vancomycin concentration in patients with various degrees of renal function

To assess the usefulness of the population pharmacokinetic parameters of va ncomycin (VCM) based on a two-compartment model in Japanese adult patients, predictability by a Bayesian method was evaluated using a concentration ti me course after single dosing to 22 patients with various degrees of renal function. Using one or two points from the observed data for each patient, the concentrations predicted by a Bayesian method were compared with the ob served data for each sampling time. The patients were separated into five g roups based on their renal functions indicated by creatinine clearance, and the mean prediction error (MPE) and root mean squared error (RMSE) were ca lculated for each group as measures of accuracy and precision, respectively . In both one- and two-point methods, the absolute MPE values at each sampl ing time in the elimination phase were less than 2.5 mug/ml, and the RMSE v alues were also small. No clear differences were found in MPE and RMSE amon g the groups. In the distribution phase, the MPE and RMSE were somewhat gre ater, and RMSE in some groups was around 15 mug/ml when trough data was use d to predict the peak concentration. Also, the theoretical RMSE using this population parameter setting could well explain the observed RMSE. These re sults confirmed this population parameter setting is useful for at least pr edicting concentration in the elimination phase after single dosing, and th e predictability was independent of renal function.