BAYESIAN FORECASTING OF PLASMA VANCOMYCIN CONCENTRATION USING TIME-DEPENDENT PHARMACOKINETICS

A new prediction method of vancomycin (VCM) pharmacokinetics has been developed using the modified Bayesian forecasting method involved in t ime-dependent pharmacokinetics in clearance. We investigated to evalua te the usefulness of this new prediction method compared with that of the ordinary Bayesian forecasting method. Serum samples, obtained from 4 patients at least 3 different days during the period for the VCM tr eatment were assayed by fluorescence polarization immunoassay. VCM pha rmacokinetic parameters and predicted serum VCM concentrations were ca lculated using this new method and the ordinary one according to the o ne-compartment model. The precision of the predicted serum VC-M concen trations by these two methods at the third experimental day were evalu ated with the mean prediction error (ME), mean absolute prediction err or (MAE) and root mean squared error (RMSE). The most precise and leas t-bias prediction of serum VCM concentrations were observed using this new prediction method (ME: -0.36+/-1.40, MAE: 1.13+/-0.82 and RMSE: 1 .37). The time-dependent decrease of VCM clearance was observed in all patients. Therefore, the fitting of the actual serum VCM concentratio ns obtained using the ordinary method produced less precise results th an that using this new method. These results suggest the usefulness of this new prediction method considering time-dependent changes in VCM clearance.