Population pharmacokinetic analysis of vancomycin using serum cystatin C as a marker of renal function.

We determined the population pharmacokinetics of vancomycin (VAN) using the glomerular filtration rate (GFR) estimated from the serum cystatin C concentration. We examined the predictive performance of the trough serum VAN concentration for determination of the initial dose by using a new model for the analysis of the population pharmacokinetic parameters. Data for 86 patients were used to estimate the values of the population pharmacokinetic parameters. Analysis with a nonlinear mixed-effects modeling program was done by using a one-compartment model. Data for 78 patients were used to evaluate the predictive performance of the new model for the analysis of population pharmacokinetic parameters. The estimated GFR values determined by using Hoek's formula correlated linearly with VAN clearance (VAN clearance [ml/min]=0.825xGFR). The mean volume of distribution was 0.864 (liters/kg). The interindividual variability of VAN clearance was 19.8%. The accuracy of the prediction determined by use of the new model was statistically better than that determined by use of the Japanese nomogram-based model because the 95% confidence interval (-3.45 to -1.38) of the difference in each value of the mean absolute error (-2.41) did not include 0. Use of the serum cystatin C concentration as a marker of renal function for prediction of serum VAN concentrations may be useful.