VANCOMYCIN PHARMACOKINETICS IN MIDDLE-AGED AND ELDERLY MEN

A study was conducted to establish new values for vancomycin volume of distribution (V) and clearance (CL) that would result in more accurate predictions of serum vancomycin concentrations (SVCs). All patients who had received vancomycin at a Veterans Affairs medical center were divided into two groups: those for whom SVCs had been measured between August 13, 1990, and February 12, 1991 (group 1), and those for whom SVCs had been measured between February 13, 1991, and October 4, 1991 (group 2). Data for group 1 were used to derive new values for V and CL by means of Bayesian analysis. SVCs for each patient in group 2 were calculated by using the new pharmacokinetic values, and the predictive performance of these values was compared with that of accepted population values (V = 0.70 L/kg, CL = 0.65 times creatinine clearance [CL(cr)]). Forty-four men with 95 SVCs were entered into group 1, and 69 men with 171 SVCs were entered into group 2. The mean +/- S.D. ages for groups 1 and 2 were 61.6 12.9 and 64.3 +/- 11.3 years, respectively. There were no significant differences between the groups. V could not be evaluated because of inadequate sample size. Compared with the method employing the conventional CL value, the method that assumed a CL of 0.90CL(cr), was more precise and less biased in estimating group 2 SVCs. In middle-aged and elderly men, use of a CL value of 0.90CL(cr) produced estimates of serum vancomycin concentration that were more precise and less biased than did use of a CL value of 0.65CL(cr).