SummaryThe effects of age, gender, and body weight on the pharmacokinetics of vancomycin were examined using data collected as part of routine therapeutic drug monitoring in patients. One thousand eighty-five sets of steady-state peak and trough serum concentrations obtained from 704 different patients were used to calculate elimination rate constant (k), volume of distribution (V), and clearance (Cl) using a one-compartment model. The median half-life of vancomycin was 6.5 h. Clearance was significantly correlated with creatinine clearance as estimated using the Cockcroft-Gault equation Cl = 0.771 (Clcr) plus; 18.9; r = 0.63. V averaged 0.69 L/kg ideal body weight (IBW) with increased values in females, patients over age 60, and obese patients. V ranged from 0.58 L/kg IBW in normal weight males under age 40 to 1.17 L/kg IBW in obese females over age 60. V was not different in underweight patients and those of normal weight (43.8 vs. 44.4 L). Regression analysis indicated that V was more predictable in women than in men and that vancomycin distributed into excess body weight (EBW) to a greater extent in women. However, the correlation coefficients from multiple regression analysis of V with IBW, EBW, and age did not exceed 0.60, and the high root mean square error values of 11ndash;15 L suggest considerable variability in V is not accounted for by these factors alone. Despite these limitations, dosing of vancomycin may be improved by adjusting initial estimates of V for patient age, gender, and obesity.
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