Correlation of aminoglycoside and vancomycin pharmacokinetic parameters

To investigate a correlation between the elimination rate constants (Ke) of aminoglycosides (AG) and vancomycin; to investigate the correlation between actual Ke and creatinine clearance (Clcr) for AG versus vancomycin; to investigate the calculated versus actual Ke for AG and vancomycin; and to investigate a correlation between volumes of distribution (Vd) between AG and vancomycin.

Retrospective data collection.

Patients in our institution who received AGs or vancomycin concomitantly or within six weeks of each other were identified retrospectively. Patient subpopulations were identified and analyzed collectively as well as individually. Steady-state serum concentrations of AG and vancomycin (more than four half-lives) were obtained and kinetic parameters (Ke, Vd) were calculated using first-order pharmacokinetic equations. Linear regression was used to determine correlation coefficients.

In the total population and all subpopulations, the correlation between Ke of AG and vancomycin was superior to the correlation between Ke and Clcr. The correlations (r2) between Ke for AG and vancomycin in the total, general medicine, oncology, and intensive care units (ICU) populations were 0.572, 0.878, 0.349, and 0.561, respectively. The correlations (r2) between Ke and Clcr for AG in the total, general medicine, oncology, and ICU populations were 0.235, 0.430, 0.005, and 0.238, respectively. The correlations (r2) between Ke and Clcr for vancomycin in the total, general medicine, oncology, and ICU populations were 0.300, 0.407, 0.055, and 0.309, respectively.

The correlation between Ke of AG and vancomycin may be beneficial for predicting Ke of vancomycin when AG concentrations have already been obtained or vice versa, and may give more accurate estimations of dosing intervals and require less time adjusting, ordering, and interpreting concentrations and dosages.