Instillation of Vancomycin into a Cerebrospinal Fluid Reservoir to Clear Infection: Pharmacokinetic Considerations

Vancomycin instilled in an Ommaya reservoir was used to treat a reservoir-associated infection. Vancomycin concentrations in cerebrospinal fluid (CSF) were measured, and derivation of pharmacokinetic parameters allowed tailoring of dosing. First-order kinetics were observed. The calculated half-life of 3.52 h was less than reported by others, and the apparent volume of distribution (60 ml) was less than anticipated. The elimination constant was 0.197 h-1. Empiric dosing based on schedules suggested in the literature would have led to high peak and low mean concentrations of intrareservoir vancomycin. Patients with reservoir-associated infections have a variety of pathophysiologic conditions that can result in alteration of normal CSF dynamics. Pharmacokinetic analysis is useful to individualize dosing and to optimize therapy with intrareservoir vancomycin.