Development and implementation of simplified aminoglycoside empiric dosing guidelines

Poor empiric dosing of aminoglycosides continues to be a problem in many hospitals. Consequently, a two-phase study was undertaken to evaluate gentamicin and tobramycin (G-T) dosing in our institution and to develop practical guidelines to achieve optimum initial G-T serum concentrations. In the pre-intervention phase (phase 1), approximately one-third of 232 G-T treatment courses were initiated with regimens that resulted in low initial serum concentrations. Empiric dosing guidelines were subsequently developed using Pharmacy Pharmacokinetic Service data and literature recommendations. They were validated with patients in phase 1. Compared with earlier dosing methods, the guidelines resulted in initial serum G-T concentrations within the therapeutic range in an equivalent proportion of patients. To simplify the procedure, recommended dosages were based on age, total weight, and serum creatinine only. The guidelines were tabular in format, and prescriber calculations were not required. Pocket and wall chart guidelines were distributed and promoted. During the post-intervention phase (phase 2), the impact of the guidelines was assessed. A review of 232 phase 1 and 203 phase 2 treatment courses revealed an increase in the initial mean dose per interval prescribed after the intervention (p < 0.01). No change in the mean interval was noted. When guidelines were followed, a higher proportion of treatment courses achieved early therapeutic serum concentrations (Cpmax 5-10 mg/L, 80% vs 54%; p < 0.005). The new empiric guidelines appear to be a practical alternative to existing methods of dosing aminoglycosides.