Comparing 3 methods of monitoring gentamicin concentrations in patients with febrile neutropenia

Abstract

Several nomograms and algorithms have been developed to individualize pharmacokinetic monitoring with their own advantages and disadvantages. This study compared 3 pharmacokinetic methods for predicting doses and monitoring of gentamicin in adult patients with febrile neutropenia. A retrospective study of 75 patients with febrile neutropenia was conducted at the Royal Adelaide Hospital, South Australia. Each patient received a course of once-daily gentamicin and had 2 sets of paired gentamicin serum concentrations. Pharmacokinetic parameters and ensuing doses were compared using 3 pharmacokinetic methods: (1) sequential Bayesian algorithm for gentamicin (SeBA-GEN), (2) Sawchuk-Zaske, and (3) Therapeutic Guidelines: Antibiotic Dose Adjustment Nomogram. The initial median (range) dose of gentamicin administered was 400 (240-640) mg. SeBA-GEN and Sawchuk-Zaske methods recommended similar subsequent gentamicin dose adjustments of 400 (280-640) mg and 400 (280-640) mg, respectively, whereas the Therapeutic Guidelines recommended an increase to 1390 (210-6240) mg. For the Therapeutic Guidelines, 64% of the patients had measured serum gentamicin concentrations that were below the minimum line of the nomogram for the first set of concentrations with only 32% of these patients having an area under the curve value of <70 mg h/L as calculated by SeBA-GEN. The SeBA-GEN method showed a statistically significant increase (68%-77%) in patients attaining the target concentrations of maximum concentration (Cmax) 15-25 mg/L compared with the Sawchuk-Zaske method (72%-65%, P > 0.05). SeBA-GEN also demonstrated greater precision in predicting the area under the curve, Cmax, and minimum concentration (Cmin) compared with the Sawchuk-Zaske method. In conclusion, as the Bayesian approach, that is, SeBA-GEN demonstrated greater precision and more patients were attaining the target concentrations, it is therefore the preferred method for gentamicin monitoring in patients with febrile neutropenia.