Dexamethasone does not alter in vitro antibacterial efficacy of gentamicin.

Abstract

Aminoglycoside ototoxicity may be mitigated by administration of dexamethasone; however, dexamethasone could theoretically impair its antibacterial properties. The purpose of this experiment was to determine if dexamethasone decreases the antibacterial activity of gentamicin against Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA). In vitro microbiological assay. Four separate trials of minimum inhibitory concentration (MIC) testing were performed for gentamicin against five PA strains and six SA strains, with and without the addition of high and low concentrations of dexamethasone. MICs were not changed by more than one dilution with the addition of either high or low concentrations of dexamethasone for any of the PA and SA strains. Dexamethasone does not impair the antibacterial efficacy of gentamicin for PA and SA. This supports the role of dexamethasone as an oto-protectant with aminoglycoside therapy.