Gentamicin Sulfate Pharmacokinetics: Lower Levels of Gentamicin in Blood during Fever

The effect of fever on serum concentrations and urinary excretion of gentamicin sulfate was studied in humans and dogs. Endotoxin-induced fever in dogs resulted in a decrease of approximately 25% in levels of gentamicin in serum 30 and 60 min after intravenous injection of the antibiotic (1.5 mg/kg) when compared with corresponding afebrile values. In six volunteers with etiocholanolone-stimulated fever, serum concentrations of gentamicin was reduced by an average of 40% in all measurements made 1.2, and 3 hr after intramuscular injection (1.5 mg/kg) as compared with afebrile control values in the same subject. Fever was thought to be the principal factor associated with lower levels of gentamicin, although the half-life of gentamicin in serum and renal clearance of the antibiotic were not significantly affected. These findings emphasize the need for frequent measurements of gentamicin in serum as a guide to adjustment of gentamicin treatment in febrile subjects, and perhaps in all patients receiving the antibiotic.