Therapeutic Use of Gentamicin in Horses: Concentrations in Serum, Urine, and Synovial Fluid and Evaluation of Renal Function

Abstract

Serum, synovial fluid, and urine concentrations of gentamicin were measured in normal mature horses which had been given a single dose of the drug. Mean peak serum concentration (16.8 microgram/ml) occurred in horses 30 minutes after they were given a single intramuscular dose of 4.4 mg of gentamicin/kg of body weight. In horses given a smaller dose of gentamicin (1.7 mg/kg), mean peak serum concentrations of gentamicin (10.2 microgram/ml) appeared at 1 hour. Synovial fluid concentration was maximum at 2 hours for both doses; in horses given the larger dose, mean peak concentration was 6.4 microgram/ml, and in those given the smaller dose (1.7 mg/kg), 3.4 microgram/ml. Measurable concentrations of gentamicin in serum and synovial fluid persisted 8 hours. During the first 8 hours, percentages of gentamicin excreted in the urine were between 3.9 and 32.8% of the larger dose and between 3.3 and 13.4% of the smaller dose. Serum creatinine concentrations were serially measured in 10 hospitalized horses intramuscularly given 1.7 to 4.4 mg of gentamicin/kg 4 times a day' significant increase in creatinine concentration was not found.