| Abstract: | The absorption and disposition kinetics of gentamicin were compared at two dosage levels (2 and 4 mg/kg bodyweight bwt]) in one- and three-month-old foals. Following intramuscular (im) injection of single 2 mg/kg bwt doses, the drug was absorbed rapidly and produced peak serum concentration (18.2 mu 5.3 +/- g/ml, n = 8) at 30 mins. Much wider variations were associated with the amount of drug absorbed and the serum gentamicin concentrations after administration at the higher dosage level. The half-life of gentamicin was similar in the one-month-old (3.7 +/- 1.7 h, n = 8) and three-month-old (3.3 +/- 0.8 h, n = 8) foals, and was independent of the dose. One-month-old foals did not appear to have a deficiency in renal excretion of gentamicin. The minimum inhibitory concentration of gentamicin for Corynebacterium equi and certain other equine bacterial isolates was less than 0.195 microgram/ml. It was concluded that 2 mg/kg bwt administered by im injection at 8 to 12 h intervals, depending on the severity of the infection, could be recommended as the dose rate for treatment of systemic infections caused by microorganisms that are susceptible to gentamicin. |
