PLASMA CONCENTRATIONS AND DISPOSITION KINETICS OF ENROFLOXACIN IN GOPHER TORTOISES (GOPHERUS POLYPHEMUS)

Twelve adult gopher tortoises (Gopherus polyphemus) were randomly allotted into two groups. Six tortoises received a single i.m. injection of enrofloxacin at a dose of 5 mg/kg body weight. Blood samples were collected via a jugular catheter, and plasma concentrations of enro floxacin were measured at 1, 3, 6, 12, 24, 48, 72, and 96 hr postinjection. The highest mean concentration of 2.43 Mg/ml was measured at 1 hr postinjection; thereafter, the mean plasma con centration decreased to <0.2 ??g/ml by 96 hr. The apparent terminal half-life was calculated to be 23.1 hr. A second group of tortoises received i.m. injections of enrofloxacin at 5 mg/kg body weight every 24 hr for five treatments. Blood was collected immediately before each injection and at 1 hr after each injection. Over the 5-day period of sampling, there was a stepwise increase in mean trough and peak plasma concentrations of enrofloxacin. In addition to the kinetics study, the minimum inhibitory concentrations of enrofloxacin for 17 Pasteurella testudinis isolates from the nasal cavity of tortoises were measured. Based upon the results of this study, enrofloxacin should be administered at 5 mg/kg body weight every 24-48 hr to maintain enrofloxacin concentrations above the MIC of P. testudinis.