Enrofloxacin serum bioactivity in bottlenose dolphins, Tursiops truncatus,following oral administration of 5 mg/kg in whole fish

Eight adult bottlenose dolphins Tursiops truncatus (six male, two female) w ere employed in a single-dose study of orally administered enrofloxacin dos ed at 5 mg/kg body weight. Blood samples were obtained from all animals at 0, 2, 4, 8, 12 and 24 h following administration of the dose in the animals morning ration of fish, Serum antimicrobial activity concentrations (SAAC) were determined using bioassay. The mean elimination half-life (t(1/2)) of enrofloxacin and its major metab olites was 6.4+/-2.0 h with a range of 3-9.4 h. The time of maximal serum c oncentration (t(max)) occurred at approximately 4 h with a range of 2-8 h f ollowing a single oral dose of 5 mg/kg, This variation in t(max) most likel y resulted from individual differences in absorption because of variations in the storage and digestion of the fish ration containing the drug dose wi thin the compartmentalized cetacean stomach.