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) were employed in a single-dose study of orally administered enrofloxacin dosed 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 metabolites was 6.4 +/- 2.0 h with a range of 3-9.4 h. The time of maximal serum concentration (t(max)) occurred at approximately 4 h with a range of 2-8 h following a single oral dose of 5 mg/kg. This variation in t(max) most likely resulted from individual differences in absorption because of variations in the storage and digestion of the fish ration containing the drug dose within the compartmentalized cetacean stomach.