Robert D. Simmons

Pharmacokinetic Studies of Florfenicol in Koi Carp and Threespot Gourami Trichogaster trichopterus after Oral and Intramuscular Treatment

Abstract The pharmacokinetics of florfenicol were studied in koi carp Cyprinus carpio (hereafter, koi) and threespot gourami Trichogaster trichopterus after oral (50 mg/kg) and intramuscular (25 mg/kg) administration of the drug in warm water conditions (24–25°C). The estimates of clearance, volume of distribution, and half-life were 0.05 L · h−1 · kg−1, 1.0 L/kg, and 16 h, respectively, in koi. In threespot gourami, the corresponding estimates were 0.32 L · h−1 · kg−1, 2.0 L/kg, and 4 h. In koi, minimal drug absorption was observed after bath treatment. Analysis of florfenicol leaching from fish feed indicated that about 50–80% of the coated drug is lost and is not available for therapeutic benefit for either species. The minimum inhibitory concentrations of florfenicol, determined for bacterial isolates from tropical fish, ranged from 0.5 to 2 μg/mL. For effective dosing regimens in koi and threespot gourami, the differences in pharmacokinetics should be considered in future studies.

Preliminary Assessment of the Tolerance and Efficacy of Florfenicol against Edwardsiella ictaluri Administered in Feed to Channel Catfish

Abstract A tolerance study was conducted to determine the palatability of florfenicol to channel catfish Ictalurus punctatus. Four tanks of fish (20 fish/tank) were assigned to each of five treatments distinguished by the amount of florfenicol given in feed per kilogram of body weight, namely, 0, 10, 20, 40, or 100 mg. Fish were fed at a rate of 2.5% of body weight per day for 10 consecutive days. On day 11, all surviving fish were euthanatized, counted, and weighed as a group. Florfenicol- medicated feed was palatable to fish at doses of 10, 20, 40, and 100 mg for 10 consecutive days. All 400 fish were necropsied and examined by histopathology, and no treatment-related changes were observed. In a separate exploratory efficacy study, four tanks (20 fish/tank) were assigned to each of the following treatments: (1) not challenged with Edwardsiella ictaluri and fed unmedicated feed, (2) challenged with E. ictaluri and fed unmedicated feed, (3) challenged with E. ictaluri and fed florfenicol at 10 mg per kilo...