DOI: 10.1577/H03-065.1 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 (here-after, koi) and threespot gourami Trichogaster trichopterus after oral (50 mg/kg) and intramuscular (25 mg/kg) administration of the drug in warm water conditions (24–258C). The estimates of clearance, volume of distribution, and half-life were 0.05 L · h21 · kg21, 1.0 L/kg, and 16 h, re-spectively, in koi. In threespot gourami, the corresponding estimates were 0.32 L · h21 · kg21, 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 mg/mL. For effective dosing regimens in koi and threespot gourami, the differences in pharmacokinetics should be considered in future studies. Ornamental fish are one of the largest groups of pets, and the ornamental aquarium hobby is pur-ported to be the second most popular one in the United States. In 2002 alone, overall fish and fis