Pharmacokinetics of florfenicol and behaviour of its metabolite florfenicol amine in orange-spotted grouper (Epinephelus coioides) after oral administration

Pharmacokinetics and elimination of florfenicol and florfenicol amine in grouper held in sea water at 23.3 +/- 0.8 degrees C were studied using HPLC method after they were given a single peroral dose of florfenicol at 24mgkg(-1) body weight. Florfenicol was rapidly absorbed from intestine and distributed extensively to all the tissues examined. The maximum concentrations (C-max, gg(-1) or gmL(-1)) in plasma and tissues were observed at 2-6h (the time to reach maximum concentration, T-max) except for bile (T-max=24h) and were in the order of intestine (52.02 +/- 25.07)>bile (49.41 +/- 28.16)>gill (45.12 +/- 11.10)>plasma (28.28 +/- 5.43)>liver (21.97 +/- 12.08)>muscle (21.63 +/- 6.12)>kidney (20.88 +/- 11.28)>skin (19.10 +/- 5.88). The drug distribution level was higher in plasma than in extravascular tissues except for bile, based on the ratios of the area under concentration-time curve between tissue and plasma (AUC(tissue/plasma)). The elimination of florfenicol was rapid in fish, and the corresponding half-lives (T-1/2) in the order of magnitude were bile (13.92h)>muscle or liver (12.31h)>skin (11.77h)>plasma (11.57)>gill (11.04h)> intestine (10.55h)>kidney (10.05h). The delayed T-max, lower C-max and longer T-1/2 for florfenicol amine compared with florfenicol were measured in grouper.