PHARMACOKINETIC STUDY OF OXYTETRACYCLINE IN HEALTHY AND VIBRIOSIS-INFECTED AYU (PLECOGLOSSUS-ALTIVELIS)

The pharmacokinetics and bioavailability of oxytetracycline (OTC) were examined in healthy and vibriosis-infected ayu (Plecoglossus altiveli s). Water temperature was maintained at 18.0 +/- 0.3 degrees C in all experiments. Serum concentrations of OTC in healthy fish after intrava scular administration (25 mg kg(-1) body weight) were best described b y a two-compartment model, whereas serum concentration-time curves aft er oral administration (100 mg kg(-1) body weight) in healthy and infe cted ayu could not be fitted by the nonlinear least squares method usi ng one- and two-compartment models with first-order absorption. The es timated bioavailability after oral administration was 9.3% for healthy fish and 3.8% for infected fish. The elimination half-lives of serum, muscle, liver and kidney were 53.1 h, 106 h, 125 h and 117 h for heal thy fish, and 63.2 h, 92.9 h, 107 h and 123 h for infected fish, respe ctively. A significant difference in bioavailability was revealed betw een healthy fish and infected fish, whereas elimination was similar in both fish. Serum protein binding in vivo of OTC was 68.0 +/- 2.8% for healthy fish and 69.9 +/- 4.4% for infected fish.