Poor bioavailability of oxytetracycline in sharpsnout sea bream Diplodus puntazzo

The pharmacokinetics of oxytetracycline (OTC) were investigated following single intravascular injection (40 mg/kg) in sharpsnout sea bream (90 g) at 19 degreesC. The distribution half-life (t(1/2alpha)) and the elimination half-life (t(1/2beta)) of OTC were calculated to be 1.4 and 35 h, respectively. The apparent volume of distribution of the drug at steady-state (V-d(ss)) was found to be 41/kg. The total clearance rate (CLT) of the drug was low (0.08 1/kg h). Repeated attempts to investigate the bioavailability of OTC following oral administration (75 mg/kg; forced-fed or via the feed), revealed undetectable levels of the drug in plasma and muscle samples. Poor tissue absorption is likely due to significant hepatic metabolism of OTC in sharpsnout sea bream, but this requires further investigation. Thus, oral administration of OTC in fanned sharpsnout sea bream should be discouraged in favour of other routes of administration or other antibiotic drugs. (C) 2003 Elsevier B.V. All rights reserved