DISTRIBUTION AND ELIMINATION OF OXOLINIC ACID IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS WALBAUM) AFTER A SINGLE RAPID INTRAVASCULAR INJECTION

Pharmacokinetic studies are important tools in improving the dosage regimens for antibiotics currently in use. In this study elimination half-life, apparent volume of distribution and total clearance of oxolinic acid (OA) were estimated after a single intravascular injection of OA in rainbow trout kept in freshwater and in seawater at 8.5-degrees-C. The drug was given as a rapid injection through a cannula into the dorsal aorta. Repeated blood samples were taken via the cannula and serum was analysed by reversed-phase high-performance liquid chromatography. The terminal elimination half-life for OA in rainbow trout was estimated to be 52.6 h in freshwater (t1/2,beta) and 29.1 h in seawater (t1/2,tau). This considerable difference in elimination half-lives was mainly due to the increase in total clearance; total clearance (Cl(T)) values were 1.2 and 2.0 1 kg-1 24 h-1. The apparent volume of distribution (V(d)(ss)) was estimated to be 2.9 and 2.6 1 kg-1 in freshwater and seawater, respectively.