PHARMACOKINETICS OF NALIDIXIC-ACID IN CULTURED RAINBOW-TROUT AND AMAGO SALMON

The pharmacokinetics and tissue levels of the antibacterial agent, nalidixic acid, were determined after oral administration in cultured rainbow trout and amago salmon. Nalidixic acid levels were determined by a high performance liquid chromatographic method. Serum levels of nalidixic acid were described using a one-compartment pharmacokinetics model. The theoretical time to peak serum concentration of drug (t(max)) was 16.6 h for rainbow trout and 17.6 h for amago salmon, and the concentration at t(max) was 11.4-mu-g/ml and 12.3-mu-g/ml, respectively. Drug absorption was complete in approximately 48 h. The area under the serum concentration-time curve (AUC) and the mean residence time calculated from AUC were similar for the two species. The biological half-life and elimination time in the tissues, with the exception of serum, were shorter in rainbow trout than in amago' salmon. The glucuronic acid conjugate of nalidixic acid was detected in all tissues and in the bile of both species.