Experimental methods for pharmacokinetic studies in salmonids

Many aspects of the use of chemical agents to combat diseases in aquaculture should be based on a firm knowledge of their pharmacokinetic behaviour in fish. The environmental conditions (temperature, salinity, pH etc.) under which kinetic studies are conducted, may vary greatly. Pharmacokinetic experiments to determine the rate and magnitude of absorption from water or feed, distribution, qualitative and quantitative metabolism and excretion in fish under various environmental conditions, are important for the determination of correct dosage regimens and withdrawal periods. These studies are often technically very difficult to carry out. Several techniques and experimental designs for different kinetic experiments are described in this review. Techniques requiring considerable manipulation of the fish, such as anaesthesia, catheterisation, cannulation, and immobilisation in metabolism chambers, will subject the fish to significant stress, which in turn may influence the data generated. The parameters reported thus often show considerable divergence. The influence of the experimental design on the results obtained has rarely been studied or addressed in papers describing pharmacokinetic studies in fish. In future studies, more attention should be paid to validation of the experimental methods.