PENICILLIN RESIDUES IN TREATED CHINOOK SALMON

Muscle tissue concentrations of penicillin-G (pen-G) were measured in different groups of Chinook salmon on different days using an HPLC ass ay. Following oral administration of antimicrobial by gastric lavage f or 10 days, measurable concentrations declined rapidly from a range of 0.05-10.58 mug/gm of muscle tissue on the first day following drug re moval to concentrations ranging from 0.1 to 0.6 mug/gm on the seventh and ninth days post drug removal. Pen-G tissue residues could not be d etected in all fish. After drug administration by intraperitoneal inje ction, measurable tissue concentrations were considerably higher and r anged from 0.37 to 42 mug/gm on the first day after withdrawal, but fe ll to concentrations of 0.07-0.92 mug/gm by the tenth day. Considerabl e variability in muscle pen-G concentrations was observed in all fish on each day of sampling, thus indicating that monitoring strategies fo r pen-G residues in salmon must take into account considerable inter-f ish differences in tissue levels.