COMPARISON OF PORCINE URINE AND BILE AS MATRICES TO SCREEN FOR THE RESIDUES OF 2 SULFONAMIDES USING A SEMIAUTOMATED ENZYME-IMMUNOASSAY

Porcine urine enzyme immunoassays for sulfamethazine and sulfadiazine have previously been employed as screening tests to predict the concen trations of the drugs in the corresponding tissues (kidneys), If a uri ne was found positive (> 800 ng ml(-1)) the corresponding kidney was t hen analysed by an enzyme immunoassay and, if found positive, a confir matory analysis by HPLC was performed. Urine was chosen as the screeni ng matrix since sulfonamides are mainly eliminated through this body f luid, However, after obtaining a number of false positive predictions, an investigation was carried out to assess the possibility of using a n alternative body fluid which would act as a superior indicator of th e presence of sulfonamides in porcine kidney, An initial study indicat ed that serum, plasma and bile could all be used as screening matrices . From these, bile was chosen as the preferred sample matrix and an ex tensive study followed to compare the efficiencies of sulfonamide posi tive bile and urine at predicting sulphonamide positive kidneys, Bile was found to be 17 times more efficient than urine at predicting a sul famethazine positive kidney and 11 times more efficient at predicting a sulfadiazine positive kidney, With this enhanced performance of the initial screening test, the need for the costly and time consuming kid ney enzyme immunoassay, prior to HPLC analysis, was eliminated.