Sulfamethazine residues in swine.

Two possible causes of violative sulfonamide residues in swine were studied. To determine if sulfamethazine accumulated in the tissues of swine when the drug was administered in feed, the rates of plasma drug disappearance following a single oral dose and continuous feeding of the drug were compared. The rate of plasma drug disappearance was not significantly different (alpha = 0.05) when the two methods of drug dosing were compared. When feed containing 2 micrograms sulfamethazine/gm was fed to swine during a 7-day period preceding slaughter, the animal's liver contained violative residues. Violative concentrations of sulfamethazine were detected in the livers, kidneys, and skeletal muscle of swine which consumed feed containing 8 micrograms sulfamethazine/gm.