Depletion of penicillin G residues in sows after intramuscular injection

A penicillin G procaine residue depletion study was conducted in heavy sows to estimate the pre-slaughter withdrawal periods necessary to clear penicillin from kidney and muscle. Heavy sows (n=126) were treated with penicillin G procaine at a 5x dose (33,000 IU/kg) for 3 consecutive days by intramuscular (IM) injection using 3 separate patterns of drug administration. Treatments differed by pattern and volume of penicillin G procaine administration. Sets of 6 animals per treatment were each slaughtered with 5, 10, 15, 20, 25, 32, and 39 day withdrawal periods; skeletal muscle and kidney were collected for penicillin G analysis by LC-MS/MS. Penicillin residues in skeletal muscle averaged 23.5 ± 10.5 ng/g at withdrawal day 5 for all treatments, but averaged 3,760 ± 1,930 ppb in kidney