Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2014
Publication Date: 7/8/2014
Publication URL: http://handle.nal.usda.gov/10113/59452
Citation: Lupton, S.J., Shelver, W.L., Newman, D.J., Larsen, S., Smith, D.J. 2014. Depletion of penicillin G residues in heavy sows after intramuscular injection. Part I: Tissue residue depletion. Journal of Agricultural and Food Chemistry. 62(30):7577-7585. Interpretive Summary: Pencillin G procaine is an antibiotic that is often used at very large doses to prevent infection in injured or sick sows that are nearing the end of their productive lives. Although the antibiotic was approved several decades ago for use hogs, it was approved for use in market hogs at modest doses, not for use in very large sows. Nevertheless, the off-label use of penicillin G procaine is allowed under the auspices of the Animal Drug Use Clarification Act as long as an adequate pre-slaughter withdrawal period is observed. This study was conducted to determine what an adequate withdrawal period is for heavy sows treated with penicillin G procaine. We learned that the proper pre-slaughter withdrawal period is greater than 50 days if kidneys are used as the tissue of interest. However, residues in skeletal muscle are completely depleted 15 days after the administration of penicillin. Therefore we are recommending that sows treated with penicillin G procaine be slaughtered 15 days after their last treatment day and that kidneys not be used for human food in treated animals. It is unknown whether regulatory agencies will agree with this recommendation.
Technical Abstract: Heavy sows (n=126) were treated with penicillin G procaine at a 5x label dose (33,000 IU/kg) for 3 consecutive days by intramuscular (IM) injection using 3 separate patterns (treatments) of drug administration (42 sows per treatment). Treatments differed by pattern and maximum injection volume per site of penicillin G procaine administration. Sets of 6 animals per treatment were each slaughtered 5, 10, 15, 20, 25, 32, and 39 days after the last treatment; skeletal muscle, kidney, serum, liver, and urine were collected for penicillin G analysis by quantitative LC-MS/MS. Penicillin residues at withdrawal day 5 averaged 23.5 ± 10.5 and 3,762 ± 1,932 ppb in skeletal muscle and kidney, respectively. After 15 days of withdrawal, skeletal muscle penicillin G residues were quantifiable in only one treated hog (3.4 ppb) but averaged 119 ± 199 ppb (mean includes 8 non-detects counted at ½ the limit of detection) in kidneys of the same swine. Using a hypothetical tolerance of 50 ppb and a natural log-linear depletion model, the withdrawal period required for penicillin depletion to 50 ppb was 11 days for skeletal muscle and 47 days for kidney. A withdrawal period of 15 days for hogs treated with extra-label doses of penicillin is adequate for residue depletion from skeletal muscle, but is inadequate for kidney. Slaughter of penicillin treated hogs after a 15 day withdrawal period, with kidney discard would ensure the human food safety of skeletal muscle from hogs treated with extra-label doses penicillin G procaine.