|Newman, David - North Dakota State University|
|Larsen, Steven - National Pork Board|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2013
Publication Date: 9/9/2013
Citation: Smith, D.J., Lupton, S.J., Shelver, W.L., Newman, D.J., Larsen, S. 2013. Depletion of penicillin G residues in sows after intramuscular injection. Meeting Abstract. SafePork 2013 Proceedings Book. 2013. p. 39.
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 40 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.
Technical Abstract: The US-FDA CVM has not established a tolerance for penicillin residues in swine tissues, but across much of Europe and Asia a tolerance of 50 ppb penicillin G is in effect. In the US, heavy sows are often treated with extra-label doses of penicillin G, however appropriate pre-slaughter withdrawal periods (WP) are not well defined. Heavy sows (n=126) were treated with a 5x dose (33,000 IU/kg) of penicillin G procaine by intramuscular (IM) injection for 3 consecutive days using 3 separate patterns of injection. Sets of 6 animals per administration pattern were each slaughtered at 5, 10, 15, 20, 25, 32, and 39 days after the last IM injection; skeletal muscle, kidney, serum, and urine were collected for penicillin G analysis by LC-MS/MS. Residue concentrations among animals and tissues were highly variable. No discernible effects of injection pattern on penicillin G residues were noted. Penicillin residues in skeletal muscle, kidney, serum and urine averaged 23.5 +/- 10.5, 3,760 +/- 1,930, 440 +/- 141, and 332,000 +/- 320,000 ppb, respectively, at withdrawal day (WD) 5. By WD 15, skeletal muscle residues were quantifiable in a single sow (3.4 ppb) but residues averaged 119 +/- 199 ppb in kidneys. Using a tolerance of 50 ppb and a ln-linear depletion model, the WP required for penicillin depletion in skeletal muscle was 11 days, whereas a 47 day WP was required for kidney. The FARAD recommended WP of 15 days for hogs treated with extra-label doses (66,000 IU/kg) of penicillin is adequate for skeletal muscle, but is inadequate for kidney. Slaughter of penicillin treated hogs after a 15-day WP with edible offal discard would ensure the safety of skeletal muscle of sows treated with penicillin G procaine in an off-label manner.