A Radioactive Tracer Study to Determine the Excretion and Persistance of Drug Residues in Sows and Piglets Following the Induction of Parturition with 3H PGF2α
Butine, Tala J.
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PGF2α has been shown to be effective in inducing parturition in late-term sows and has much promise as a useful product for commercial swine operations. However, the use of any drug in animals intended for human consumption creates concern about potentially harmful concentrations of drug residues in edible tissues. Studies examining the residues in PGF2α-treated animals other than pigs have revealed a pattern of absorption and excretion with an early peak, fairly rapid decline, and little persistence of residues in tissues after 48 hours. However, almost no work has been done with PGF2α residues in swine to date. This paper is concerned with a radioactive tracer study done at the Upjohn Company that investigated drug residue levels in four sows that had parturition induced with tritium(3H)-labeled PGF2α. Since drug transfer to the piglets of PGF2α-treated sows is possible by means of placental blood exchange or ingestion of the sows' milk, concentrations of PGF2α residues in the piglets were also determined. Piglet tissues were collected immediately following birth, and 48 and 72 hours post-injection. Sow tissues were collected 72 hours post-injection. It was found that PGF2α was rapidly absorbed by the sow as indicated by the occurrence of peak blood residue levels 20 minutes after injection. PGF2α and its metabolites were quickly excreted in urine and feces resulting in no detectable levels of radioactivity in the edible tissues except low levels found in one liver and some of the injection site samples. Some of the tissues from piglets sacrificed at birth and 48 hours post-injection had detectable concentrations of radioactivity, but none of the tissues from piglets sacrificed at 72 hours had detectable residues. The source of residues in the piglets could not be determined from this study. It was concluded that unacceptably persistent drug residues in edible tissues from sows and their piglets will not be a major hurdle in the approval of Prostaglandin F2α for use in parturition induction in swine.