EFFICACY OF INTRA-MUSCULAR ANALGESICS FOR ACUTE PAIN IN SHEEP

The analgesic action of intramuscularly injected buprenorphine, methad one, flunixin meglumine and xylazine was examined in sheep, using alge simetry based on a leg withdrawal response to an electrical stimulus. No analgesic response was detected for buprenorphine, methadone or flu nixin meglumine, Only the alpha 2-adrenoceptor agonist, xylazine, prod uced an analgesic response. The current required to elicit a response increased by 170% (4.5 +/- 0.43 mA to 12.23 +/- 1.14 mA; mean +/- SE) after a dose of 0.05 mg/kg xylazine; by 180% (4.73 +/- 0.3 mA to 13.28 +/- 2.35 mA) after 0.1 mg/kg; and by 510% (4.52 +/- 0.29 mA to 27.63 +/- 3.89 mA) after 0.2 mg/kg. Intramuscular xylazine appears to be an effective analgesic agent for acute pain in the sheep and further inve stigation into ideal administration regimens and dosage may provide mo re detailed information on relationships between dose, analgesic and s edative effects. The findings also suggest that some common analgesic agents, and opioids in particular, may be ineffective for the manageme nt of acute pain in sheep and that any analgesic should be administere d only on the basis of its proven efficacy in that species.