Investigation of the antinociceptive activity of buprenorphine in sheep

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Abstract
1 Buprenorphine given intravenously (6 μg kg−1) was examined for its antinociceptive activity in unrestrained sheep using devices to measure thermal and mechanical thresholds 2 The plasma levels of buprenorphine following intravenous injection over the time period of the antinociceptive testing were measured using a radioimmunoassay. 3 Buprenorphine produced a clear antinociceptive effect lasting for up to three and a half hours when measured by the thermal threshold test, but no detectable antinociception in the mechanical test. 4 The plasma levels of buprenorphine indicated that the drug was rapidly distributed in a manner not dissimilar to that reported in man, although individual animals showed a wide variation in some parameters. 5 When plasma levels of the drug were high (< 700 pg ml−1) during the first sixty minutes, no antinociceptive activity in the thermal test could be detected, which may be due to the slow receptor kinetics shown by this drug.