Objective—To characterize the antinociceptive actions of several doses of butorphanol by use of a thermal threshold testing device specifically designed for cats.
Animals—6 domestic shorthair cats.
Procedure—The study was a masked, randomized, crossover design. Thermal thresholds were measured by use of a thermal threshold-testing device specifically developed for cats. A small probe containing a heater element and temperature sensor was held with consistent contact against a shaved area of the cat's skin with an elasticized band. Skin temperature was recorded before each test, prior to activation of the heater. On detection of a response (eg, the cat flinched, turned, or jumped), the stimulus was terminated and the threshold temperature recorded. Three baseline measurements were recorded before IV injection of 0.1, 0.2, 0.4, or 0.8 mg of butorphanol/kg. Each cat received all doses in a randomized order at least 1 week apart. The investigator was unaware of the treatment received. Thermal thresholds were measured every 15 minutes for 6 hours.
Results—Mean ± SD pretreatment threshold temperature for all cats was 40.8 ± 2.2°C. There were no dose-related differences among treatments. There was a significant increase in threshold values for all treatments from 15 to 90 minutes after injection. Mydriasis was detected in all cats after treatment with butorphanol and dysphoric behavior was frequently exhibited.
Conclusions and Clinical Relevance—Results obtained by use of a thermal stimulus indicated that the duration of antinociceptive action of butorphanol was 90 minutes and there was no dose-response relationship in cats. (Am J Vet Res 2004;65:1085–1089)