Antinociceptive effects of tramadol and acepromazine in cats.

Effects of tramadol and acepromazine on pressure and thermal thresholds were examined in eight cats. After baseline measurements, subcutaneous (SC) tramadol 1 mg/kg, acepromazine 0.1 mg/kg, tramadol 1 mg/kg with acepromazine 0.1 mg/kg, or saline 0.3 ml were given. Serial measurements were made for 24 h. Mean thermal thresholds did not change significantly [analysis of variance (ANOVA)] from baseline. The maximum thermal threshold increase above baseline was 2.8+/-2.8 degrees C at 6 h (P>0.05) after tramadol; it was above the 95% confidence interval (CI) at 0.75, 3 and 6 h. Pressure thresholds increased above baseline from 0.25 to 2 h after acepromazine (P<0.05) and from 0.5 to 3 h after the combination (P<0.05), with a maximum increase of 132+/-156 mmHg 0.25 h after acepromazine and 197+/-129 mmHg 0.5 h after the combination. Pressure thresholds were above the 95% CI from 0.25 to 2 h after acepromazine and from 0.5 to 3 h after the combination. SC tramadol at 1 mg/kg in cats had limited effect on thermal and pressure nociception, but this was enhanced by acepromazine. Acepromazine alone had pressure antinociceptive effects.