Thermal antinociception following oral administration of tapentadol in conscious cats

Objective To evaluate the onset, magnitude and duration of thermal antinociception after oral administration of two doses of tapentadol in cats. Study design Prospective, randomized, blinded, experimental study. Animals Six healthy adult cats weighing 4.4 +/- 0.4 kg. Methods Skin temperature (ST) and thermal threshold (TT) were evaluated using a wireless TT device up to 12 hours after treatment. Treatments included placebo (PBO, 50 mg dextrose anhydrase orally), buprenorphine (BUP, 0.02 mg kg(-1)) administered intramuscularly, low-dose tapentadol (LowTAP, 25 mg orally; mean 5.7 mg kg(-1)) and high-dose tapentadol (HighTAP, 50mg orally; mean 11.4 mg kg(-1)) in a blinded crossover design with 7 day intervals. Statistical analysis was performed using ANOVA with appropriate post hoc test (p <= 0.05). Results Salivation was observed immediately following 11 out of 12 treatments with tapentadol. The ST was significantly increased at various time points in the opioid treatments. Hyperthermia (>= 39.5 degrees C) was not observed. Baseline TT was 45.4 +/- 1.4 degrees C for all treatments. Maximum TT values were 48.8 +/- 4.8 degrees C at 1 hour in LowTAP, 48.5 +/- 3.0 degrees C at 2 hours in HighTAP and 50.2 +/- 5.3 degrees C at 1 hour in BUP. TT significantly increased after LowTAP at 1 hour, after HighTAP at 1-2 hours, and after BUP at 1-2 hours compared with baseline values. TTs were significantly increased in BUP at 1-2 hours compared with PBO. Conclusion and clinical relevance Oral administration of tapentadol increased ST and TT in cats. The durations of thermal antinociception were similar between HighTAP and BUP, both of which were twice as long as that in LowTAP. Studies of different formulations may be necessary before tapentadol can be accepted into feline practice.