The effectiveness of a long-acting transdermal fentanyl solution compared to buprenorphine for the control of postoperative pain in dogs in a randomized, multicentered clinical study

Linton, D. D., Wilson, M. G., Newbound, G. C., Freise, K. J., Clark, T. P. The effectiveness of a long-acting transdermal fentanyl solution compared to buprenorphine for the control of postoperative pain in dogs in a randomized, multicentered clinical study. J. vet. Pharmacol. Therap.35 (Suppl. 2), 53–64. A prospective, double-blinded, positive-controlled, multicenter, noninferiority clinical study was conducted to evaluate the safety and effectiveness of a long-acting transdermal fentanyl solution (TFS) for the control of postoperative pain. Four hundred forty-five client-owned dogs of various breeds were randomly assigned to receive a single dose of TFS (2.6 mg/kg [∼50 μL/kg]) (N = 223) applied 2–4 h prior to surgery or buprenorphine (20 μg/kg) (N = 222) administered intramuscularly 2–4 h prior to surgery and every 6 h through 90 h. There were 159 (35.7%) males and 286 (64.3%) females ranging from 0.5 to 16 years of age and 3 to 98.5 kg enrolled. Pain was scored using the modified Glasgow Composite Pain Scale with an a priori dropout criteria of ≥8 (20 maximum score). The one-sided upper 95% confidence interval of the mean difference between fentanyl and buprenorphine treatment failures was 5.6%, which was not greater than the a priori selected margin difference of 15%. Adverse events attributed to either treatment were minimal in impact and were approximately equal between groups. Sustained plasma fentanyl concentrations provided by a single pre-emptive dose of TFS are safe and effective and are noninferior to repeated injections of buprenorphine in controlling postoperative pain over 4 days. This long-acting fentanyl formulation provides veterinarians with a novel, registered option for the control of postoperative pain in dogs that improves dosing compliance and potentially mitigates the disadvantages of oral, parenteral, and patch delivered opioids.