The June 2020 highlighted “VTPP Science in Action” article comes from the laboratory of Dr. Shannon Washburn. The manuscript outlines a series of elegant experiments designed to examine the efficacy of buprenorphine and fentanyl in the management of perioperative pain in sheep. Both agents provided acceptable postoperative analgesia with no adverse effects observed in the ewes or fetuses. The study was highlighted by elegant and transformative data and analyses, including the use of LC-MS for the pharmacologic measurement of buprenorphine and fentanyl concentrations in plasma and amniotic fluid samples as well as validation of a scoring system assessing analgesic indices in sheep.

Figure 3 from the paper shows the mean duration between anesthesia induction and orotracheal intubation between completion of surgery and extubation (dark purple), and between extubation and the animal attaining a standing position (light purple) for the buprenorphine-treated and fentanyl-treated ewes. In all, the recovery and status of the fentanyl-treated ewes is significantly faster than buprenorphine-treatment. The study also demonstrated that the standardized multidimensional pain scores for the ewes were significantly negatively correlated with plasma drug concentrations, demonstrating the pain scoring system used is a reliable method for detecting and assessing pain in sheep.

Perhaps most importantly is the clinical relevance of the studies, where drug availability, costs, and administration logistics are important considerations in perioperative analgesic regimens for veterinary patients. In the United States, buprenorphine (schedule III) and fentanyl (schedule II) are both classified as controlled substances. As such both drugs are viewed as having an abuse potential, which affects their availability. The study reported the cost of the fentanyl protocol ($57.89/ewe) and the buprenorphine protocol ($241.47/ewe). Clinically, fentanyl delivery requires more skin preparation and bandaging materials for transdermal patch application than buprenorphine. However, the animals have to be restrained for analgesic administration only once rather than multiple times, likely favoring use of fentanyl. In any case, the eventual impact of the studies on the use of fentanyl and buprenorphine in the setting of perioperative pain is likely to advance based on these exciting and informative findings. Congratulations again to all the members of the Washburn laboratory on highly impactful work.