Managing pain in cats can be challenging due to medication safety concerns, difficulties in administering medications, and sparse availability of options. Buprenorphine is a partial µ agonist available as a long-acting injectable and has been approved for use in cats (1.8 mg/mL) and as a standard human-labeled injectable solution (0.3 mg/mL); the latter is approved for feline use in some countries but is considered extra-label in the United States.

The effects of buprenorphine are most consistent when the drug is administered via injection (ie, IV, IM [0.3 mg/mL], or SC [1.8 mg/mL]).^1,2 Several studies have demonstrated buprenorphine through the oral transmucosal (OTM) route to be a feasible option, but it is less well absorbed and more variable as compared with injection.^3-5 OTM administration is best used by owners at home or when injection is not practical. Numerous factors (eg, swallowing the drug, salivary pH resulting in drug ionization and lack of absorption, excessive salivation resulting in drug loss or swallowing, spitting out the drug) can affect drug absorption across oral mucous membranes. Most studies assessing OTM drug administration have used cats with healthy oral mucosa. However, inflammation and excessive salivation caused by gingival disease could affect the absorption of OTM buprenorphine.

The purpose of this prospective, randomized, crossover study was to assess the absorption and effects of OTM buprenorphine in cats with gingival disease. Six adult cats with chronic gingivostomatitis received placebo (saline) and buprenorphine (0.02 mg/kg OTM), with a 24-hour washout period between treatments. Pain scores and food consumption (used as part of the total pain score) were measured 30, 90, and 360 minutes after buprenorphine administration. Significant analgesic effects were noted at 30 and 90 minutes but not at 360 minutes. All 6 cats ate 30 minutes after administration of buprenorphine; only 2 ate 30 minutes after administration of saline. Bioavailability was estimated to be 19.5%, which is lower than OTM bioavailability in cats with healthy oral cavities (28.8%). 

Key pearls to put into practice:

Although the authors state that peak drug variability was low, the data show concentrations varying from 274 ng/mL to 1621 ng/mL, approximately a 6-fold range in only 6 cats. The variability in a larger clinical population would be expected to be greater.

Although some of the pharmacokinetic data reported in this paper were inconsistent, this should not affect the clinical applicability of the findings as a whole.

OTM buprenorphine is a feasible short-acting analgesic (<6 hours) for cats with chronic gingivostomatitis, but IV or IM injection is preferred when appropriate.