How does buprenorphine differ from full mu agonists, and what is a practical implication in cats?

• A. Full mu agonist with strong respiratory depression.
• B. Partial mu agonist with a ceiling effect; provides analgesia with less respiratory depression and can be given transmucosally in cats.
• C. Kappa agonist with no analgesia.
• D. Delta antagonist with no analgesia.

Answer: (B)

Buprenorphine is a partial mu opioid receptor agonist with high receptor affinity and slow dissociation. Because it activates the mu receptor but not to the full extent of a classic opioid agonist, it provides meaningful analgesia while producing a ceiling to respiratory depression. That safety profile is especially valuable in cats, where respiratory risk from strong mu agonists can be a concern. A practical benefit is its suitability for transmucosal administration in cats—the drug can be absorbed well through the oral mucosa, allowing effective analgesia without injections, which is particularly useful for difficult-to-pill patients or at-home care. Analgesia is achieved, but there is less risk of severe respiratory depression compared with full mu agonists, and its high affinity can also influence how other opioids behave if given sequentially.