Buprenorphine has a pharmacologic property that explains its resistance to reversal by naloxone. What is it?

Buprenorphine has a pharmacologic property that explains its resistance to reversal by naloxone. What is it?

• A. Very high affinity for µ receptors
• B. Rapid dissociation from receptors
• C. Low potency
• D. Rapid hepatic metabolism

Answer: (A)

The key idea is receptor binding strength. Buprenorphine binds μ-opioid receptors with very high affinity and dissociates from them very slowly. Naloxone works by competing for those same receptor sites, so when buprenorphine is occupying the receptors tightly, naloxone has difficulty displacing it, especially at typical doses. That’s why reversal can be resistant or require large or repeated naloxone doses. The other options don’t fit this mechanism: rapid dissociation would make reversal easier, not harder; rapid hepatic metabolism affects duration but not the basic receptor binding; and low potency doesn’t explain the strong, persistent receptor occupancy.

The key idea is receptor binding strength. Buprenorphine binds μ-opioid receptors with very high affinity and dissociates from them very slowly. Naloxone works by competing for those same receptor sites, so when buprenorphine is occupying the receptors tightly, naloxone has difficulty displacing it, especially at typical doses. That’s why reversal can be resistant or require large or repeated naloxone doses. The other options don’t fit this mechanism: rapid dissociation would make reversal easier, not harder; rapid hepatic metabolism affects duration but not the basic receptor binding; and low potency doesn’t explain the strong, persistent receptor occupancy.