Buprenorphine/naloxone (Suboxone) is the preferred formulation over buprenorphine alone for opioid use disorder treatment. The naloxone component serves which specific pharmacological purpose?

• A Enhances buprenorphine's mu-opioid partial agonism to reduce withdrawal
• B Prevents intravenous misuse — naloxone has poor sublingual bioavailability but precipitates withdrawal if injected ✓
• C Acts synergistically with buprenorphine to block kappa-opioid receptors, reducing dysphoria
• D Prevents constipation by blocking peripheral opioid receptors in the gut

Explanation

Naloxone has very poor sublingual/buccal bioavailability (~3–10%) but high intravenous bioavailability. When Suboxone is taken sublingually as intended, the naloxone is largely inactivated in first-pass hepatic metabolism and exerts minimal systemic effect, so buprenorphine's partial agonist effects dominate. If a patient dissolves the tablet and injects it, naloxone reaches systemic circulation at high concentrations, immediately displacing buprenorphine and any illicit opioids from mu receptors, precipitating acute withdrawal. This 'abuse deterrent' mechanism substantially reduces IV diversion of the combination product.

Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.

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