A 38-year-old man with a 12-year history of heroin dependence presents to the de-addiction clinic seeking treatment. He is motivated for long-term abstinence and wishes to avoid any opioid-like effects. Which medication is the drug of choice for maintenance therapy in this patient?

Explanation

## Maintenance Treatment of Opioid Use Disorder ### Role of Naltrexone in OUD **Key Point:** Naltrexone is a pure opioid antagonist (non-selective) indicated for opioid use disorder in patients seeking complete abstinence and who are highly motivated. **High-Yield:** Naltrexone works by competitive antagonism at all opioid receptors, completely blocking euphoric effects of any opioid use. This makes it ideal for patients who want zero opioid exposure. ### Mechanism and Clinical Advantages 1. **Complete opioid blockade** — prevents reinforcement from any opioid relapse 2. **No abuse potential** — pure antagonist, no intrinsic activity 3. **No withdrawal symptoms** — does not produce physical dependence 4. **Suitable for highly motivated patients** — requires strong commitment since there is no pharmacological "reward" from the medication itself ### Comparison of Maintenance Agents | Agent | Type | Receptor Activity | Abuse Potential | Withdrawal | Best Use Case | |-------|------|-------------------|-----------------|------------|---------------| | **Naltrexone** | Pure antagonist | Blocks all opioid receptors | None | None | Highly motivated, abstinence-focused | | Methadone | Full agonist | Mu-receptor agonist | High (diverted frequently) | Severe | Moderate motivation, harm reduction | | Buprenorphine | Partial agonist | Partial mu-receptor agonist | Lower than methadone | Mild-moderate | Moderate motivation, office-based | | Naloxone | Pure antagonist | Blocks all opioid receptors | None | None | Emergency reversal (not maintenance) | **Clinical Pearl:** Naltrexone requires complete opioid detoxification (7–10 days) before initiation to avoid acute withdrawal. Patients must pass a naloxone challenge test first. ### Why Naltrexone Here? This patient explicitly seeks **long-term abstinence** and wishes to **avoid opioid-like effects**. These are the hallmark indications for naltrexone. His motivation is documented, making him an ideal candidate. **Tip:** Remember the distinction: - **Agonist/partial agonist** (methadone, buprenorphine) → for patients with lower motivation or higher relapse risk (harm reduction) - **Antagonist** (naltrexone) → for highly motivated patients seeking complete abstinence [cite:Harrison 21e Ch 395]