During intravenous sedation for a patient with a documented history of opioid use disorder, which agent is best avoided?

Correct answer: C. Fentanyl

• A. Nitrous oxide is a reasonable choice, and is often preferred here — rapid onset and offset, minimal abuse liability in a supervised clinical setting, and no opioid receptor activity.
• B. Midazolam is a benzodiazepine with no opioid activity. It carries its own dependence considerations and should be used thoughtfully, but it is not the agent to avoid specifically because of an opioid history.
• C. CORRECT. Fentanyl is a potent µ-opioid agonist, and administering it to a patient in recovery from opioid use disorder risks reactivating craving and precipitating relapse — a genuine and well-documented harm. There is also a pharmacological problem: opioid-tolerant patients require unpredictably higher doses for effect, narrowing the margin between analgesia and respiratory depression. And if the patient is maintained on buprenorphine or naltrexone, fentanyl may be blocked outright or produce an erratic response.
• D. Propofol acts through GABA-A potentiation with no opioid effect and is widely used in this population, though it requires an anaesthesia-trained provider.

Note: Practical approach with a patient in recovery: contact their addiction medicine provider, favour non-opioid analgesia (NSAID plus acetaminophen, long-acting local anaesthetic), use nitrous oxide or a benzodiazepine for anxiolysis, and if opioids become genuinely unavoidable, prescribe a short course with clear documentation and involve their treatment team.