A 35-year-old man with a history of tuberculosis is found unconscious with a respiratory rate of 6 breaths per minute and pinpoint pupils. He is suspected to have taken an overdose of morphine. Which is the drug of choice for immediate reversal of opioid toxicity?

Explanation

## Management of Opioid Overdose **Key Point:** Naloxone is the drug of choice for acute opioid overdose because it is a **pure opioid antagonist** with rapid onset and short duration, making it ideal for emergency reversal of life-threatening respiratory depression. ### Mechanism of Opioid Overdose Excessive opioid binding to mu receptors in the brainstem causes: - Severe respiratory depression (life-threatening) - Miosis (pinpoint pupils) - Loss of consciousness - Potential cardiovascular collapse ### Pharmacology of Naloxone | Feature | Naloxone | Naltrexone | Buprenorphine | Methadone | |---------|----------|-----------|---------------|----------| | **Receptor action** | Pure antagonist | Pure antagonist | Partial agonist | Full agonist | | **Onset** | 2–3 minutes (IV) | 30 minutes (oral) | Hours | Hours | | **Duration** | 30–90 minutes | 24–72 hours | Long (24–72 hrs) | Long (24–36 hrs) | | **Use in overdose** | YES — immediate reversal | No — too slow | No — agonist activity | No — agonist activity | | **Withdrawal risk** | High (abrupt reversal) | High | Low | Low | **High-Yield:** Naloxone's **short duration (30–90 min)** means the patient may relapse into respiratory depression as naloxone wears off — **continuous monitoring and repeat dosing** are essential. ### Clinical Management Algorithm ```mermaid flowchart TD A[Opioid Overdose: Respiratory Depression + Miosis]:::outcome --> B[Naloxone 0.4-2 mg IV]:::action B --> C{Response in 2-3 min?}:::decision C -->|Yes: Respiratory rate improves| D[Observe continuously]:::action C -->|No| E[Repeat naloxone every 2-3 min]:::action D --> F{Relapse into depression?}:::decision F -->|Yes| G[Repeat naloxone or infusion]:::action F -->|No| H[Discharge with counseling]:::outcome E --> I[Maximum 10 mg total]:::action I --> J{Still unresponsive?}:::decision J -->|Yes| K[Consider non-opioid cause]:::outcome ``` **Clinical Pearl:** Naloxone precipitates acute withdrawal (agitation, tachycardia, hypertension, body aches) in opioid-dependent patients, but this is preferable to death from respiratory arrest. Titrate slowly if possible. **Tip:** Always give naloxone IV in emergency settings; IM/intranasal routes are slower. Prepare for potential violent agitation post-reversal. [cite:Harrison 21e Ch 474]