A 52-year-old man with chronic pain from metastatic cancer is on morphine 60 mg/day. He presents to the emergency department with severe respiratory depression (RR 8/min), pinpoint pupils, and altered mental status. His arterial blood gas shows pH 7.20, PaCO₂ 65 mmHg, PaO₂ 55 mmHg. After securing the airway and initiating mechanical ventilation, which of the following is the most appropriate immediate pharmacological intervention?

Explanation

## Opioid Overdose Management **Key Point:** Naloxone is a competitive opioid antagonist and the gold standard for acute opioid toxicity, regardless of the specific opioid involved. ### Mechanism of Naloxone Naloxone competitively binds to μ, δ, and κ opioid receptors with higher affinity than morphine, rapidly reversing respiratory depression, sedation, and miosis. It has a short half-life (60–90 minutes), necessitating repeated dosing or continuous infusion for long-acting opioids like morphine. ### Dosing Protocol - **Initial dose:** 0.4 mg IV (or IM/IN if IV access unavailable) - **Repeat:** Every 2–3 minutes up to 10 mg total if no response - **Continuous infusion:** 0.4–0.8 mg/hour if opioid is long-acting or overdose is severe **Clinical Pearl:** Naloxone may precipitate acute withdrawal (agitation, tachycardia, hypertension, diaphoresis) but this is preferable to respiratory arrest. The patient's severe respiratory acidosis (pH 7.20, PaCO₂ 65) and hypoxemia demand immediate reversal. ### Why Mechanical Ventilation Is Also Needed While naloxone reverses the opioid effect, mechanical ventilation provides immediate oxygenation and CO₂ elimination while the drug takes effect. Both interventions are essential in severe overdose. **High-Yield:** Naloxone is effective for all opioids (morphine, fentanyl, codeine, heroin, methadone). It has no intrinsic agonist activity and does not depress respiration itself.