Which of the following opioids has the shortest duration of action and is preferred for acute postoperative pain management due to its rapid onset and offset?

Explanation

## Opioid Pharmacokinetics in Acute Pain Management **Key Point:** Remifentanil is an ultra-short-acting synthetic opioid with a duration of action of 3–5 minutes, making it ideal for acute perioperative pain and intraoperative analgesia. ### Mechanism of Rapid Offset Remifentanil is rapidly metabolized by non-specific plasma and tissue esterases, independent of hepatic or renal function. This ester hydrolysis results in: - Onset: 1–2 minutes - Peak effect: 2–3 minutes - Duration: 3–5 minutes (context-insensitive) - Rapid recovery even after prolonged infusion ### Comparison of Common Opioids | Opioid | Onset (min) | Duration (min) | Metabolism | Clinical Use | |--------|-------------|----------------|------------|---------------| | Remifentanil | 1–2 | 3–5 | Plasma esterase | Intraoperative analgesia, acute postop pain | | Morphine | 5–10 | 180–240 | Hepatic glucuronidation | Moderate-to-severe acute pain | | Methadone | 30–60 | 360–720 | Hepatic (CYP3A4) | Chronic pain, opioid maintenance | | Buprenorphine | 15–30 | 360–720 | Hepatic (CYP3A4) | Chronic pain, partial agonist properties | **High-Yield:** Remifentanil's context-insensitive half-life (t½ = 17–19 min) means its duration does NOT increase with prolonged infusion, unlike other opioids. This makes it the gold standard for acute postoperative analgesia in recovery settings. **Clinical Pearl:** Remifentanil is often combined with longer-acting opioids (e.g., morphine) at the end of surgery to prevent acute postoperative pain rebound after remifentanil discontinuation. **Warning:** Remifentanil causes rapid respiratory depression and should never be used as a sole agent for acute ward pain management — it requires continuous monitoring and IV access.