A palliative care patient develops opioid-induced hyperalgesia (OIH). Which statement best characterises OIH and its management?

• A OIH is a paradoxical worsening of pain with increasing opioid doses, mediated by NMDA receptor sensitisation; treatment includes opioid rotation and ketamine ✓
• B OIH is identical to opioid tolerance; increase the opioid dose to restore analgesia
• C OIH occurs only with intrathecal opioids and not with oral or IV routes
• D OIH is treated by abrupt opioid withdrawal to reset central sensitisation

Explanation

Opioid-induced hyperalgesia (OIH) is a paradoxical pain state where prolonged opioid use causes sensitisation of nociceptive pathways, resulting in increased pain sensitivity — pain worsens despite escalating opioid doses, often manifesting as diffuse pain beyond the original site. The mechanism involves NMDA receptor activation, spinal dynorphin release, and descending facilitation pathways. Clinically, it is distinguished from tolerance (which is dose-specific, not location-expanding). Management includes opioid dose reduction or rotation to a different opioid class, NMDA receptor antagonists (ketamine, methadone), and adjuvant therapy. Abrupt withdrawal causes severe withdrawal syndrome and is not appropriate.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.