Opioid-induced hyperalgesia

Opioid-induced hyperalgesia (OIH) is a medical condition characterized by an increased sensitivity to pain resulting from the prolonged use of opioids. This phenomenon is distinct from tolerance, where the effect of a drug diminishes over time, and physical dependence, where withdrawal symptoms occur when a drug is abruptly discontinued.

Etiology

The exact cause of OIH is not fully understood. However, it is believed to be related to the long-term exposure of the nervous system to opioids, which can alter the functioning of pain pathways and increase sensitivity to painful stimuli. This can result in a paradoxical response where the individual experiences increased pain despite increasing doses of opioids.

Clinical Presentation

Patients with OIH often present with a diffuse, non-localizable, and fluctuating pain pattern that is out of proportion to the identified pathology. The pain often extends beyond the original pain site and can be accompanied by abnormal pain behaviors and a decreased functional status.

Diagnosis

Diagnosis of OIH can be challenging due to its overlap with other conditions such as tolerance and opioid withdrawal. A high index of suspicion is required, especially in patients who have escalating opioid requirements without a clear cause.

Treatment

Treatment strategies for OIH include reducing or discontinuing the opioid, rotating to a different opioid, or adding a non-opioid analgesic. In some cases, NMDA receptor antagonists such as ketamine or dextromethorphan may be used.

See Also

• Opioid
• Hyperalgesia
• Pain management
• Opioid withdrawal