Opioid Induced Hyperalgesia (OIH) is a real condition. It occurs when opioid medications actually cause increased sensitivity to painful stimuli. Yes, it's a paradox but it does occur. It is difficult to diagnose because it is difficult to distinguish from opioid tolerance. But there are some characteristics unique to OIH:
- Pain in more diffuse in nature
- Pain worsens over time even if opioid dosage is increased
- Pain harder to pinpoint and of lesser quality
It is thought that the mechanism of OIH is most likely due to over-excitation of neurons, but at this point the jury is still out. If OIH is suspected, the offending medication is withdrawn slowly. Sometimes, if pain persists it may be possible to reduce the dose of the original medication or switch to another class of drugs for pain management. There is added difficulty in that a patient might have difficulty understanding how pain levels can actually increase because of their medication!
OIH is poorly understood and more research is needed to find the best path forward for those who experience it. The research continues on this front!
Sources: Medscape; Wikimedia