Many people taking opioids like oxycodone or Oxycontin (pharmaceutical grade heroin) for an extended length of time report that the opioid dose that they are taking is no longer providing the analgesic (pain relief) benefit for which it was prescribed.  In the past, medical researchers attributed the need to increase the dosage for many people taking opioids to increased tolerance to the opioids.

Now, there is increasing empirical evidence that after several months, in many people opioids start making the pain receptors more sensitive.  If thees people begin to take more and more of the opioid, the evidence shows that the pain receptors become more sensitive and the analgesic effect of the opioids is further reduced. This condition is called opioid-induced hyperalgesia (increased sensitivity to pain).

Patients experiencing opioid-induced hyperalgesia often ask their doctors to prescribe  higher and higher doses.  However, each increase in the dosage of the opioid increases the sensitivity of the receptors and does not, except initially, provide analgesic relief.  This is a cycle that continues until the patient cannot tolerate any additional dosage of the opioids.

Because opioids are central nervous system depressants, people experiencing opioid-induced hyperalgesia can take a higher dosage than their body can tolerate and, in some cases, not be able to function or even suffer serious health complications.