Collaboration of Nadia Gomez.

Opioids

Opioids are very potent and effective drugs; they are traditionally used for both acute and chronic pain conditions. However, opioids commonly cause vigorous side effects, some of which are likely to become lethal.

The opioid signaling system has the greatest receptor for tolerance development; consequently, requiring some cases to increase the intake amount of the drug to fulfill the analgesic effect.

Opioid Induced Hyperalgesia (OIH)

Opioid induced hyperalgesia (OIH), is defined as a heightened response to painful stimuli, caused by opioid consumption.

This manifests as either hyperalgesia (increased/extreme sensitivity to pain), or allodynia (pain caused by stimulus that normally does not provoke pain); it becomes more intense while the dose and exposition duration are increased. The outcome varies according to characteristics of each patient.

Diagnosis

OIH is difficult to recognize due to the variation of symptoms among patients, resulting in a diagnosis of exclusion. It should not be the first diagnosis of any case, even if the patient has been on long-term opioid treatment.

Clinicians should suspect OIH when opioid effect decreases, without disease progression, especially if there is unexplained pain reports or allodynia unassociated with the original pain, and increased pain with increasing dosages.

Common opioids

The opioids used, in order of frequency, are morphine, fentanyl, oxycodone, hydromorphone, and methadone. The administration can vary in all forms: oral, intravenous, transcutaneous, transmucosal, and intrathecal.     

Management

Opioid cessation, opioid rotation, and auxiliary pharmacotherapies, such as ketamine and dexmedetomidine. Adjuvant drugs appear to be the most effective approach in terms of absolute decrease in opioid use.

Opioid induced hyperalgesia can be resolved when this condition is diagnosed and managed.

  • References
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