From the Guidelines
Identifying opioid-induced hyperalgesia (OIH) requires careful assessment of pain patterns that paradoxically worsen despite increasing opioid doses, as evidenced by the most recent study in 2018 1. To identify OIH, look for key signs including:
- Pain that becomes more diffuse or extends beyond the original site
- Increased pain sensitivity (allodynia)
- Pain that worsens with dose escalation
- Diminishing analgesic effects despite higher doses Patients may report that the pain feels different in quality compared to their original pain. It is essential to differentiate OIH from tolerance, as tolerance typically improves with dose increases while OIH worsens, as noted in a study published in the Annual Review of Medicine 1. Management involves:
- Gradually tapering the current opioid
- Possibly rotating to a different opioid like methadone or buprenorphine
- Adding adjuvant medications such as ketamine, gabapentinoids, or NSAIDs
- Implementing non-pharmacological pain management strategies OIH occurs because prolonged opioid exposure can cause neuroplastic changes in the central nervous system, including NMDA receptor activation and increased production of excitatory neurotransmitters, which paradoxically amplify pain signaling pathways, as discussed in a study published in the Annals of Internal Medicine 1. Early recognition is crucial as continuing to increase opioid doses will exacerbate rather than relieve the patient's pain, highlighting the importance of careful assessment and management of OIH, as supported by the most recent evidence 1.
From the Research
Identifying Opioid-Induced Hyperalgesia
To identify if somebody has opioid-induced hyperalgesia (OIH), the following points should be considered:
- OIH is a state of nociceptive sensitization caused by exposure to opioids, leading to a paradoxical response where a patient receiving opioids for pain treatment becomes more sensitive to certain painful stimuli 2.
- Clinical features of OIH can be observed in patients of both sexes, all ages, and with various types of pain treated with different classes of opioids 3.
- OIH can be diagnosed clinically, and its symptoms can be resolved when the condition is diagnosed and managed 3.
- Key signs that may indicate OIH include:
- Unexplained pain reports or diffuse allodynia unassociated with the original pain
- Increased levels of pain with increasing dosages of opioids
- Waning effect of opioid treatment in the absence of disease progression 2
Mechanisms and Risk Factors
The mechanisms of OIH are thought to be multifactorial, involving:
- Medullary descending pathways 4
- Central glutaminergic system 2
- Spinal dynorphins 2, 5
- Descending facilitation from the rostral ventromedial medulla 5
- N-methyl-D-aspartate (NMDA) receptors 2, 6, 5 Patient risk factors, opioid mitigation, and both pharmacologic and non-pharmacologic strategies should be considered to prevent OIH 4.
Diagnosis and Differentiation
It is crucial for clinicians to differentiate amongst clinically worsening pain, tolerance, and OIH, as the treatment of these conditions differs 5. A suggested clinical definition and directions for clinical differentiation of OIH from other diagnoses can be used to guide diagnosis 4.
Treatment Options
Treatment options for OIH include: