From the Guidelines
The likely cause of worsening pain in a patient taking opioid analgesics for chronic pain is opioid-induced hyperalgesia (OIH). This condition is characterized by heightened pain sensitivity despite escalating opioid doses, as noted in a study published in the Annual Review of Medicine in 2018 1. The development of opioid tolerance, which necessitates increasing the dose, facilitates the emergence of hyperalgesia. Key features of OIH include:
- Increased pain sensitivity
- Central sensitization
- Activation of N-methyl-D-aspartate (NMDA) receptors
- Potential for dose tapering or opioid discontinuation to ameliorate pain
Management strategies for OIH may involve:
- Opioid rotation, such as switching to a different opioid
- Dose reduction
- Implementing adjuvant non-opioid pain treatments, such as pregabalin, propofol, or COX-2 inhibitors, as suggested by the study 1
- Considering alternative treatments, like ketamine infusions, to reset pain pathways
It is essential to recognize OIH early, as continuing to increase opioid doses can worsen the condition, leading to a cycle of escalating pain and opioid use. By understanding the mechanisms and management strategies for OIH, clinicians can make informed decisions to improve patient outcomes and reduce the risk of opioid-related complications.
From the Research
Possible Causes of Worsening Pain
- The likely cause of worsening pain in a patient taking opioid analgesics for chronic pain is opioid-induced hyperalgesia (OIH), a state of nociceptive sensitization caused by exposure to opioids 2, 3, 4, 5.
- OIH is characterized by a paradoxical response whereby a patient receiving opioids for the treatment of pain may actually become more sensitive to certain painful stimuli 3, 5.
- This condition can be caused by neuroplastic changes in the peripheral and central nervous systems that lead to sensitization of pronociceptive pathways 3, 5.
Key Features of Opioid-Induced Hyperalgesia
- OIH can occur at any dose of opioids, but it is more commonly reported at high doses 4.
- Clinical features of OIH include increased sensitivity to pain, diffuse allodynia, and unexplained pain reports 3, 4, 5.
- OIH can be diagnosed clinically and managed with strategies such as opioid rotation, opioid cessation, and adjuvant pharmacotherapies 4.
Distinction from Other Conditions
- OIH is distinct from tolerance, which is addressed by increasing the opioid dose, whereas OIH requires a decrease in opioid dose 3, 6.
- OIH is also distinct from dependence, which is a separate condition that requires different management strategies 2, 3, 4, 5, 6.
- Neuroplasticity is a broader concept that refers to changes in the nervous system, but it is not a specific cause of worsening pain in this context 2, 3, 4, 5, 6.