Pharmacological treatment of opioid-induced hyperalgesia: a review of the evidence.

Opioids are commonly used to treat moderate to severe pain. Opioid-induced hyperalgesia is a paradoxical response to opioid agonists resulting in an increased perception of pain rather than an antinociceptive effect. Even though there is a debate regarding its clinical relevance, it is becoming a challenge in both acute and chronic pain settings. The study of opioid-induced hyperalgesia is an emerging field with multiple challenges faced by investigators with regard to defining the diagnosis and characterizing the findings. The objective of this study was to review the preliminary evidence related to the treatment and management of opioid-induced hyperalgesia. Lack of data, small patient numbers, short-term follow-up, and variations in study design limited the review. With the literature on this subject being sparse, this study attempts to provide a preliminary look at the available data and to set the stage for an eventual meta-analysis. Case reports in the literature have shown success with various pharmacological interventions. Possible treatment regimens include ketamine, dextromethorphan, and nonsteroidal anti-inflammatory drugs (NSAIDs), opioid switching, amantadine, buprenorphine, α(2) agonists, and methadone. These agents are briefly discussed in this paper. Further well-designed, placebo-controlled trials are needed to assess the effectiveness of the interventions investigated in this review.