Buprenorphine--a review of its role in neuropathic pain.

BACKGROUND The use of opioids for the treatment of neuropathic pain remains somewhat controversial, since earlier studies indicate that neuropathic pain is generally less responsive to pure micro-opioid analgesia. A growing body of evidence now suggests that different opioids affect different pain pathways, and emerging data support the possibility of a role for buprenorphine in the management of neuropathic pain. OBJECTIVE This article reviews the preclinical and clinical data for the role of buprenorphine in the treatment of neuropathic pain. RESEARCH DESIGN AND METHODS Literature searches were carried out using PubMed (1988 to September 2006). Search terms included buprenorphine and neuropathic pain, as well as neuropathy, painful neuropathy, hyperalgesia, and allodynia. Clinical studies and case studies were included. RESULTS Several assays, including the formalin, cold tail flick, and diffuse noxious inhibitory control tests, have revealed buprenorphine's potential efficacy in various pain types. These findings seem to support hypotheses regarding its unique analgesic mechanisms as compared with pure micro-opioids. The exact mechanism of this analgesic efficacy remains unknown. Preclinical assessments of buprenorphine demonstrate its sustained antihyperalgesic effect in several models of neuropathic pain. These findings are supported in clinical studies of oral, intrathecal, intravenous, and transdermal buprenorphine. Furthermore, these studies have demonstrated that, despite there being a ceiling effect for respiratory depression, no relevant analgesic ceiling effect is found with buprenorphine. CONCLUSIONS Further studies are certainly warranted to identify the clinical neuropathic syndromes that are most sensitive to buprenorphine treatment, and to compare buprenorphine with other opioids in head-to-head trials of neuropathic pain.