Ashton, J.C., & Milligan, E.D. (2008). Cannabinoids for the treatment of neuropathic pain: Clinical evidence. Current Opinion in Investigational Drugs, 9, 65–75.

The purpose of the study was to determine if cannabinoids are useful in treating neuropathic pain.

No specific databases were stated. Key words included ajulemic acid, analgesia, cannabidiol, cannabinoid, cannabis, CB1 receptor, CB2 receptor, ∆9-tetrahydrocannabinol, dronabinol, levonantradol, nabilone, neuropathic pain, and Sativex. Studies were included if they directly assessed pain; studies were excluded if they assessed pain indirectly by indices of general effects (i.e., quality of life or improvement in sleep).

The total number of studies initially reviewed was not stated; however, the final sample included 18 clinical studies from 2000–2008, 2 studies from prior to 2000, and 3 major reviews and/or meta-analyses. The method of study evaluation was not reported.

The sample range across studies was not stated, but characteristics included neuropathic pain from a variety of conditions, including cancer-related neuropathy.

Substantial evidence shows that cannabinoids are beneficial in reducing neuropathic pain from a variety of causes, including CIPN. One notable study prior to 2000 included 36 patients with cancer pain. Two of the reviews and meta-analysis also included studies of people with cancer-related pain. The findings from this subset were not discussed.

Cannabinoids can be useful as an adjuvant medication for treatment of neuropathic pain; however, side effects such as somnolence, ataxia, dry mouth, euphoria, and dizziness limit their acceptance and tolerance with patients. The authors concluded that, while cannabinoids are moderately effective for the treatment of neuropathic pain, cannabinoid drugs with less psychoactivity should be developed.

This report was limited by lack of specific information related to the literature search and sample sizes of studies included.

Based on the data presented, use of cannabinoids are likely effective for treating neuropathic pain in patients with cancer; however, their psychoactive side effects may limit their acceptability and tolerability.