Clinical question
Compared with placebo or conventional drugs, how effective are cannabis-based medicines (CBMs) for conditions with chronic neuropathic pain in adults?
Bottom line
There was no high-quality evidence for the efficacy of any CBM (herbal cannabis, plant-derived tetrahydrocannabinol [THC] or dronabinol, synthetic THC [nabilone], plant-derived THC/cannabidiol [CBD] combination) in any condition with chronic neuropathic pain. The studies were 2–26 weeks in duration and compared an oromucosal spray with a plant-derived combination of THC and CBD (10 studies), a synthetic cannabinoid mimicking THC (nabilone; 2 studies), inhaled herbal cannabis (2 studies) and plant-derived THC (dronabinol; 2 studies) against placebo (15 studies) and a dihydrocodeine analgesic (1 study). Herbal cannabis was not different from placebo in reducing pain and the number of people who dropped out due to side effects. Some adverse events (particularly somnolence or sedation, confusion, psychosis) might limit the clinical usefulness of cannabis-based medicines.
Caveat
The quality of evidence for pain relief outcomes reflects the exclusion of participants with a history of substance abuse and other significant comorbidities from the studies, together with their small sample sizes.
Context
Estimates of the population prevalence of chronic pain with neuropathic components range between 6% and 10%. Cannabis has been used for millennia to reduce pain. Herbal cannabis is currently strongly promoted by some patients and their advocates to treat any type of chronic pain.
Cochrane Systematic Review
Mucke M et al. Cannabis-based medicines for chronic neuropathic pain in adults. Cochrane Reviews, 2018, Issue 3. Art. No.: CD012182.DOI: 10.1002/14651858. CD012182.pub2. This review contains 16 studies involving 1750 participants.
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