Cannabinoids for treatment of chronic non-cancer pain; a systematic review of randomized trials

Effective therapeutic options for patients living with chronic pain are limited. The pain relieving effect of cannabinoids remains unclear.
A systematic review of randomized controlled trials (RCTs) examining cannabinoids in the treatment of chronic non-cancer pain was
conducted according to the PRISMA statement update on the QUORUM guidelines for reporting systematic reviews that evaluate
health care interventions. Cannabinoids studied included smoked cannabis, oromucosal extracts of cannabis based medicine, nabilone,
dronabinol and a novel THC analogue. Chronic non-cancer pain conditions included neuropathic pain, fibromyalgia, rheumatoid
arthritis, and mixed chronic pain. Overall the quality of trials was excellent. Fifteen of the eighteen trials that met the inclusion criteria
demonstrated a significant analgesic effect of cannabinoid as compared with placebo and several reported significant improvements in
sleep. There were no serious adverse effects. Adverse effects most commonly reported were generally well tolerated, mild to moderate
in severity and led to withdrawal from the studies in only a few cases. Overall there is evidence that cannabinoids are safe and
modestly effective in neuropathic pain with preliminary evidence of efficacy in fibromyalgia and rheumatoid arthritis. The context of
the need for additional treatments for chronic pain is reviewed. Further large studies of longer duration examining specific
cannabinoids in homogeneous populations are required.