Medical cannabis for the reduction of opioid dosage in the treatment of non-cancer chronic pain: A systematic review
Abstract Background: Medical cannabis (MC) is currently being used as an adjunct to opiates given its analgesic effects and potential to reduce opiate addiction. This review assessed if MC used in combination with opioids to treat non-cancer chronic pain would reduce opioid dosage.Methods: Four databases - Ovid (Medline), Psyc-INFO, PubMed, Web of Science, and grey literature – were searched to identify original research that assessed the effects of MC on non-cancer chronic pain in humans. The search yielded 4,316 articles and 24 reports from the databases and grey literature, respectively. Results: Nine studies involving 7,222 participants were included. There was a 64%-75% reduction in opioid dosage when used in combination with MC. Use of MC for opioid substitution was reported by 32%-59.3% of patients with non-cancer chronic pain. One study reported a slight decrease in mean hospital admissions in the past calendar year (P=.53) and decreased mean emergency department visits in the past calendar year (P=.39) for patients who received MC as an adjunct to opioids in the treatment of non-cancer chronic pain compared to those who did not receive MC. Conclusions: While this review indicated the likelihood of reducing opioid dosage when used in combination with MC, the optimal MC dosage to achieve opioid dosage reduction remains unknown. More research is needed to elucidate whether MC used in combination with opioids in the treatment of non-cancer chronic pain is associated with health consequences that are yet unknown.Systematic review registration: This systematic review was not registered.