SEATTLE – Reviewers found modest evidence of benefit and plenty of room for more research.
“Cannabis-based medicine may be useful for refractory MS symptoms, especially spasticity and pain, and side effects are usually well tolerated,” study lead author Natasha Breward, a graduate student at the College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, said in an interview. Ms. Breward spoke prior to the presentation of the study findings at the annual meeting of the Consortium of Multiple Sclerosis Centers.
For the review, Ms. Breward and colleagues focused on 60 studies - 26 randomized controlled trials and 34 trials with other designs. Forty of the studies used nabiximols (), an oromucosal spray that is derived from the cannabis sativa plant and approved for use in multiple countries but not yet in the United States.
According to Ms. Breward, some of the other treatments included dried cannabis that is smoked or eaten and cannabidiol that’s typically delivered with tetrahydrocannabinol (THC) either oromucosally or as an oral capsule.
MS symptoms treated in the studies included spasticity (n = 29), pain (n = 8) and cognition (n = 6).
The researchers considered 22 studies to be poor quality, 14 to be fair quality, and 24 to be good/excellent quality.
As for results, the researchers found that the cannabis-based medicine “significantly reduced spasticity and pain in several individual good-quality studies,” Ms. Breward said. The drugs seem to work by inhibiting neurotransmitter release via cannabinoids, she said.
“However,” she added, “the variability in study quality – and in the products and regimens studied – make it hard to draw any conclusions about specific products and doses that may have the most potential benefit.”
As for adverse effects, dried cannabis was linked to decreased long-term cognitive function, which is distinct from being temporarily high, Ms. Breward said.
“Further research should focus on the use of different products and formulations of cannabis-based medicine such as cannabis oil and cannabidiol-prominent products, as no studies have focused on this area,” she said. “Research should also look at the potential of cannabis-based medicine for the treatment of disease progression, as cannabinoids are anti-inflammatory and immunomodulatory. Finally, more research regarding the potentially synergistic effects of cannabis-based medicine administered with current MS medications would also be useful.”
No study funding is reported and the authors report no relevant disclosures.