Uncertainty Remains Over Treating Multiple Sclerosis Symptoms with Medical Marijuana

The use of marijuana for patients with multiple sclerosis can have a limited effect on symptoms such as spasticity, pain, and bladder dysfunction, according to a recent study.

Although cannabinoids have antispastic and analgesic effects, their role in the treatment of multiple sclerosis is not clearly defined. Investigators conducted a systematic review and meta-analysis of published literature on the use of medical marijuana in patients with multiple sclerosis in order to examine the effectiveness and tolerability of the drug compared with placebo in patients looking to treat their symptoms. They pulled studies from Medline and the Cochrane Library Plus through July 2016 without applying any restrictions and found 17 viable studies that included more than 3000 adult patients. Some of the experimental cannabis extract interventions included oral cannabis extract, oromucosal cannabis extract (nabiximols), oral dronabinol, and oral nabilone. Each intervention was evaluated as an adjunctive treatment to gabapentin.

The use of cannabis extract was associated with a limited and mild reduction in the patients’ own assessment of spasticity, pain, and bladder dysfunction, the investigators reported. Spasticity measures showed significant differences among the treatments of cannabis extracts, nabiximols, and cannabinoids. The researchers said these differences were likely attributed to the style of each study’s masking and blinding methods. The researchers found that treatment for pain differed among the patients, showing slight favor to cannabis extract, nabilone, and cannabinoid interventions. Similar results were demonstrated in measures for bladder dysfunction, favoring cannabis extract and cannabinoids.

One limitation noted by the investigators in their meta-analysis was the inclusion of industry-funded studies. The cannabis extract and dronabinol studies were funded by independent grants; however, the nabilone and nabiximols were funded by pharmaceutical companies.

When the study authors ran their analysis excluding the industry-funded studies, there were no differences between nabiximols and placebo in the efficacy outcomes. However, the spasticity values changed in the industry-funded studies, and the investigators said that suggested sponsored studies favored active treatment.

Across the analysis, there were 5357 adverse events. Some of the common adverse events were dizziness or vertigo, dry mouth, fatigue, feeling drunk, impaired balance or ataxia, memory impairment, and somnolence. There was a higher risk of adverse events in active treatments compared with placebo in nabiximols, dronabinol, and cannabinoids. A total of 260 patients withdrew because of adverse events, and there was a higher risk for withdrawals due to adverse events in those taking cannabis extract, the investigators determined. In total, they reported 325 serious adverse events.

“Cannabinoids produce a limited and mild reduction of subjective spasticity, pain, and bladder dysfunction in patients with multiple sclerosis, but no changes in objectively measured spasticity,” the study authors concluded. “They can be considered safe drugs, as the analysis of serious adverse events did not show statistical significance, although the total number of adverse events is higher than in placebo for the treatment of symptoms in patients with multiple sclerosis.”

In a related editorial, Marissa Slaven, MD, and Oren Levine, MD, MSc, assistant professors at McMaster University in Ontario, Canada, argued that the way forward for medical marijuana as a multiple sclerosis treatment remains unclear.

“In light of uncertainty around clinically meaningful benefit and heterogeneity of the studies and results, [the study authors] appropriately avoid drawing strong conclusions regarding the role for cannabinoids in managing symptoms of multiple sclerosis,” they wrote. “Given the relative safety of these agents, lack of strong evidence of other effective treatment options, and increasing access in some jurisdictions, it may seem appealing to include cannabinoids in the armamentarium of therapies for multiple sclerosis. But, carefully conducted, high-quality studies with thought given to the biologic activity of different cannabis components are still required to inform on the benefits of cannabinoids for patients with multiple sclerosis.”

The study, “Assessment of Efficacy and Tolerability of Medicinal Cannabinoids in Patients With Multiple Sclerosis,” was published in JAMA Network Open.