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25-10-2018 | Multiple sclerosis | News | Article

Medicinal cannabinoids show small antispastic and analgesic benefits for MS patients

medwireNews: The benefits of medicinal cannabinoids for the treatment of spasticity, pain and bladder dysfunction in patients with multiple sclerosis (MS) may be limited, suggests a systematic review and meta-analysis.

But the drugs were well tolerated “as the analysis of serious adverse events did not show statistical significance,” note the investigators in JAMA Network Open.

The team identified 17 randomised, placebo-controlled, double-blind and parallel or crossover trials that involved 3161 patients with MS who had received cannabinoids or placebo for at least 2 weeks.

Four medicinal cannabinoids were assessed: oral cannabis extract, oromucosal nabiximols, oral dronabinol and oral nabilone.

The results showed a significant clinical effect of cannabis extract and nabiximols, and of cannabinoids overall, on subjective measures of spasticity versus placebo, with standardised mean differences (SMDs) ranging from ─0.25 to ─0.29 standard deviations (SD).

However, cannabinoids had no effect on objective spasticity, as measured on the Ashworth and Modified Ashworth scales.

“Differences among results might stem from the fact that a minor improvement in such a disabling symptom is reflected by a more positive evaluation from the patient”, Mari Carmen Torres-Moreno (Universitat Autònoma de Barcelona, Spain) and colleagues suggest.

The results were similar for pain, with SMDs in favour of cannabis extract and nabilone and cannabinoids overall ranging from ─0.17 SD to ─1.40 SD. And for bladder dysfunction, a clinical effect over placebo was seen for cannabinoids that was driven by the effects of cannabis extract, with SMDs of ─0.11 and ─0.29, respectively.

The researchers say that the “small value of SMD […] represents a limited (small) therapeutic effect.”

A total of 5357 adverse events were analysed and the risk of these was significantly higher with nabiximols, dronabinol and cannabinoids overall than with placebo, with respective rate ratios (RRs) of 1.80 patient─years, 1.62 patient─years and 1.72 patient─years.

The risk of withdrawal due to adverse events was also significantly increased for cannabis extract (RR=3.11 patient─years), nabiximols (RR=2.20 patient─years), dronabinol (RR=4.12 patient─years) and cannabinoids (RR=2.95 patient─years), but not for nabilone.

There was no difference between the active drugs and placebo in the risk of serious adverse events, however.

The researchers report that sensitivity analysis “showed no relevant differences affecting the results obtained.” They therefore consider the results “to have a high level of certainty.”

In a related commentary, Marissa Slaven and Oren Levine, both from McMaster University in Hamilton, Ontario, Canada, commended the researchers on “a methodologically sound meta-analysis”, but they point out that the trials included were “relatively weak”.

They say that “[g]iven 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 MS.”

But they add that “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 MS.”

By Lucy Piper

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