There is no strong evidence to back the use of cannabis extract in the treatment of multiple sclerosis (MS), it was claimed yesterday.
A review of evidence on the first licensed preparation made from an extract of the drug, Sativex, said there were “limitations” which made it difficult to identify the place of the product in clinical practice.
However, the makers of the drug said they believed the comments gave a misleading view and that the review writers appeared to have misunderstood important elements of the trials which were carried out.
Scotland is believed to have the highest rate of MS in world, with approximately 10,500 diagnosed cases. A further 60,000 in England and Wales are affected. It is estimated around one in every 1,000 people will develop the condition in the UK,
Sativex, in the form of a mouth spray, contains the principal extracts – dronabinol and cannabidiol – found in the leaf and flower of the cannabis plant, and is the first cannabinoid preparation to be licensed for use in the treatment of muscle spasms in MS.
An increase in muscle spasticity is a common symptom of the condition, causing involuntary spasms, immobility, disturbed sleep, and pain.
Complex combinations of drugs are sometimes needed to manage spasticity, but they do not work that well and have a range of unpleasant side-effects, the DTB says. Sativex is intended for use as a second-line treatment in patients in whom these other options have failed. But the review said the trial data on which the success of Sativex is based are limited.
Overall, the trials, on which the drug’s approval was based, did show a small difference in the numbers of patients in whom symptoms abated compared with those taking a placebo preparation, it said.
But in many of these studies, Sativex was used for relatively short periods – from six weeks to four months. And none included an active ingredient with which the effects of Sativex could be compared.
Two of the trials included doses that exceeded the 12 daily sprays for which the preparation is licensed, it said.
The preparation is also expensive, the review added, and costs around 10 times as much as other drugs used for the secondary treatment of MS muscle spasms.
The review, which appears in the December issue of Drug and Therapeutics Bulletin (DTB), says the strength of the evidence is insufficient to warrant its routine use.
“We believe that such limitations make it difficult to identify the place of this product in clinical practice,” it concludes.
GW Pharmaceuticals, the drug’s maker, said: “We are disappointed with the conclusions drawn and strongly believe these comments give a misleading view of the drug.”
A spokesman said the drug had been licensed in the UK by the Medicines and Healthcare Products Regulatory Agency (MHRA) in 2010.
Dr Stephen Wright, the company’s research and development director, said: “The writers appear to have misunderstood important elements of the design of Sativex clinical trials and provide a flawed assessment of Sativex data.”