There is no strong evidence to back a licensed cannabis-extract medicine which the Department of Health plans to make available to multiple sclerosis patients next year, according to a study.
The drug, Sativex, is used in the treatment of muscle spasms in sufferers of the disease. According to the study's findings, the strength of any evidence is insufficient to warrant its routine use.
In addition, a change in the law will be needed here before doctors are allowed to prescribe it for patients.
The study, led by Dr James Cave, editor of the 'Drugs and Therapeutic Bulletin' (DTB), which is part of the British Medical Journal group, examined the effects of the drug – given in the form of a mouth spray – which contained the extracts dronabinol and cannabidiol from the cannabis plant.
It is estimated that 8,000 Irish people have multiple sclerosis. An increase in muscle tone, or 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 don't work that well and have a range of unpleasant side-effects.
Sativex is intended for use by patients where other options have failed. But the DTB review found that the trial data on which the success of Sativex is based are limited.
Overall, the trials did show a small difference, where in a number of patients the symptoms lessened.
But the DTB review says that 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 suggests.
The preparation is also expensive, costing around 10 times as much as other drugs used for the secondary treatment of MS muscle spasms.