Friday, 7 November, 2003
The biggest-ever trial of "cannabinoid" drugs in MS has produced mixed
While patients told researchers that their symptoms were eased by the drugs, there was relatively little hard evidence of physical changes in their bodies to back this up.
BBC News Online looks at the implications of the trial for future use of cannabis in medicine.
What prompted researchers to look at the benefits of cannabis in multiple sclerosis?
Many MS patients have been using cannabis illegally for years to help them overcome some of the more distressing symptoms associated with the illness.
Patients often suffer painful muscle spasms and stiffness, termed "spasticity" by doctors.
Other symptoms include tremor, sleep disturbance and bladder problems.
While the "high" caused by smoking cannabis is well-documented, many scientists believe the cocktail of chemicals the plant contains can produce other physical effects in the body.
MS patients say smoking cannabis brings far more relief from some of their painful symptoms compared with conventional painkillers.
This anecdotal evidence is not a convincing reason to supply it on the NHS - hence the large scale, Medical Research Council study running over a five year period.
What did the researchers give the patients?
Simply giving them the street drug was ruled out - it was considered unethical because there are genuine health concerns associated with smoking the drug.
Instead, they decided to test a cannabis extract, containing a range of chemicals from the drug, and a synthetic version of one in particular, called THC, which is believed to be the chemical which holds the key to many of the reported "beneficial" effects of cannabis.
Another group of patients was given a "placebo" drug, a dummy pill, so that the response of those taking the active tablets could be properly compared.
How did they check how effective the drugs were?
The key measure of success would be an improvement in "spasticity" - the muscle stiffness and spasm.
There were two ways of measuring this - firstly, a scoring system administered by a physiotherapist, who assessed stiffness in each muscle group.
Secondly, the patients themselves were asked whether they felt their symptoms had improved, along with overall MS pain, sleep disturbance, tremor, mood and bladder control.
They were also timed walking along a 10 metre course both before treatment and during it.
What were the results?
The key measure of spasticity - the scoring system - revealed no significant improvement using the cannabinoid drugs.
The other physical measure of improvement - the walking test - showed a slight improvement with the drugs.
However, significantly more patients in the group getting active treatment said their symptoms were much better as a result.
Why the conflicting results?
The researchers say that it is possible that their scoring system is simply not sensitive enough to pick up modest physical changes that make a big difference to how an MS patient feels.
Rather than actually easing stiffness, the drugs may be working as very effective painkillers to change how patients' perceive their condition, they say.
Does this mean that the drugs could be available more widely to MS patients?
It could help in the long term. The researchers say it does not provide definitive proof that the drug is having a physical effect.
However, they say that the experiences of so many patients claiming improvements cannot be ignored.
One drug company is already thought to be applying for a licence to market a cannabis-based drug for MS patients.
This large-scale study provides an excellent framework for further research.
There do not seem to be any issues over the safety of this medication, and patients do not experience any of perceptual effects related to the street drug, as the psychoactive ingredients are either not present or delivered in too low doses.
Why is there controversy over cannabinoid drugs?
There is more acceptance that cannabis will eventually prove the source of some kind of useful drug.
There are plenty of precedents for powerful and illegal recreational drugs becoming, with a little adaptation, medical mainstays.
The best example is opium, which is widely used in its pure form as
morphine in hospitals worldwide.
Copyright © 2003, BBC