Wednesday, 21 August, 2002, 15:53 GMT 16:53 UK
Scientists have developed a cannabis-based medicine which relieves chronic pain without any of the "high" normally associated with the drug.
They believe the discovery could pave the way for cannabis-based medication to become available by prescription within two years.
Much of the controversy surrounding the medicinal use of cannabis has centred on fears that it would be used solely for its mood-altering effects.
However, scientists at the University of Massachusetts in the United States say their discovery should help authorities to overcome these fears.
Dr Sumner Burstein and colleagues say early trials of the medication in animals and healthy patients have been promising.
The medication, called ajulemic acid or CT3, has been manufactured in laboratories.
It maximises the medicinal effects of tertrahydrocannabinol - the key ingredient of cannabis - without any of the mind-altering effects.
In animal tests, this compound was found to be between 10 to 50 times more effective at reducing pain than tetrahydrocannabinol.
Those tests showed that ajulemic acid was very effective at preventing the joint damage associated with arthritis and relieving the muscle stiffness associated with multiple sclerosis.
The compound was tested last year in 15 healthy volunteers in France. That study reported no side effects or mood changes in those participants.
A further trial on 21 patients with chronic severe pain is currently underway in Germany.
Dr Bernstein said the results of each study had been promising.
"The indications so far are that it is safe and effective," he said.
Dr Bernstein added that the compound could replace a wide variety of current medicines used to fight pain.
"We believe that [the compound] will replace aspirin and similar drugs in most applications primarily because of a lack of toxic side effects."
Dr Bernstein acknowledged that some patients may wish to experience the mood-altering effects of cannabis by taking this compound.
But speaking at the national meeting of the American Chemical Society in Boston, he added: "The medical community wants efficacy without this effect."
A spokeswoman for the UK's Medicinal Cannabis Research Foundation said:
"We believe it would be premature to comment on the merits of ajulemic
acid before more rigorous testing in patients has been carried out, but
look forward to seeing the results after further study."
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