Multiple Sclerosis sufferers learned today that they can be prescribed a cannabis-based spray treatment for pain relief, even though it is not yet licensed in the UK.

The announcement sent the share price of the company that produces the medicine rocketing on the stock market.

GW Pharmaceuticals, a medical research and development company based in Salisbury, Wiltshire, said it had been told by the Home Office that it would allow doctors to prescribe Sativex to select MS patients, based on their individual needs.

The treatment - which has been found to significantly reduce pain in the central nervous system among those hit by the disease - has until now only been available in Canada.

After receiving approval from the Canadian medical authorities in April, Sativex has been available on prescription there since late June.

The drug will now have to be imported from Canada to the UK, where it will remain a tightly controlled, Schedule 1 drug. There are about 85,000 MS sufferers in the UK, of which around two-thirds are women.

Doctors have wanted to be able to prescribe Sativex to their patients, amid widespread use by MS sufferers of pure cannabis to combat pain relief. Cannabis remains a Class C drug, for which even possession can result in arrest. GW had previously been granted the right to grow the drug legally in Britain for testing and refining purposes.

The approval means Sativex becomes the only cannabis-based drug to become available on prescription in the UK.

"This development is in response to enquiries from a number of UK doctors and individual patients who have been in contact with the Home Office to request access to Sativex," GW Pharmaceuticals said today.

Steve Barker, a spokesman for the Campaign to Legalise Cannabis, said: "It's great news... I think this will be a relief for the huge number of MS sufferers and thousands of sufferers of chronic pain.

"Presumably it's a toe in the water as far as the Government is concerned. They'll want to see how it goes."

Before the Misuse of Drugs Act in 1971, cannabis could be prescribed by GPs. In the 1920s, it was routinely used to treat more than 20 medical conditions.

GW said that now, doctors will only be able to prescribe the drug to patients under licence from the Home Office, which will now develop a licensing regime to accommodate the controversial nature of the ingredients. But the drug should be immediately available to patients, once their GPs have carried out the necessary paperwork.

The company added: "GW expects to discuss the implementation practicalities with the Home Office over the coming weeks. GW, which is still carrying out final stage trials for Sativex, said it would pursue its application for a full UK licence for the drug."

Shares in GW Pharmaceuticals, which is listed on the London Stock Exchange's junior AIM market, soared following the disclosure of the approval, which should act as a strong boost to the company's business in the UK.

Having closed last night at 70p, the shares jumped more than 18.5 per cent to 83p, substantially increasing GW's value, which based on yesterday's close stood at just under £80 million.

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