In America, cannabis has been successfully used to ease nausea and restore the appetites of cancer patients and people suffering weight loss because of Aids. Now in Britain there is growing interest in the use of cannabis to relieve pain, particularly in cases of terminal illness, and in alleviating symptoms of multiple sclerosis.
'Marijuana is one of the least toxic substances in the whole pharmacopoeia,' says Dr Lester Grinspoon, professor of psychiatry at Harvard Medical School and an adviser on drugs policy to the new government. 'It has an extraordinary range of medical applications which have been neglected by medicine thanks to a misinformation campaign by the federal government,' he says.
Most evidence of the therapeutic value of cannabis comes from the US. However, the Alliance for Cannabis Therapeutics, based in Washington, is helping to form a British branch that will press for legal reforms. In Britain, the prescribing of cannabis for therapeutic use is forbidden under the 1971 Misuse of Drugs Act.
Official interest in marijuana's therapeutic properties is growing in the US. Until the anti-smoking and anti-drugs lobbies joined forces, compassionate 'government reefers' were available on a controlled basis for a small number of patients, including some men with Aids. In 1991, this programme was halted.
'We were using marijuana to treat Aids wasting, but the fear was that it might cause lung complications and hasten the death of people with Aids,' Bill Greg, a spokesman for the US Public Health Service, says.
In his forthcoming book, Marihuana, the Forbidden Medicine, Dr Grinspoon identifies epilepsy, paraplegia, migraine and menstrual pain as conditions that could be helped by cannabis. Much of his evidence comes from patients' subjective accounts of the drug's beneficial effects, but Dr Grinspoon claims cannabis has many advantages over modern drugs. 'People with Aids often suffer nausea as a result of taking the drug AZT. Smoking cannabis can often relieve the vomiting and slow down the diarrhoea associated with the condition.
'Aspirin was used as a substitute for cannabis to treat moderate pain. Yet between 500 and 1,000 people a year die because of bleeding caused by aspirin, and many people get hooked on various opiate derivatives,' he says.
Cannabis has been used in the West for more than 300 years, but it fell from favour at the turn of the 20th century with the arrival of aspirin and opiate drugs. The drugs laws that followed sealed its fate.
Culpeper's 17th-century Complete Herbal manual advised readers that cannabis: '. . . allays the troublesome humours of the bowels, eases pains and shrinkings of the sinews and too much use of it dries up the seed for procreation'. During its heyday in the 19th century, cannabis was widely used by European doctors to alleviate pain. Its muscle-relaxant properties were recognised and cannabis became so respectable it was even given to Queen Victoria by her court physician, according to the American historian E L Abel (Marihuana: the first 12,000 years, New York Plenum, 1980).
Dr Grinspoon argues that since cannabis is cheap to produce, it could reduce America's enormous drugs bill, which threatens to cripple the country's medical services. The use of cannabis seized during raids by the Drug Enforcement Agency has been suggested as a possible source of supply.
In Britain, news that cannabis might help to alleviate the painful muscle spasms associated with multiple sclerosis has spread quickly among those desperate for relief. The Multiple Sclerosis Society has been inundated with inquiries.
Dr James Malone-Lee, a consultant urologist at St Pancras Hospital, London, has several MS patients who smoke cannabis. 'It relaxes the sphincters, which allows them to empty their bladders. I'm quite impressed by what's happened to patients who have used it,' he says.
He is waiting on Home Office permission to study the effects of cannabis on bladder muscle. 'The standard muscle-relaxant drugs, such as dantrolene and baclofen, are not very good. There is no way we would experiment with humans at the moment - although I have to say I've had an awful lot of letters from people volunteering themselves,' he says.
A common objection to using cannabis is that it induces euphoria. However, the British National Formulary, a dictionary of drugs widely used by doctors, describes it merely as a 'mild hallucinogen . . . seldom accompanied by a desire to increase the dose'.
More reasonably, concerns about the effects of cannabis on the brain have cast doubts over its value to MS patients since their disorder is neurological. Dr Malone-Lee says: 'Frankly, if I had their spasticity and bladder difficulties, I would take cannabis and not be too fussed about the effect on the central nervous system.'
But the major drawback to the legal, therapeutic use of cannabis is the fact that it is a natural substance and is therefore very crude. It contains 60 active ingredients or 'cannabinoids'. Single cannabinoids have been isolated and manufactured synthetically and are available on prescription, but Dr Grinspoon claims these are less effective than the natural substance. And since cannabis is a plant, it cannot be patented, making it an unattractive commercial proposition.
Dr Anthony Henman, former secretary of the International Anti-Prohibition League, rejects these arguments. 'One of the best effects cannabis can have in any terminal illness is to produce a degree of euphoria, which boosts morale in a depressing situation,' he says.
'Cannabis should be available in the same way as tea and coffee. It is totally immoral to make it difficult for people to use these substances. There is a general move back to medicine based on organic compounds, fuelled partly by the feeling that the pharmaceutical industry has deliberately excluded the use of vegetable compounds for its own commercial gain.'
Despite developments in the US, cannabis is unlikely to become available through doctors in Britain for some time. Patients who smoke it to relieve their pain or stress will continue to do so unlawfully. 'It's tragic that people who take cannabis as a medicine have to add a layer of anxiety to the one they already have to deal with as a consequence of their illness,' Dr Grinspoon says.
'When cannabis is put into historical perspective some years from now, it will seem amazing that we behaved like this towards this drug.'