Is cannabis the new wonder drug?
Cannabis was first recommended as a medicine 5,000 years ago in the reign of the Chinese emperor Chen Nung, for malaria, constipation and absentmindedness. In Britain it is now a schedule one drug (alongside ecstasy and LSD). Its sole medical use is limited to preventing nausea and vomiting in patients having chemotherapy for cancer.
This month sees the launch of an advertising campaign by the Alliance for Cannabis Therapeutics to increase its availability for medical treatment. "I can't prescribe you a safe, naturally occurring drug for the pain of Multiple Sclerosis, but I can give you heroin" says one advert. Heroin, (diamorphine) is a schedule two and in government terms, more medically acceptable drug.
Later this year the Royal Pharmaceutical Society and the Multiple Scelerosis Society will jointly host a conference on the potential medical benefits of the drug. It was meant to happen this month but such is the political sensitivity surrounding the subject that the Home Office was unwilling to take part so close to an election.
The BMA is also expected to produce a report this year stating its position, which is likely to say "more research is needed." Most of the evidence that cannabis is useful in some conditions - notably the wasting that accompanies Aids, nausea from chemotherapy, chronic pain, muscle spasm in MS, glaucoma (a cause of blindness), asthma and epilepsy, is anecdotal or based on small studies. But no one would question it's relative safety compared to more legal drugs. No one has died from taking it - the ratio of its effective dose to a lethal dose is 1 in 20,000. You would need to consume 1,500 pounds of the stuff in 15 minutes to have a hope of killing yourself.
Many doctors would be happy to prescribe it. The New England Journal of Medicine, an academic rather stuffy organ, had an editorial earlier this year protesting at the US government's plans to penalise doctors who prescribed cannabis: "A federal policy that prohibits physicians from alleviating suffering by prescribing marijuana for seriously ill patients is misguided, heavy handed and inhumane."
Cannabis is known as a "dirty" drug, because it contains at least 30 active ingredients (cannabinoids). The main psychoactive one (responsible for euphoria and occassional paranoia) is THC (delta9-tetrahydrocannabinol). The only prescribable one in Britain is Nabilone, a tablet which is only available for the side-effects of chemotheraphy. Anecdotally many patients get more benefit from smoking the drug in its dirtier form.
"the absorption from the gut is unpredictable and once you've taken the tablet you are committed to that dose," says Dr. Roger Pertwee, a reader in biomedical sciences at Aberdeen University, who is carrying out research into cannabinoids. "It's also slower to take effect. With smoking it is easier to control your dose." Doctors would, however, find it hard to advise their patients to smoke anything. Research is looking at skin patches and aerosols to deliver the drug.
"The effects of cannabis are not something we can't explain," says Pertwee. "Cannabinoids have precise effects. The brain has cannabinoid receptors. There probably is some use for cannabis in patients whose symtoms are not controlled by existing drugs, particularly when those drugs have unpleasant side-effects. We should try to exploit whatever potential it has."
SMOKE SIGNALS
What's known already:
Anticonvulsant - A study of Cannabidiol, a cannabinoid, found improvement in seven patients with uncontrollable seizures compared to none in eight patients given an inactive drug.
MS - Smoking cannabis reduces muscle spasm, tremors, night leg pain, and depression in some sufferers, according to small trials.
Anti-sickness - No studies have compared it to the best legal anti-sickness drug, ondanestron, but research suggests it works as well as other drugs.
Glaucoma - In glaucoma the pressure within the eye is raised and can cause blindness. Studies in animals and humans show cannabis (smoked or taken orally) reduces the pressure by a third.
Pain relief - Much anecdotal evidence, particularly in arthritis, Aids, migraine and cancer suffers.
Asthma - Cannabis through an aerosol spray opens up the airways. No prpoer trials reported.
Side-effects - Smoking cannabis can impair short-term memory and learning for a few weeks. Inconclusive evidence that it increases risk of developing schizophrenia in heavy users. Can cause lung cancer and bronchitis.
Luisa Dillner.
© 1999 The Guardian
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