Setback for calls to license pot, as derivatives cause side effects and prove less valuable than conventional drugs for pain relief

http://www.guardian.co.uk/uk_news/story/0,3604,517557,00.html

Sarah Boseley, health editor
Friday July 6, 2001
The Guardian

Cannabis derivatives are neither as effective nor as safe as conventional medicines for the relief of pain and prevention of sickness during cancer drug treatment, according to two reviews of existing evidence which will dismay those who hope to see marijuana licensed as a medicine.

However, neither study focused on the possible benefit to people suffering from multiple sclerosis. Cannabis derivatives are being tested on substantial numbers of people with MS and other neuropathic disorders as a result of sufferers' claims that smoking dope relieved their symptoms and their pain.

Recently a House of Lords select committee urged the medicines control agency to help speed up the process of licensing cannabis derivatives. The MCA, however, has said it may require further tests on the toxicity of one of the cannabinoids - the chemicals derived from breaking down the whole plant.

The review published today in the British Medical Journal suggests that cannabinoids do have an effect in pain and sickness relief, but that it is not great, and it warns of serious side effects that outweigh the benefits.

The authors acknowledge, however, that multiple sclerosis - where there are few useful drugs - may be a special case. One trial, examined during the review of pain control, showed not only that people who smoked marijuana felt that their symptoms had improved, but that their posture and balance measurably improved.

Fiona Campbell, from the pain management centre of the Queen's medical centre in Nottingham, collaborated with colleagues in Oxford and Switzerland to review all the trials that have been done into cannabinoids for pain management. They found nine relevant and acceptable studies, of which five related to cancer pain, two to acute pain after surgery and two to chronic pain.

The researchers found that cannabinoids were no more effective than codeine tablets in controlling pain. They depressed the nervous system, which would limit their use. "Their widespread introduction into clinical practice for pain management is therefore undesirable. In acute postoperative pain they should not be used," the authors said.

They and the team who reviewed the use of cannabinoids to prevent sickness in people undergoing chemo therapy, or toxic drug treatment for cancer, were alarmed by the side effects of the cannabinoids. "Adverse effects associated with the cannabinoids were common and sometimes severe in six of the eight trials that showed efficacy," said Dr Campbell and colleagues.

The result of the review of the chemotherapy studies was otherwise a little more optimistic. Martin Tramer, an anaes thetist from the University hospital of Geneva, Switzerland, and colleagues from the Oxford Radcliffe hospital in the UK looked at the results of 30 trials published between 1975 and 1997. They found the cannabinoids were slightly more effective than other drugs in preventing nausea and vomiting, and the patients preferred them. But the researchers said they caused so many damaging side effects that doctors would have to think hard about using them.

Tony Moffat of the Royal Pharmaceutical Society, who is on the steering committee for the trials of cannabinoids use in multiple sclerosis and pain relief funded by the Medical Research Council, said the papers were no reason to be dismayed; the trials had shown there was some effect in terms of pain relief.

The MRC pain relief trials, which will begin next month, involve 400 patients who have had surgery in London hospitals. The multiple sclerosis trial involves 660 patients and is based in Derriford hospital, Plymouth. The first 20 patients have been treated with no adverse effects.

A second set of trials is taking place, run by the commercial company GW Pharmaceuticals, which has developed a spray from the entire cannabis plant which is applied under the tongue. The company is already claiming great success and says using the whole plant gets better results than stripping it down to derivative cannabinoids.

"In the last 18 months GW has carried out clinical trials in 75 patients suffering from multiple sclerosis, spinal cord injury, neuropathic pain, other intractable neurological conditions and rheumatoid arth ritis," said Philip Robson, the company's medical director. "We are seeing clinically significant improvements in a range of symptoms, including pain, muscle spasms, spasticity, bladder symptoms, tremor and overall improvements in quality of life. In some cases the improvement has been sufficient to transform lives."