Pubdate: Fri, 06 Jul 2001
Source: Globe and Mail (Canada)
Copyright: 2001, The Globe and Mail Company


As Canada moves ahead with legalization of marijuana for medicinal 
purposes, new research is casting doubt on its usefulness for pain relief.

Cannabinoids (cannabis in pill or injectable form) are no more effective 
than traditional painkillers, according to a study published in Friday's 
edition of the British Medical Journal.

Even when cannabinoids do work effectively, such as in controlling the 
nausea and vomiting related to chemotherapy, they have potentially serious 
side effects that should limit their use, a second group of researchers 

But Dr. Mary Lynch, director of research at the pain management unit of 
QEII Health Sciences Centre in Halifax, said the research should be 
interpreted cautiously and should not cast doubt on Canada's medicinal 
marijuana program.

"The bottom line is that there is not enough human research to draw any 
significant conclusions," she said in an interview. "Overall, I'm very 
enthusiastic about the future of cannabinoids, but there is a lot of work 
to be done in improving the drugs."

Dr. Lynch, who heads the Canadian Consortium for the Investigation of 
Cannabinoids in Human Therapeutics, praised Canada's approach to medicinal 
marijuana, and said it will help make the country a world leader in 
cannabinoids research.

"This country is taking a humane, reasonable, compassionate approach by 
approving the use of cannabis in specific conditions while we await the 
results of further research," she said. "And, at the same time, the 
government is funding cannabinoids research."

In the newly-published study, Dr. Fiona Campbell, a pain management 
consultant at Queen's Medical Centre in Nottingham, England, said that, at 
present, there is "insufficient evidence to support the introduction of 
cannabinoids into widespread clinical practice for pain management."

She said that, at best, a single dose of cannabis is the equivalent of 
taking 60 milligrams of codeine, "which rates poorly in relative efficacy." 
Further, the higher the dose, the greater the side effects.

In particular, Dr. Campbell and her team identified cannabis as having a 
depressant effect on the central nervous system, and adverse psychological 
effects such as panic attacks and paranoia. A synthetic version of the 
active ingredient in marijuana, THC (tetrahydrocannabinol), is used to 
manufacture cannabinoids in pill and injectable forms.

The research is not original, but an analysis of material that has already 
been published. The team looked at nine different trials in which 
cannabinoids were used on patients with cancer pain, chronic pain and 
post-operative pain. Dr. Campbell noted that only 222 patients were 
involved in all the studies combined, underlining the dearth of human 
research. None of the research involved patients who smoked cannabis 
because none was conducted.

The second study, also published in today's edition of the British Medical 
Journal, looked at the effectiveness of cannabis for controlling 
chemotherapy-induced nausea and vomiting.

Dr. Martin Tramer of the department of anesthesiology of the Hopitaux 
(CIRCUFLEX O) Universitaires in Geneva, analyzed the results of 30 
different studies.

He found that cannabinoids, in both pill and injectable form, worked very 
well for some patients. But the study also noted a number of troublesome 
side effects ranging from dizziness to low blood pressure.

Dr. Tramer said that patients treated with cannabinoids were five times 
more likely to discontinue treatment than those taking more traditional 
anti-nausea drugs.

"Potentially serious adverse effects, even when taken short term orally or 
intramuscularly, are likely to limit the widespread use," he said.

Again, none of the studies involved patients who smoked cannabis.

In Canada, only two cannabinoids have been approved as prescription drugs, 
both of them for patients with chemotherapy-related nausea.

In an editorial published in the journal, Dr. Eija Kalso, head of the pain 
clinic at Helsinki University Hospital, said that, at this time, 
cannabinoids "clearly lose the battle in both efficacy and safety with the 

But he too highlighted the potential of cannabinoids, and said much more 
research needs to be done on humans. Researchers are excited about the 
drugs because cannabinoids exist naturally in the body and they have shown 
dramatic results in animals -- including arresting tumour growth and 
controlling chronic pain.

Earlier this week, the federal government released the regulations related 
to medicinal use of marijuana. They require, among other things, that users 
obtain a photo identification and that doctors approve an application for 
use of cannabis.

The Canadian Medical Association objects strongly to the new legislation, 
saying that marijuana has not been subjected to the rigorous pre-market 
testing that other drugs must undergo.

Dr. Hugh Scully, past president of the CMA, said there is lack of 
comprehensive and credible scientific evidence on the benefits, and risks, 
of medicinal marijuana.

"We acknowledge the unique requirements of those individuals suffering from 
a terminal illness or chronic disease for which conventional therapies have 
not been effective," he said. "However, the CMA believes that it is 
premature for Health Canada to expand broadly the medicinal use of 
marijuana before there is adequate scientific support."

When the U.S. Institute of Medicine studied the pros and cons of medical 
marijuana use in 1999, it concluded that the "future of cannibinoid drugs 
lies not in smoked marijuana, but in chemically-defined drugs."

Supporters of medical marijuana dismissed those arguments, noting that 
there is much anecdotal evidence about the benefits of the drug and 
stressing that the regulations allow marijuana to be used only by people 
who are expected to die within 12 months; those with chronic medical 
conditions such as AIDS and multiple sclerosis; and those with serious 
medical conditions who can't find relief in any other way.
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