IS THERE A ROLE FOR MARIJUANA IN MEDICAL PRACTICE?

YES

Crude preparations of herbal cannabis have been used for thousands of years
to treat many symptoms, including pain, spasms, and nausea.1 Preparations
historically included extracts of roots, leaves, and flowering heads but
were not commercially standardized or characterized. Modern pharmacology
has identified the principal psychoactive ingredient of cannabis as
delta-9-tetrahydrocannabinol; specific cannabinoid receptors have been
identified in the central and peripheral nervous system as well as in
immune cells, endothelial tissue, and other visceral organs.2 Animal
studies have confirmed that many of the effects of cannabis in humanbeings
have solid neurophysiologic bases, particularly with respect to pain
control.3 The cannabinoid system is, therefore, a major target for drug
development.4

History of Medical Cannabis Policy in Canada

In 1999 the Court of Appeal for Ontario ruled that it was unconstitutional
to enforce the rule of law with respect to cannabis.5 Since 2001, the
Marihuana Medical Access Regulations (MMAR) have made cannabis possession
legal for authorized patients in Canada. Since July 2005 the streamlined
MMAR application requires that physicians sign a form confirming the
diagnosis, the symptoms, the fact that prior treatments have been tried or
considered, that the use of cannabis has been discussed, and that cannabis
is not an approved drug.6

There are 2 main categories of complexes recognized under the MMAR: those
requiring approval from family physicians and those requiring approval from
both family physicians and specialists. For the second category, family
physicians must discuss the case with a specialist; whose name and the date
of consultation, but not signature, are required. Amending this process
appears to have increased the number of applications. As of September 2006,
1492 persons were authorized to possess medical marijuana and 917
physicians had supported applications under this program.7

Herbal cannabis, cultivated by Prairie Plant Systems Inc under licence to
Health Canada, is distributed to authorized patients for $5/g. This herbal
cannabis is cultivated under controlled conditions, is free of
contaminants, and is irradiated to destroy pathogenic microorganisms. It is
delivered as a milled herb with 10 mm particles and moisture content of
15%. The potency is standardized at 12% 2.0% delta-9-tetrahydrocannabinol.8

Cannabis and Family Physicians

What do family physicians need to know about the MMAR? First, there is a
legal means by which patients can obtain quality-controlled cannabis for
medical use. Second, physicians do not "prescribe" cannabis under this
approach but instead support a patient's application for authorization to
possess the drug. This process reduces the risk of prosecution for patients
whose cannabis use is part of a therapeutic approach. Third, medical
cannabis use can be documented and monitored as part of standard care.

Prescribed cannabinoids offer an alternative to herbal cannabis and should
be considered in all cases where cannabis is discussed. Inhaled
cannabinoids have the potential pharmacokinetic advantages of bypassing the
first-pass effect of hepatic metabolism, of rapid onset of action, and of
easy titration. Risks include irritation of the upper airways, cognitive
effects of central cannabinoid activity, and stimulation of reward mechanisms.

Considerations

Advocates for medical marijuana are often involved in political action to
change policy. For every placard-carrying marijuana activist, however, many
more silent sufferers have turned to cannabis where all else has failed.
These patients might be afraid to discuss cannabis with their doctor and
might not be aware that they have other legal and safe options. Physicians
will formulate their own moral and scientific positions based on available
evidence. Cannabis has not yet been formally evaluated in clinical trials,
but safety and efficacy studies are under way and further studies should be
designed and conducted. Without such trials it is premature to consider
prescribing cannabis, but based on what is known of a drug that has been
around for thousands of years, based on the safety data generated from 2
generations of recreational users, and based on the mechanism of action of
cannabinoids, it is reasonable for family physicians to become more
familiar with cannabis. Its undignified position as a drug of abuse with no
known medical value deserves to be reconsidered.

Dr Ware is Assistant Professor in Anaesthesia and Family Medicine at McGill
University in Montreal, Que, Associate Medical Director of the MUHC Pain
Centre, and a practising pain physician. Dr Ware receives salary support
from the Fonds de la recherche en sante Quebec and holds grants from the
Canadian Institutes of Health Research.

References

1. Mechoulam R. The pharmacohistory of Cannabis sativa. In: Mechoulam R,
editor. Cannabinoids as therapeutic agents. Boca Raton, Fla: CRC Press;
1986. p. 1-19.

2. Pertwee RG, Ross RA. Cannabinoid receptors and their ligands.
Prostaglandins Leukot Essent Fatty Acids 2002;66(2-3):101-21.

3. Meng ID, Manning BH, Martin WJ, Fields HL. An analgesia circuit
activated by cannabinoids. Nature 1998;395:381-3.

4. Bernadette H. Cannabinoid therapeutics: high hopes for the future. Drug
Discov Today 2005;10(7):459-62.

5. Court of Appeals for Ontario. R. v Parker. Toronto, Ont: Court of
Appeals for Ontario; 2000. Available from: http://www.ontariocourts.on.ca/decisions/OntarioCourtsSearch_VOpenFile.cfm?serverFilePath=d%3A%5Cusers%5Contario%20courts%5Cwww%5Cdecisions%5C2000%5Cjuly%5Cparker%2Ehtm

6. Marihuana Medical Access Regulations. (2001). Canada Gazette, Part II
(reference July 4, 2001-SOR 2001-227). Available from: http://www.hc-sc.gc.ca/dhp-mps/alt_formats/hecs-sesc/pdf/marihuana/marihuana-reg_e.pdf
Accessed 2005 Oct 1.

7. Health Canada. Marihuana for Medical Purposes. Statistics (September 1,
2006). Ottawa, Ont: Health Canada; 2005. Available from:
www.hc-sc.gc.ca/dhp-mps/marihuana/stat/2006/sept_e.html. Accessed 2006 Oct 28.

8. Health Canada. Health Canada's marihuana supply. Ottawa, Ont: Health
Canada; 2005. Available from:
http://www.hc-sc.gc.ca/dhp-mps/marihuana/supply-approvis/index_e.html.
Accessed 2005 Oct 1.

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KEY POINTS

There is solid scientific rationale for therapeutic use of cannabis.

Pharmaceutical cannabinoid preparations should always be considered.

Mechanisms exist in Canada for herbal cannabis to to be used legally.

Ongoing research and education regarding cannabis is needed.