IS THERE A ROLE FOR MARIJUANA IN MEDICAL PRACTICE?

NO

In its Marihuana Medical Access Regulations, Health Canada authorizes
physicians to prescribe dried cannabis, an unproven and potentially
dangerous substance, under the guise of medical treatment. The program is
intended to help patients with serious illnesses, such as HIV infection and
cancer, but severe arthritis is also listed as an indication. Surveys
confirm that chronic pain and arthritis are common reasons for medical
cannabis use.1 As analgesics, however, pharmaceutical cannabis products are
weaker and less well tolerated than opioids.2 While cannabis users testify
to its therapeutic benefits, they also commonly report pleasant
psychoactive effects that are easily confused with direct analgesia.

Safer Alternatives Available

The main active ingredient in marijuana is delta-9-tetrahydrocannabinol
(THC), but both an oral THC and a buccal spray of THC and cannabidiol are
available and are far safer than smoking dried cannabis. Cannabis smoke
contains many of the same carcinogens as tobacco, and case-control studies
suggest that cannabis smokers are at increased risk for prostate cancer and
for head and neck cancer.3 Cannabis smokers are also at increased risk for
bronchitis.4 Even if cannabis were vaporized and inhaled rather than
smoked, the rapid delivery of high THC doses increases the risk of
psychomotor impairment and addiction.

Risks Associated With Use

While many people smoke cannabis occasionally without obvious harm, regular
cannabis smoking can be dangerous. Cannabis use is a major risk factor for
psychosis and schizophrenia,5 aggravates psychotic symptoms,6 and might
have long-term cognitive effects.7 Adolescents who smoke cannabis have
higher rates of other substance use, school failure, criminal activity, and
suicidal thoughts.8 Cannabis impairs driving ability and so is a risk
factor for motor vehicle accidents.9 In utero cannabis exposure is
associated with attention deficit disorders, behavioural problems, and poor
academic performance in childhood.10

Health Canada states that "the average daily amount approved for over 90%
of patients … is 5 grams or less per day (5 to 10 joints)". Based on Health
Canada's calculations, 5 joints with 12.5% THC concentration will contain
approximately 400 mg of THC, or 20 times the maximum daily dose of oral
THC. A single oral 5-mg dose reaches a peak plasma THC level of 5 to 10
ng/mL within 2 to 4 hours, whereas a single joint reaches 200 to 300 ng/mL
within 6 to 9 minutes. This disparity puts patients at substantial risk for
adverse effects, including dependence and psychomotor impairment. Even at
therapeutic doses, symptoms of intoxication affected 40% of subjects in
trials of the THC and cannabidiol buccal spray, and 8% to 24% in the trials
of oral THC.

Legal Complications

Physicians are relatively safe from legal sanctions in cases of adverse
drug reactions as long as they have exercised due precaution. This
standard, however, will not protect physicians who prescribe an unapproved
drug, such as marijuana. The Canadian Medical Protective Association waiver
purportedly absolves physicians of legal responsibility for untoward events
related to cannabis prescribing, but it cannot protect physicians from
legal action brought by third-party victims.

Society Pays

From a public health perspective, the Health Canada program is
fundamentally unjust and harmful. The program diverts resources to an
unproven substance of uncertain efficacy with abuse liability, contributing
to the public's perception of cannabis as a harmless recreational product
with therapeutic benefits.

Forty-seven percent of 18- to 19-year-olds in Canada have smoked cannabis
in the past year, and 5% of Canadians report at least 1 concern related to
cannabis. Six thousand patients were treated for cannabis dependence in
Ontario in 2000, which likely represents a small fraction of those who need
help. As one author stated, "… the costs to society are continuing to mount
from past neglect of this continuing health problem."11

If legislators wish to decriminalize cannabis possession, they should do so
without disguising it as medical therapy. Smoked medical marijuana is
unnecessary and unsafe, especially in the doses allowed by Health Canada,
and it distracts physicians and the public from the widespread harm caused
by cannabis use and dependence.

References

1. Swift W, Gates P, Dillon P. Survey of Australians using cannabis for
medical purposes. Harm Reduct J 2005;2:18.

2. Campbell FA, Tramer MR, Carroll D, Reynolds DJ, Moore RA, McQuay HJ. Are
cannabinoids an effective and safe treatment option in the management of
pain? A qualitative systematic review. BMJ 2001;323(7303):13-6.

3. Hashibe M, Straif K, Tashkin DP, Morgenstern H, Greenland S, Zhang ZF.
Epidemiologic review of marijuana use and cancer risk. Alcohol
2005;35(3):265-75.

4. Tashkin DR, Baldwin GC, Sarafian T, Dubinett S, Roth MD. Respiratory and
immunologic consequences of marijuana smoking. J Clin Pharmacol 2002;42(11
Suppl):71S-81S.

5. Green AI, Tohen MF, Hamer RM, Strakowski SM, Lieberman JA, Glick I, et
al. First episode schizophrenia-related psychosis and substance use
disorders: acute response to olanzapine and haloperidol. Schizophr Res
2004;66(2-3):125-35.

6. Caspari D. Cannabis and schizophrenia: results of a follow-up study. Eur
Arch Psychiatry Clin Neurosci 1999;249(1):45-9.

7. Dafters RI, Hoshi R, Talbot AC. Contribution of cannabis and MDMA
("ecstasy") to cognitive changes in long-term polydrug users.
Psychopharmacology (Berl) 2004;173(3-4):405-10.

8. Fergusson DM, Horwood LJ, Swain-Campbell N. Cannabis use and
psychosocial adjustment in adolescence and young adulthood. Addiction
2002;97(9):1123-35.

9. Ramaekers JG, Berghaus G, van Laar M, Drummer OH. Dose related risk of
motor vehicle crashes after cannabis use. Drug Alcohol Depend
2004;73(2):109-19.

10. Goldschmidt L, Richardson GA, Cornelius MD, Day NL. Prenatal marijuana
and alcohol exposure and academic achievement at age 10. Neurotoxicol
Teratol 2004;26(4):521-32.

11. Dennis M, Babor TF, Roebuck MC, Donaldson J. Changing the focus: the
case for recognizing and treating cannabis use disorders. Addiction
2002;97(Suppl 1):4-15.

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KEY POINTS

Cannabis use has been associated with multiple medical problems,
including bronchitis, psychosis, and cognitive impairment.

The dose of dried cannabis recommended by Health Canada far exceeds the
recommended doses of approved products that contain THC and thereby puts
patients at risk for dependence and psychomotor impairment.

There is no good evidence for medical marijuana, and physicians might be
liable for prescribing an unapproved and unproven product.