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Major Studies of Drugs and Drug Policy
Canadian Senate Special Committee on Illegal Drugs
Volume I - General Orientation

Chapter 9 - Use of marijuana for therapeutic purposes 

Contemporary knowledge  

Two questions strike us relevant here. The first is whether marijuana in fact has the therapeutic effects that have been ascribed to it traditionally and more recently in the personal stories of people suffering from chronic pain and other conditions. If those benefits are real, the second question, altogether different and based on different criteria, is whether marijuana should be considered a drug.


Therapeutic uses

Knowledge of the mechanics of cannabinoids and the endogenous cannabinoid system allows a number of observations to be made. Generally, and bearing in mind what was written in Chapter 5, the action of cannabinoids can be described as follows:

 […]the overall effect is that of a cellular inhibition rather than cellular activation. It settles down nerve firing through a number of different types of reactions, primarily through changes that lead to changes in the flow of ion channels, which changes the firing behaviour of the cell which then changes how it communicates with other cells down the line.

Opening of potassium channels with decreased cell firing and closing of calcium channels with decreased release of neurotransmitters or overall cellular inhibition, which quiets things down. Those could have major therapeutic implications in certain clinical situations, such as pain and spasticity. They have implications in settling down nerve firing within pain conducting systems. [1][14]

More specifically, cannabinoids act on various neurophysiological systems associated with pain, either alone or in combination with the endogenous opiate system.[2][15] Cannabinoids affect the release of serotonin, which is itself associated with different types of pain, migraines in particular. Anandamide and other cannabinoid antagonists block the release of serotonin and ketanserin, both of which are linked to migraines, suggesting the potential effect of THC. Cannabinoids are also related to the dopamine system, which has been linked with migraines and other types of pain. Further, cannabinoids inhibit prostaglandin, producing an anti-inflammatory effect. Some studies have shown that THC is in that sense a more powerful analgesic than aspirin or even cortisone. Interacting with the endogenous opioid systems, cannabinoids increase the production of beta-endorphins, which reduce the effect of migraines. According to some studies, THC may have greater therapeutic potential than morphine, either because the applications would be more specific in some cases, because in other cases morphine aggravates some symptoms, or because THC lacks the sedative properties of morphine. Moreover, THC may have an antinociceptive effect on the periaqueductal grey. Finally, THC acts as a glutamate blocker and thereby reduces muscle and inflammatory pain.

Italian researchers Nicolodi, Sicuteri and colleagues have recently elucidated the role of NMDA antagonists in eliminating hyperalgesia in migraine, chronic daily headaches, fibromyalgia, and possibly other mechanisms of chronic pain. Gabapentin and ketamine were suggested as tools to block this system and provide amelioration. Given the above observations and relationships, it is logical that prolonged use of THC prophylactically may exert similar benefits, as was espoused in cures of chronic daily headache in the 19th century with regular use of extract of Indian hemp. [3][16]

In real terms, these mechanisms mean that cannabinoids can be beneficial in a number of situations that involve pain, but not pain alone The following are foremost among them.

               Emisis: Nausea is a common condition in cancer patients undergoing chemotherapy. As a result of a series of clinical trials involving people who reported using marijuana to relieve their vomiting, synthetic dranobinol (or Marinol) and nabilone (or Cesamet) were developed and tested primarily in the United States and Great Britain beginning in the 1970s. According to Dr. Lynch, “cannabinoids are thought to be modest antiemetics. There are more effective antiemetic agents available. However, because antiemetics work through a number of different mechanisms and because often we need to be able to target more than one mechanism to treat nausea and vomiting, cannabinoids are looking like they may be useful because they may offer us another option.”[4][17]


··               Cachexia: A significant number of people with AIDS/HIV suffer progressive anorexia coupled with weight loss. Some studies show that cannabinoids can help improve their situation, mainly because THC increases appetite. Some reservations have been voiced regarding the harmful effects of smoked THC on the immune system: “More recently, Nieman et al (1993) have shown that cigarette smoking by HIV seropositive individuals is associated with a more rapid development of AIDS because smoking increases the incidence of Pneumocystis carinii pneumonia (PCP).”[5][18] Others, however, have come to different conclusions: “A particular public health concern surrounds cannabis effects on HIV/AIDS. Four studies among others may reduce related concern. Kaslow et al. (1989) demonstrated no evidence that cannabis accelerated immunodeficiency parameters in HIV‑positive patients. DiFranco et al. (1996) ascertained no acceleration of HIV to full‑blown AIDS in cannabis smokers. Whitfield, Bechtel and Starich (1997) observed no deleterious effects of cannabis usage in HIV/AIDS patients, even those with the lowest CD4 counts. Finally, Abrams et al. (2000) studied the effects of cannabis smoking on HIV‑positive patients on protease inhibitor drugs in a prospective randomized, partially blinded placebo-controlled trial. No adverse effects on CD4 counts were observed secondary to cannabis.”[6][19]


··               Glaucoma: Glaucoma is an eye disease in which intraocular pressure builds because the fluid in the eye has difficulty draining and which leads to gradual destruction of the ocular nerves. Marijuana, in particular paste made from cannabis leaves, has been used to reduce intraocular pressure since ancient times, as we saw in the previous section. Recent studies suggest that marijuana – including smoked marijuana – helps reduce the effects of glaucoma. However, there have been some reservations because of some of the side effects of smoking marijuana (redness and drying of the eyes). In a case study by Russo et al. on four patients who smoked marijuana, one patient with glaucoma stated in court that the marijuana saved her sight.


··               Spasms and convulsions: The anticonvulsive properties of marijuana that help control epileptic seizures and the antispasm properties that are useful in treating multiple sclerosis are well known in Canada; marijuana use for epilepsy gave rise to the Ontario Court of Appeal decision in Parker. Smoked marijuana and synthetic cannabinoids appears to be effective in controlling these conditions. However, because of the bioavailability of synthetic compounds (between 20% and 30%) and their delayed effect relative to smoked marijuana, patients seem to prefer smoking.


··               Pain: The analgesic effects of marijuana in easing different types of pain have also been known since ancient times. We described the analgesic effect of marijuana above. More importantly, marijuana has specific effects on some types of pain that opiates do not.


[1][14]  Dr. Mary Lynch, Director, Canadian Consortium for the Investigation of Cannabinoids, Professor, Dalhousie University, testimony before the Special Senate Committee on Illegal Drugs, Senate of Canada, first session of the thirty-seventh Parliament, June 11, 2001, Issue 4, page 49.

[2][15]  The following information is taken primarily from Russo, op. cit., Hartel, C.R., “Therapeutic Uses of Cannabis and Cannabinoids”, in Kalant, H. (ed.), The Health Effects of Cannabis, Toronto: Addiction Research Foundation, and INSERM (2001), op. cit.

[3][16]  Russo, op. cit., page 365.

[4][17]  Dr. Mary Lynch, op. cit., page 52.

[5][18]  R.D. Hartel, op. cit., page 465.

[6][19]  Russo, E.B., et al. (2002), “Chronic cannabis use in the compassionate investigational new drug program: An examination of benefits and adverse effects of legal clinical cannabis”, Journal of Cannabis Therapeutics, Vol. 2, No. 1, page 45.

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