The health and psychological consequences of cannabis use - chapter 8

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8. The therapeutic effects of cannabinoids

8.10 The politics of therapeutic cannabinoid use

A puzzle in the field of cannabinoid therapeutics is that despite the positive appraisal of the therapeutic potential of cannabinoids as anti-emetics and anti-glaucoma agents, they have not been widely used. Nor has the detailed type of clinical pharmacological research been undertaken on optimal methods of clinical use in those areas where the cannabinoids do have therapeutic potential (e.g. as anti-emetics). Part of the reason for this is that research on the therapeutic use of these compounds has become a casualty of the debate in the United States about the legal status of cannabis. This emerges from an inspection of the arguments recently advanced for and against an application to the United States Drug Enforcement Agency to change the status of marijuana under the Controlled Substances Act, 1970 from a schedule I drug which has no accepted medical use to a schedule II drug which has an accepted medical use (see Randall, 1988, 1989, 1990).

The proponents of rescheduling (National Organisation for the Reform of Marijuana Laws, Alliance for Cannabis Therapeutics, and Cannabis Corporation of America) have argued that marijuana should be available for medical use, as smoking is the most effective mode of delivering THC for some therapeutic purposes. The opponents of rescheduling (Drug Enforcement Agency, International Chiefs of Police, The National Federation of Parents for a Drug Free Youth) have countered that marijuana has no therapeutic use, since its few uses are better met, either by other more effective drugs which do not have the psychoactive effects of THC, or by the oral delivery of synthetic cannabinoids. They have been supported by medical researchers and practitioners who argue for the therapeutic superiority of pharmaceutically pure drugs which can be given in defined doses (e.g. Levitt, 1986; Mechoulam, 1988; Nahas, 1984).

Medical researchers who have supported the rescheduling of marijuana (e.g. Grinspoon and Bakalar, 1993; Merritt, 1988; Mikuriya, 1990; Morgan, 1990; Weil, 1988) have argued that smoked cannabis is superior to oral synthetic cannabinoids in effectiveness and has a lower risk of producing unwanted psychoactive side-effects. Apart from the unsuitability of oral medication for patients who are vomiting, their main arguments in favour of smoking as a route of THC administration are similar to the reasons recreational users often give for preferring smoking to the oral use of cannabis. The greater bioavailability of THC via smoking produces a more dependable therapeutic effect, which is more easily controlled because users have a greater ability to titrate their dose, and hence, to maximise the desired effects while minimising the unpleasant effects. An additional argument sometimes used is that there may be other cannabinoids present in the crude plant product which modulate the undesired side effects, including the unpleasant dysphoric effects of THC (Grinspoon and Bakalar, 1993). There is also suggestive evidence that smoked cannabis is as effective as oral THC, and may be preferred by patients because of the greater control they have over dose (Chang et al, 1979).

Opponents of marijuana rescheduling argue that the undesirable psychoactive side effects of THC disqualify it from widespread medical use, whatever the route of administration. Most also believe that smoking is a medically unacceptable route of administration of THC because it is unsuitable for very young and very old patients, there is a risk of infection with micro-organisms which may contaminate the plant material, and there is the danger that chronic smoke inhalation may produce or exacerbate bronchitis, and expose the user to carcinogens (e.g. Levitt, 1986; Mechoulam, 1988; Nahas, 1984).

he proponents of rescheduling respond that none of these are compelling reasons for rejecting smoked marijuana for therapeutic purposes until more potent and specific therapeutic cannabinoids have been identified and synthesised. Smoking, they point out, would not be a compulsory method of administration; only an option for those patients who preferred it, as would the use of cannabinoids if patients did not like their psychoactive effects. The contamination of micro-organisms reported with blackmarket cannabis can be overcome, they argue, by standardising dose and using an anti-microbial treatment, as has been done by National Institute on Drug Abuse (NIDA) in preparing cannabis cigarettes for research (Randall, 1988). The risks of bronchitis and respiratory tract cancers, it is argued, are small with the intermittent and time-limited smoking of cannabis that would occur in the course of cancer chemotherapy. In any case, proponents of rescheduling argue, it is probably a risk that many patients with a life-threatening illness may be prepared to run, as shown by their preparedness to take highly toxic and carcinogenic anti-cancer agents.

Weil (1988) has argued that some opponents have used double standards in appraising the risks of marijuana smoking. According to Weil, the most common psychoactive effects of marijuana (euphoria, somnolence and dysphoria) are minor, non-life-threatening and self-limiting effects that can be easily managed, and are of much less severity than the side effects of many other widely-used therapeutic drugs. Medical witnesses for the government, he claims, "do not contrast marijuana's supposed adverse effects with the known adverse effects of drugs routinely prescribed for the treatment of conditions like cancer, glaucoma and multiple sclerosis. Instead, ... [they] compare marijuana to some abstract, unobtainable standard of perfection" (p437).

Merritt (1988) has made a similar point in criticising the arguments raised against the therapeutic use of marijuana to manage glaucoma: " ... each drug family used in glaucoma therapy is capable of producing a lethal response, even when properly prescribed and used .. [p470] [but] these drugs are all deemed "safe" for use in glaucoma therapy .. because their adverse consequences are considered less threatening to the patient than blindness" (p472). Yet marijuana is excluded from therapeutic use because of a possible risk of cancer from long-term daily smoking. "I cannot see", observes Merritt, "how an alleged case of marijuana-induced lung cancer which results in death is significantly different in result from an acute adverse reaction to a myotic drug which results in respiratory failure, except, of course, that the patient with cancer is likely to outlive the patient who is unable to draw in a breath of air" (p474).

Although the debate about the rescheduling of marijuana has been ostensibly about the safety and efficacy of marijuana use, it has been driven by the debate about the legal status of recreational marijuana use. For example, some of the groups advocating the therapeutic use of cannabis have also been proponents of cannabis legalisation (e.g. NORML), thereby fuelling the fears of opponents of cannabis use that success in the campaign for marihuana rescheduling will be the thin edge of a wedge to legalise cannabis. Other proponents of legalisation (e.g. Grinspoon and Bakalar, 1993) have turned this reasoning around, by arguing for the legalisation of cannabis as a way of making cannabis available for therapeutic purposes.

On the other side of the argument are those opponents of marijuana use who fear that the admission that marijuana, or any of its constituents, may have a therapeutic use will send the "wrong message" to youth. This has led to the denial that cannabinoids have any therapeutic effects, and to attempts to stifle all scientific inquiry into any such effects. For example, Mr Bernstein representing the National Federation of Parents for a Drug Free Youth had the following to say in his summing up against Rescheduling marijuana before Judge Young (1989):

"If marijuana were to be rescheduled to Schedule II, what kind of message are we sending to a nation that is engaged in a battle for it's very survival because of epidemic drug abuse? ... will not the message be that marijuana is good for cancer, good for glaucoma, good for spasticity and a host of other illnesses? Now to all of this who are the most vulnerable? The answer is, of course, our young people. Their reaction will be that if it is good for all of these things, it can't be bad for me. We then have another youngster trying marijuana, the gateway drug and probably starting down the road that leads to nowhere but destruction" (in Randall, 1989, p395).

It is unfortunate that a connection has been forged between the debates about the legal status of cannabis as a recreational drug and the use of cannabinoids for therapeutic use. Any such connection is spurious, since there is a world of difference between the use of controlled doses of a purified drug under medical supervision and the recreational use of crude preparations of a drug. In a rational world, linical decisions about whether to use pure cannabinoid drugs should not be abrogated because crude forms of the drug may be abused by those who use it recreationally. As a community we do not allow this type of thinking to deny us the use of opiates for analgesia. Nor should it be used to deny access to any therapeutic uses of cannabinoids derivatives that may be revealed by pharmacological research.