Viewpoints: Medicinal cannabis paradigms, part 2

The evidence is not quite there, and the risks are yet to be defined

For this edition of Viewpoints, we provide contrasting perspectives from two medical professionals on the merits of medicinal cannabis. It’s a timely issue considering the current Bill before Parliament that would amend the Misuse of Drugs Act to improving access for people to possess and use cannabis.

Dr Sam McBride counters that the evidence isn’t all that compelling and that the risks are not yet fully clear – despite the naïve naturalist claims of some of its proponents.. See Part 1: "Medicinal cannabis seems to work, let’s get on and explore its uses".

The debate over medicinal cannabis, like many relating to prohibited drugs, is polarised and prone to hyperbole. Medical professionals have been criticised for being “prejudiced”: reluctant to embrace the perceived benefits, narrow in their thinking and subject to vested interests. This is countered by the argument that cannabis is a “complex slush of chemicals” lacking evidence for use and proposed by those prone to naturalistic fallacy: a naïve belief that natural products are inherently good. This debate confuses the prohibited status of cannabis as an excuse for trying to force a product that largely fails to conform to medical standards into a clinical framework.

Cannabis has been used medicinally for thousands of years, with many of the described uses similar to those for which it is promoted today. Morphine, the main active ingredient of opium, was isolated in the 19th century, allowing provision of a purified, quantified product and development of synthetic medications. Development of cannabinoid products, however, remains in its infancy. Prohibition and lack of the motivating intellectual property rights have contributed to lack of knowledge regarding the body’s endocannabinoid system and development of specific medications. The current expanding knowledge of this system rarely finds its way into the medical curriculum. Medical students will learn more about the harms of cannabis related to recreational use.

These factors have contributed to cannabis as medicine being a consumer-driven – not doctor-driven – phenomenon. The tension between a consumer and medical paradigm is illustrated by the dismay expressed in the Journal of the American Medical Association at the way medicinal cannabis had been introduced to various North American States through “low quality scientific evidence, anecdotal reports, individual testimonials, legislative inquiries, and public opinion” (De Souza, 2015).

Medical commentators have argued that the debate serves as a Trojan horse by which legalisation can be smuggled through society’s bastions – sanitising the moral overtones related to recreational drug use. Certainly, frameworks for medicinal cannabis preceded legalisation in Canada, Colorado and California. Here, the medical profession became disingenuous gatekeepers for a variety of cannabis products whose relationship to medicines was often spurious (medicinal cannabis gummy bears?!) and provided the framework for a ready commercial market. The conjoined nature of much of the industry catering for both recreational and medical use is rightly treated with suspicion.

Recent New Zealand legislation illustrates how access to medicinal cannabis appears as an effort to sidestep the awkward issue of prohibition. While allowing those expected to die within a year to use cannabis without fear of prosecution may be compassionate, as a proposed amendment to the Misuse of Drugs Act, it is practically and philosophically fraught. Medically, it relies on the ability of doctors to accurately make such judgements and raises issues of equity. (Why exclude those suffering from debilitating illnesses or longer timeframes, and where does the threshold for deciding sit?) Doctors are being delegated the duty of deciding who can worthily access cannabis while politicians deride them for lack of leadership on the issue.

There is also a yawning chasm between the claims made for medicinal cannabis and those supported in medical literature with no clear unifying biological premise. Recent extensive summaries of the evidence for cannabinoids as medicine have concluded that there is evidence of moderate quality to support use in chronic pain and spasticity with less to support use in a handful of other indications including nausea and vomiting due to chemotherapy, weight gain in HIV infection, sleep disorders and Tourette syndrome. With improved medications for nausea and the ability to halt the progression of HIV, the need for alternatives seems less obvious. The evidence that doctors expect to rely upon for decision making stands in marked contrast to the claims made for cannabis by advocates, which seem to cover every medical complaint possible including curing cancer. Surveys of people using cannabis for “medicinal” reasons indicate that, while use in the context of pain is high, so too is use where there are no diagnosable symptoms.

Clinical frameworks rely upon a reproducible medication and consistent dosing along with evidence of efficacy and licensed indications. Only one medication meeting these standards is licensed in New Zealand: nabiximols (trade name Sativex). Pharmaceutical grade products in New Zealand can also be accessed, though they are unable to be licensed as medications. The Ministry of Health requires monitoring of use and processes to reduce diversion of these products. This need is inconsistent with probable risks and not required for some medications where these risks are greater.

Insufficient evidence, products that sit outside usual processes, highly invested consumers and a potentially lucrative market mean that a niche medicinal cannabis service appears likely to develop. This will further distance medicinal cannabis from mainstream medicine and an evidence-based approach.

Regardless of the ability to access standardised cannabinoid products, debate often centres around plant material – another example of the confluence of medicinal and recreational use. Overseas surveys indicate a preference for botanical cannabis even when alternatives exist. Doctors with expectations of standardised medications are faced with a material that is subject to environmental influences in production, degrades over time with altered properties and is often smoked. Proposed regimes giving medical approval for patients to grow their own similarly confuses the boundaries between prohibition and medical sanction.

Compromise is needed. It is certain that cannabinoids have medical potential, but the limits and risks have yet to be defined and are unlikely to fulfil the promise advocates hope for. There is a need for doctors to clarify the role of medicinal cannabinoids while juggling the reality that products conforming to typical medicinal standards are likely to be several years away – while the demand for informed access was yesterday. Medical education needs to include the role of the endocannabinoid system and the potential role of cannabinoids as a medicine, and research and development of medical cannabinoids guidelines should be prioritised in universities and hospitals.

Likewise, medicine should be allowed to continue without having to compromise practice because society remains conflicted over prohibition. It is this, not doctors, that is at the heart of the issue.

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See Viewpoints: Medicinal cannabis paradigms, part 1: "Medicinal cannabis seems to work, let’s get on and explore its uses"