It's high time we make cannabis available for medical research

Herbal remedy: Marijuana’s potential pain-relief qualities should be more comprehensively studied. (John Vizcaino/Reuters)

Herbal remedy: Marijuana’s potential pain-relief qualities should be more comprehensively studied. (John Vizcaino/Reuters)

African regulatory authorities such as the South African Medicines Control Council should consider applications to approve medicinal cannabis for the treatment of chronic pain.

This is especially needed in the case of patients who are not responding well to conventional medication and where the use of medicinal cannabis may have a positive effect on its own or as an adjunct to existing medications.

But regulatory bodies must be guided by good evidence rather than by anecdotal reports or pressure from recreational users promoting a legalisation agenda.

Policymakers on the continent, and particularly in South Africa, need not be passive consumers of research conducted in Europe and the United States. Instead, our researchers should investigate the medicinal effects of cannabis in areas where the quality of the science to date is poor or where more research needs to be undertaken.

The Medical Research Council is well positioned to take a leading role as a conduit for local and international funding of, and support for, clinical trials of medicinal cannabis as well as other research in this vein.

Through the ages, many cultures have used cannabis as a medicine, but in the past 60 years prohibition has hampered research into its potential therapeutic effects.

Cannabis is the generic term for drugs produced from the plant Cannabis sativa. The principal active ingredient of cannabis is the cannabinoid, THC.
Chemicals derived directly from the cannabis plant or those manufactured synthetically in pill form, like nabilone and dronabinol, are known as cannabinoids.

Cannabidiol (CBD), another cannabinoid, is not psychoactive but is thought to have anti-anxiety and antipsychotic effects. The therapeutic effects of cannabis depend on the concentration of THC and the ratio of THC to CBD. Cannabinoids can be ingested orally, placed under the tongue, absorbed through the skin in patches or balms, smoked, inhaled, used as a suppository or drunk as a herbal tea.

Research has increased substantially over the past decade – but in the West, not in sub-Saharan Africa, despite the region’s good conditions for growing high-quality cannabis products outdoors.

In January the Medical Research Council released a policy brief on cannabinoids for medical use, in which we appraised a systematic review evaluating the medicinal use of cannabis, first published by Dr???Penny Whiting and colleagues in the Journal of the American Medical Association in June 2015.

The systematic review was commissioned by the Swiss federal office of public health and focused on randomised controlled studies evaluating cannabinoids for managing 10 conditions, including nausea and vomiting linked to chemotherapy, chronic pain, appetite stimulation in people with HIV, spasticity caused by multiple sclerosis or paraplegia, and glaucoma.

The authors identified 79 eligible randomised controlled studies and found evidence of a moderate quality to support the use of cannabinoids to treat chronic pain and to reduce spasticity in multiple sclerosis patients, but the clinical significance of the latter remains unclear. Evidence for a beneficial effect of cannabinoids in nausea and vomiting from chemotherapy was low, and similarly for weight gain in HIV patients. Safety concerns were raised, with some short-term adverse events reported, and the lack of long-term data from rigorous studies was noted.

Research to address these gaps will require making medical-grade cannabis available for research in various forms, and encouraging governments and international agencies to fund both preclinical research (cellular-level and animal studies) and human trials.

Support for research into medicinal cannabis must not be contrasted with a prohibition agenda against recreational use. Society has not forgone the use of morphine for fear of the recreational use of heroin. In fact, a study from the US published in 2015 in the Journal of Policy Analysis and Management suggests that medicinal cannabis policies reduce recreational cannabis consumption, except in states that permit dispensaries or home cultivation.

Before medicinal cannabis can be made more widely available, even for conditions such as chronic pain, where the evidence of benefit is strongest, policymakers will need to consider issues such as the safe supply and regulation of medicinal cannabis, the best routes for administration, cost-effectiveness and, at a later stage, issues such as selection criteria for eligible patients. Training of doctors, pharmacists and others in prescribing and administering medicinal cannabis and the instruction of patients in its use will also need to be developed.

  Professor Charles Parry is the director of the alcohol, tobacco and other drug research unit at the Medical Research Council. Professors Bronwyn Myers and Nandi Siegfried are chief specialist scientists in the same unit

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