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Written by

Dr Mark A Ware Dr Mark A Ware is director of clinical research, Alan Edwards Pain Management Unit, McGill University Health Centre, Montreal, Canada

Cannabis and pain management: what does the future have in store?

Published 9 August 2016

Cannabinoids have considerable potential to treat neuropathic pain and other chronic pain states, but the development of cannabis-derived treatments is hampered by a number of factors, writes Dr Mark A Ware

Key learning points

  • There is reasonable evidence to suggest that cannabinoid therapies can relieve chronic pain, and neuropathic pain in particular, with an acceptable safety profile.
  • Stigma and the illegal status of cannabis are barriers to the more widespread development of cannabinoid drugs by the pharmaceutical industry.

The herb Cannabis sativa, and the analgesic properties of its constituent compounds (called phytocannabinoids), continues to perplex and challenge the decision-making and communication skills of clinicians worldwide. Healthcare professionals across the globe struggle to reconcile their increasing appreciation and awareness of powerful and robust endocannabinoid-mediated analgesic mechanisms with a distinct lack of sophisticated and available cannabinoid drugs and delivery systems, as well as a shortage of classical clinical research evidence.

In the meantime, patients who have either discovered that cannabis ‘reaches the parts other drugs cannot reach’, or are curious to know what all the fuss is about, are banging down the doors of pain clinics to get access. This is a very curious state of affairs for the 21st century.

The current impasse has a lot to do with the illegal status of cannabis, which has made cannabis research and drug development very difficult. In the absence of evidence, and in the face of considerable stigma yet also public sympathy, patients have turned to the courts or the ballot box to demand access. To a large extent, they have won the day, forcing the creation of medical cannabis access programmes before the conventional drug approval process has caught up. For example, many US states have legalised medical use of cannabis. How then is the pain clinician to make sense of all this?

Efficacy of cannabinoids

It is important to realise that there is little doubt now that phytocannabinoids have analgesic properties, even in inhaled form. Several systematic reviews have now concluded that there is moderate evidence that cannabis is a reasonable treatment option for chronic pain, and in particular for neuropathic pain.1–3 This is in spite of the short duration and modest effect sizes noted in these studies.3 In addition, safety studies have found that cannabinoids have a reasonable safety profile,4–6 and are not associated with significant tolerance to their analgesic effects.6

The challenge for the clinician is to teach the patient that more is not better. Higher doses of cannabinoids, in particular the psychoactive delta-9-tetrahydrocannabinol (THC), usually mean more side-effects, whereas analgesic effects of inhaled cannabinoids have been noted with single doses of 15–25mg of herbal material.7,8

Attempts to avoid the plant and focus on tapping into the endocannabinoid system have not been very successful. For example, blocking the enzyme fatty acid amide hydrolase (FAAH), which breaks down endogenous anandamide, has failed in phase II clinical trials.9 The recent death of a subject taking an FAAH inhibitor in a phase I trial in France has effectively put a stop to further exploration of this mechanism.10

So, for the time being, we are left with herbal extracts and crude delivery systems to relieve our patients’ suffering. There is considerable promise for cannabinoids, even in these basic forms, to reduce opioid requirements and reduce opioid-overdose mortality. We need to get out of our pharmaceutical comfort zone and learn how to use these compounds wisely and safely, and to recognise that the synthetic pharmaceutical industry is unlikely to be of much help in the near future. We need to work with our patients, expand our vocabularies and advocate for quality control, standardised delivery systems and more data. It will be a shame on us all if, five years from now, we are still having the same debate.

  • Dr Mark A Ware is director of clinical research, Alan Edwards Pain Management Unit, McGill University Health Centre, Montreal, Canada