Therapeutic potential of medicinal marijuana: an educational primer for health care professionals

Abstract

With the proposed Canadian July 2018 legalization of marijuana through the Cannabis Act, a thorough critical analysis of the current trials on the efficacy of medicinal marijuana (MM) as a treatment option is necessary. This review is particularly important for primary care physicians whose patients may be interested in using MM as an alternative therapy. In response to increased interest in MM, Health Canada released a document in 2013 for general practitioners (GPs) as an educational tool on the efficacy of MM in treating some chronic and acute conditions. Although additional studies have filled in some of the gaps since the release of the Health Canada document, conflicting and inconclusive results continue to pose a challenge for physicians. This review aims to supplement the Health Canada document by providing physicians with a critical yet concise update on the recent advancements made regarding the efficacy of MM as a potential therapeutic option. An update to the literature of 2013 is important given the upcoming changes in legislation on the use of marijuana. Also, we briefly highlight the current recommendations provided by Canadian medical colleges on the parameters that need to be considered prior to authorizing MM use, routes of administration as well as a general overview of the endocannabinoid system as it pertains to cannabis. Lastly, we outline the appropriate medical conditions for which the authorization of MM may present as a practical alternative option in improving patient outcomes as well as individual considerations of which GPs should be mindful. The purpose of this paper is to offer physicians an educational tool that provides a necessary, evidence-based analysis of the therapeutic potential of MM and to ensure physicians are making decisions on the therapeutic use of MM in good faith.

Keywords: Access to Cannabis for Medical Purposes Regulations; Cannabis Act; Parkinson’s disease; Tourette’s syndrome; cannabis; endocannabinoid system; epilepsy; gastrointestinal disorders; medicinal marijuana; multiple sclerosis; pregnancy.

Figure 1

The endocannabinoid system and CB1/CB2 distribution. (A) The mechanism of action of the endocannabinoid system is depicted, with human endocannabinoids AEA or 2-AG binding to CB1 to initiate a signaling cascade through the release of neurotransmitters. THC is also able to bind to CB1, exerting its effects on the central nervous system and peripheral system. (B) Distribution of CB1 and CB2 in the body. CB1 is concentrated in the central and peripheral nervous systems. CB2 is more abundant in the immune system and, to a lesser degree, in the nervous system. Abbreviations: CB1/CB2, cannabinoid receptor 1/cannabinoid receptor 2; AEA, anandamide; 2-AG, 2-arachidonooylglycerol; THC, (−)-Δ⁹-trans-(6aR,10aR)-tetrahydrocannabinol.

Figure 2

The effects of cannabis on the central nervous system. Brain areas in the central nervous system (in black) and their physiological functions (in red) are listed alongside potential effects of THC and CBD (in blue and green), respectively. Abbreviations: THC, (−)-Δ⁹-trans-(6aR,10aR)-tetrahydrocannabinol; CBD, cannabidiol.