“Evidence” for Medical Marijuana

Few months ago, I listened to CBC radio – The Current with Anna Maria Tremonti to discuss the controversial topic of using medical marijuana for PTSD (Post-traumatic stress disorder).  There was anecdotal evidence that it was helpful to some patients. But there were also safety concerns associated with long term use.  Even in my own practice of dementia patients with challenging behaviour, some have responded favourably to Nabilone (a synthetic version of marijuana) when everything else has failed.  But it was difficult to find any hard core evidence to support its use among the medical literature.  There are ongoing studies happening as we speak. But when medical marijuana has been around for ages, why is it difficult to find any “evidence” to support its use?

Here are some of the reasons for the lack of so-called “evidence” from my perspective:

  • Marijuana is not really a “drug” by the definition of pharmaceutical. Marijuana refers to the crude product of Cannibis, a plant source that contains more than 100 compounds. We have extracted few specific ones such as THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol) with known pharmaceutical properties found to be helpful but their composition may differ among different plants, different sources and different packaging. It would be very challenging to study one specific type of plant source because it cannot be generalized to offer similar benefits from other sources.
  • It is difficult to conduct clinical trials with marijuna. Because it does not fall under the category of pharmaceutical, it does not need to follow the same regulations as other pharmaceuticals. But if we are to treat it similar to other pharmaceuticals, then it needs to comply with regulations such as GMP (good manufacturer practice) and GCP (good clinical practice) under the same category as pharmaceutical. To recognize any health claims, it needs to have clinical evidence from placebo-controlled randomized studies. These are expensive to conduct and many “manufacturers” of marijuana may lack the experience and the resources to carry out any study of such rigour and design.
  • There are many conditions for which marijuana is claimed to be useful. Marijuana has been reported to potentially offer benefits in a number of medical conditions including pain (neuropathic pain), spasticity, seizure control, chemotherapy induced nausea and vomiting and weight loss in AIDS/HIV population and many others.  But each specific health claim needs its own individual study. It would require some assertive recruitment effort to enroll individuals of sufficient sample size to carry out any good quality study.

But does that mean we are starting from ground zero? I don’t think so. We have many anecdotal experiences from various places and various sources. If we can openly collect data from these users, gather information about their purpose of use, perceived usefulness, we may be able to gather some basic demographic data to understand and appreciate where to go next with the data analysis and ponder about future studies. We need to start somewhere, although where we start may not be ideal but we need to start from somewhere.  If we expect to conduct clinical studies on marijuana the same way we conduct clinical studies for statins, then we are setting ourselves up for failure.   Perhaps in the process of legalizing marijuana in Canada, we will implement some policies to support some mandatory  ongoing research activities.  By doing so, we may be able to set up the basic infrastructure for gathering “evidence” in medical marijuana.


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My name is Cynthia Leung and I am a practicing pharmacist in Kingston Ontario, Canada. This blog is for me to share my ideas, opinions and perspectives on how medications are used in our health care system. Note that these posts are my own opinions and do not represent the opinions of my current or former employers and / or organizations that I may belong to. Any possible case scenarios described in my posts would be modified to maintain patient confidentiality. This blog is not a platform for professional advise for patients or health care providers and the content is not meant to support any clinical decisions or replace professional opinions. Also the images are either taken or created by the author, or adapted with permission. I hope you will enjoy reading my posts!

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