Over the past year several patients have asked me to prescribe medical marijuana for them. They have sought treatment for a variety of conditions and I haven’t suspected any of them of wanting an easy route to recreational cannabis. Nevertheless, I’ve refused every request.
To understand why requires that we look at three things: evidence, the act of prescribing and politics.
Most patients are surprised to learn that we have little research on medical marijuana. A systematic review of Cannabinoids for Medical Use published in June found 79 studies but judged that only four were at low risk of bias. Furthermore, the evidence gathered in the study fails to meet the usual threshold to approve pharmaceuticals.
The report found that there are only two conditions where we have at least moderate quality evidence of medical marijuana’s benefit: chronic pain and persistent muscle spasticity from neurological injury.
In contrast, the authors could find no better than low quality evidence that cannabis products help with:
• Nausea and vomiting due to chemotherapy
• Weight gain in HIV patients
• Tics due to Tourette Syndrome
Lastly, they were unable to identify any evidence that marijuana is better than placebo for depression, anxiety, Crohn’s disease, Parkinson’s disease or glaucoma.
At the same time, cannabinoids have many common side effects. These include dizziness, fatigue, confusion, hallucination and nausea and vomiting (which cannabis is supposed to treat, not cause). As an older person who once mistakenly consumed a marijuana-laced brownie confided: “That’s what people do for fun? Some fun!”
The bottom line on research to date demonstrates that the only two situations where we can be reasonably confident that medical marijuana will help are when patients suffer from chronic pain or constant muscle contractions.
OK, you say. But why won’t you prescribe medical marijuana in at least those two situations?
To answer that we need to take a brief detour into pharmacology.
When a doctor prescribes any treatment we need to know how to choose a dose. The maximum dose is the level at which the treatment becomes toxic or where additional amounts don’t add to the desired effect. The minimum dose has to be high enough to expect at least some measurable benefit for the patient. The dosages between the minimum and maximum are the “therapeutic dose range” for the treatment.
In centuries past, treatments were derived from plants. As time passed, local “apothecaries” prepared botanical extracts with highly variable concentrations of the active ingredients and unknown measure of unwanted other components. With advances in chemistry in the late 1800s, treatments became manufactured products with greater purity and precise measures of the active ingredients.
The result is what we recognize as modern prescribing. A doctor provides a prescription with the name of the specific drug, the dose (measured by weight), the frequency of dosing and the total quantity. If a patient were to receive a prescription with only a drug type and a daily dosing amount – e.g. blood pressure medication, 1-3 mg daily – that patient would have understandable concerns about the competence of the prescriber.
And yet, such imprecise prescribing is exactly what doctors are being asked to do with medical marijuana. There is no attempt to purify the product to its active ingredient(s), no control of the concentration of those ingredients, no standard dose size (what’s a “joint” in mg?) and no frequency of dosing. You call that “medical”?
However, though I won’t prescribe medical marijuana I will prescribe cannabinoids in the form of nabilone, a legal synthetic drug in pill form. As with all modern pharmaceuticals, it comes in a specific dose and regulation-approved dosing quantities and timing. Some of my patients with chronic pain get considerable relief from using the drug.
Nevertheless, recent research has started to uncover not just immediate adverse effects of cannabinoids but also worrisome long-term effects. The developing human brain is particularly vulnerable, which is why both the American Academy of Pediatrics (AAP) and American College of Obstetricians and Gynecologists (ACOG) have released policy statements this year that warn about the dangers of exposing fetuses and anyone under 21 years to marijuana.
But the evidence of harm doesn’t end when we enter adulthood. A 2014 study that looked at the brains of long-term marijuana users found significant structural and functional changes. And though not yet evaluated in humans, a study published in July showed that when rats ingest marijuana but stop prior to conceiving they nevertheless pass on adverse genetic changes to their offspring.
Finally, let’s look at the politics behind medical marijuana.
Most people will overlook the fact that the AAP policy statement includes a recommendation to decriminalize marijuana use by youth and young adults because the effects of prosecution and conviction are inappropriately harsh. An editorial that accompanies the systematic review cited above goes further and gets to what I think is the heart of the matter: it asserts that medical marijuana is just a strategic step by commercial interests seeking the ability to sell for recreational use.
That doesn’t mean that I’m opposed to recreational use. If we publicize the risks, require that products contain and disclose measured doses, limit access to people under 21 and strictly punish impaired driving, then it’s difficult to justify refusing marijuana the same standing as alcohol. Doing so will also provide new tax revenue and close down a criminal black market.
Which is precisely what a growing majority of North Americans has concluded. That has started the move toward legalizing marijuana as a controlled recreational substance, beginning in four states with several more and Canada considering the same.
And prudent legalization, not placing doctors in the role of interim gatekeeper under the ruse of “medical marijuana”, is the proper outcome of the emerging evidence and our evolving social thinking.