Earlier this week the Faculty of Pain Medicine at the Australian and New Zealand College of Anaesthetists (ANZCA) published guidance for health practitioners recommending against the prescription of medicinal cannabis for the treatment of chronic non-cancer pain (CNCP).

The recommendation is based on the current lack of high-quality evidence demonstrating medicinal cannabis products are effective for treating CNCP conditions.

The fact that much more research needs to be conducted is indisputable. As is the fact that the current evidence – though promising – is still a far cry from the conventional data physicians are used to relying on.

Cannabiz editor-at-large Rhys Cohen

Unfortunately, Dr Michael Vagg (Dean of the Faculty of Pain Medicine) in an article in The Conversation, went much further than this. And in doing so he made some arguments that do not stand up to logical scrutiny.

Dr Vagg’s article is structured around busting three “myths” about medicinal cannabis. These are:

  1. Evidence shows cannabis products are effective for chronic pain
  2. Cannabis products should be provided as a ‘last resort’
  3. Medicinal cannabis may help with the opioid crisis

Let’s interrogate some of the claims he makes in each of those sections.

1) Evidence shows cannabis products are effective for chronic pain

Several placebo-controlled randomised controlled trials (RCTs) have investigated the potential of THC-containing cannabis medicines to treat chronic pain and found that medicinal cannabis can, in some cases, be effective. Based on the clinical research we have so far, the Therapeutic Goods Administration (TGA) argues that:

“We can be moderately confident that CNCP patients receiving medicinal cannabis are more likely to achieve 30% and 50% reductions in pain and to report a reduction in pain ratings than patients given a placebo.”

The point here is not ‘my source is better than your source’, but that Dr Vagg is not disagreeing with the TGA. He does not say “there is no evidence”, he says “there is not enough evidence”.

Given there is enough evidence (though far from conclusive) for the TGA to be “moderately confident” that medicinal cannabis can work in CNCP, the more useful question to ask is “is there enough evidence, given the circumstances?”. Which brings me to my next point.

2) Cannabis products should be provided as a ‘last resort’

Around 600,000 Australians already use cannabis for medicinal purposes. The idea that restricting access to prescription cannabis would prevent the medicinal use of cannabis in Australia is a childish fantasy.

This magical thinking is captured by Dr Vagg’s comments in a recent Sydney Morning Herald article, where he comments:

“It is such an amateur mistake to backfill this evidence gap now when this product is already being used. There should have been rigorous work to prove it’s effective and safe and then put it on the market and continue to monitor its effectiveness.”

I guess we should issue a medicine recall for the ~200,000kg of cannabis that has been consumed in Australia every year since the 1980s? This is a deeply flawed line of argument.

Approximately 50,000 Australians have been prescribed a cannabis medicine by a doctor so far. That number will likely double over the next 12 months, and the vast majority of prescriptions will be for some kind of CNCP condition.

ANZCA are entitled to offer their scientific assessment of the evidence regarding medicinal cannabis and CNCP. And they believe there is not enough published evidence to be confident that medicinal cannabis can treat CNCP conditions.

There is published evidence to suggest otherwise, and groups such as the TGA have come to different conclusions based on the same information. I am not a scientist or a doctor but from the many conversations I have had with patients, clinicians and scientists, I know that some people can (and do) use cannabis to successfully manage their CNCP conditions.

And there are many doctors, including pain specialists (some of whom are members of the College), who have examined the evidence, listened to their patients, prescribed medicinal cannabis, and seen their patients benefit from it.

But even if you were a medical doctor who had no confidence that medicinal cannabis might help treat your patient’s CNCP condition, there are reasons you might consider prescribing regardless.

It takes courage and compassion for GPs to go out on a limb and consider medicinal cannabis

First, there is a harm minimisation argument. Many patients are already using cannabis. If they have no intention of ceasing use because they are experiencing a benefit (whether a drug or placebo effect), objecting to medicinal cannabis is only going to ensure they keep buying unregulated, unknown products from drug dealers.

This puts their health at risk and exposes them to potential criminal sanctions. It also means doctors have no oversight regarding which compounds they are consuming and at what doses. If you are concerned about adverse effects and drug-drug interactions, this kind of information is clinically relevant.

Second, there is a risk-based argument. Patients may have already found several first-line treatments to be ineffective. The next treatment may be a somewhat risky procedure such as a spinal fusion. Prescription medicinal cannabis products pose very few health risks compared to benzodiazepines, let alone opioids or unintended outcomes from surgery. There is still a small chance that medicinal cannabis might have some kind of an effect, and if it doesn’t work, there is no harm done.

Third, there is a compassionate argument. Patients may have reached the end of their interventional options. Perhaps they are doing the best they can with psycho-social therapies, but their quality of life is still severely impacted. On the off-chance that medicinal cannabis might reduce their suffering even slightly – whether by improving their pain or sleep or mood – you might consider trialling it.

One of Dr Vagg’s arguments against prescribing medicinal cannabis products is that they are expensive. In fact, he claims medicinal cannabis products are “among the most expensive pharmaceutical products available to chronic pain patients”.

Medicinal cannabis products are not currently covered by the Pharmaceutical Benefits Scheme (PBS). And product costs are a challenge for many patients. On average, Australians pay ~$400 per month for their prescribed medicinal cannabis products. Dr Vagg should know this as he cited the Q1 2020 FreshLeaf Analytics report where these figures are estimated.

This is far from being the most expensive category of pharmaceutical products available to chronic pain patients. For example, the new migraine drug Erenumab was recently rejected by the Pharmaceutical Benefits Advisory Committee. Dr Vagg drew attention to the issue of Erenumab in a previous Conversation article where he called for greater PBS coverage of expensive pain medications. Without PBS subsidy, patients are expected to pay upwards of $800 per month to the drug sponsor.

This is not to down-play the seriousness of affordability, or to engage in ‘whataboutism’. Medicinal cannabis is more expensive than it should be. The point is that this issue is not helped by needless hyperbole, especially when more accurate figures are readily available in documents that have already been cited by the author. Accidental or deliberate, this omission makes it seem like Dr Vagg has an unscientific axe to grind with medicinal cannabis.

3) Medicinal cannabis may help with the opioid crisis

Dr Vagg argues (quite rightly) that we should be prioritising specialist pain clinics to reduce opioid-related harms for CNCP patients. I am not at all suggesting that every CNCP patient can manage their condition using cannabis alone. But the efficacy of these clinics does not negate the potential utility of medicinal cannabis.

The more relevant link to draw between pain clinics and medicinal cannabis is this one: the median number of days an Australian has to wait to be seen by a public pain clinic is 110 days. Some people have been waiting for these services for several years.

We should urgently expand public funding for these services, something I know Dr Vagg has been advocating for some time. But we should not pretend that the desperation of people living with CNCP can be easily addressed in the absence of broader health system changes, especially for those in rural and regional Australia.

Medicinal cannabis may provide some relief, or even just some hope, for people who are forced to wait for these clinics, and for those who do not experience sufficient relief from their symptoms despite clinic services.

Dr Vagg has this to say about the possible link between medicinal cannabis and the opioid epidemic:

“Proponents of medicinal cannabis have suggested it may hold promise as a potential solution to this problem. While this idea has some appeal, the balance of the evidence points the other way.”

The possible link between cannabis and reductions in opioid-related harms and deaths is an emerging one. To my knowledge, there are no large placebo-controlled RCTs that have investigated the potential impact of cannabis use on opioid use or harms.

There are many doctors… who have examined the evidence, listened to their patients, prescribed medicinal cannabis, and seen their patients benefit from it.

Some of the most compelling evidence of this possible link so far (in humans) comes from retrospective population-level studies within the United States, of which there have been several in recent years. These studies have generally found a statistically significant correlation between cannabis becoming legally available, and subsequent – often very large – reductions in opioid prescriptions and overdose deaths. A causal link has yet to be proven.

Dr Vagg refers to this article as the justification for why opioid-sparing has “some appeal”. The article is a fairly comprehensive summary of many studies which have found a link between cannabis use and reductions in opioid use and harms. It also includes a few studies which did not find such a link, and explains the emerging nature of the evidence and that more research needs to be done before strong conclusions can be made.

The example that Dr Vagg uses to suggest that the “balance of evidence points the other way” is a single Australian study published in 2018. In this study, 1,514 participants on prescription opiates completed an annual survey about their pain, opioid use, and cannabis use over four years. By the end of the study, 295 of them had used non-prescription cannabis (at some time, of some kind, at some dose) to help treat their CNCP. The study found that people who ended up using cannabis experienced more pain and anxiety, with no reduction in their opioid medications, than those who did not.

It seems obvious to me that people who are experiencing increasing pain and anxiety would be more likely to seek out illegal cannabis, and more likely to continue using opioids, than those who are managing comparatively better. And this study was not designed in such a way as to draw the conclusion that Dr Vagg makes. It was unable to find evidence of an opioid sparing effect, which is very different from proving that one does not exist.

But what I find disingenuous is that Dr Vagg goes to great lengths to argue that under no circumstances should anyone prescribe cannabis for CNCP because only a few, relatively small placebo-controlled clinical trials have been conducted, and the evidence is moderate at best.

Yet in the same article, he is prepared to cite a single observational study of ~300 people using illicit cannabis of unknown composition, concentration or dose, which is unable to determine causality, and say “the balance of evidence” points towards cannabis having no impact on opiate use.

In conclusion

I am sure many pain specialists are frustrated with what I can only assume is a constant stream of patients asking them about medicinal cannabis. At the end of the day, as Dr Vagg says, clinical decisions are theirs to make in collaboration with their patients. Without the normal drug approval data doctors have come to expect, it must take some courage and compassion (perhaps Dr Vagg and colleagues would say recklessness) to go out on a limb and consider medicinal cannabis.

With or without conventional evidence, Australians will continue using cannabis to treat their pain. And if their specialist won’t consider it, there are plenty of private cannabis clinics that will. Leaving aside disputes over evidence and efficacy, if for no other reason than to reduce harms and prevent the fragmentation of care, I dearly hope the Australian and New Zealand College of Anaesthetists changes its position on this increasingly serious issue.

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2 Comments

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  1. Congratulations on these thoughtful, balanced comments. What matters most in prescribing is for benefits>harm. As harm of cannabis is modest, especially if regulated, odds are good for benefits to exceed harm. Medicine was too slow to recognise that often harm>benefit for opioids in chronic non cancer pain. Medicinal cannabis should be safe, available, affordable. We are still a long way from that.

  2. I agree with many of your comments Rhys. Unfortunately none of the RCTs conducted with cannabis in pain would meet the stringent IMMPACT requirements for clinical trials for analgesic medications because of strong placebo responses found in pain medicine. I don’t condemn patients for trying medicinal cannabis because of the relatively poor response to any analgesic medicine.