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Can I have medical cannabis on PBS doctor?

13 December 2019 - Dr Simon Curtis

I’ve been asked this question twice in the last month. Once by a 70 year old patient who has taken up smoking weed to control her neuropathic pain, let’s call her ‘Rachel’. And the other a young man aged 26 (Clive) who is smoking cannabis to help control his chronic anxiety. Unsurprisingly in Australia the answer is no on both counts. It is not on the Register of Therapeutic Goods and, therefore, will have to be, in all cases, supplied through the Special Access Scheme (SAS). Who can apply through the SAS is dependent on State or Territory laws.

For severe treatment resistant epilepsy the TGA recommendation is “in the absence of strong evidence for dosing and specific preparations of cannabis or cannabinoids in epilepsy treatment, it is recommended that, should the treating physician elect to initiate medicinal cannabis therapy in epilepsy patients, patients should be re-evaluated after 12 weeks for evidence of response to treatment”. For the rare childhood epilepsy syndromes Lennox-Gestaut and Dravet there is no separate guidance from the TGA.

The vast majority of patients who want medical cannabis are like Rachel and Clive. They have disabling long-term conditions which we treat with blunt tools, often with disappointing results. These conditions generally need a holistic, non-drug, long-term approach for successful management. One of the unintended consequences of the legalisation of medical cannabis has been an increase in hope and expectation for patients that it may be a solution to their problem. One that for many patients appears to be more attractive and ‘natural’ (Rachel tells me, with a wink in her eye, that her weed is one of her 5 a day) than the licensed and evidence-based ‘chemicals’ we often prescribe.

Living with chronic pain, anxiety or neurological disease is hard, a daily struggle, so this increase in hope is totally understandable. However, the evidence is currently not there to substantiate its’ use in non-cancer pain as a first-line option. There is some weak evidence that as adjuvant therapy there is some benefit but also significant side effects.

What about Rachel and her hope for a treatment to control her chronic pain?

Managing these expectations for GPs is hard, but cannabis can be applied for through the TGA. This should not be first-line but only when all other therapeutic options have been exhausted. However, recent systematic review PAIN 2018 for chronic non-cancer pain found that cannabis and cannabinoids were just not very effective. To achieve a 30% reduction in pain compared to placebo, the NNT were 25 and there was no evidence they were better than a placebo to produce a ≥ 50% reduction in pain. The numbers needed to harm were 6. Similarly last year for neuropathic pain a Cochrane systematic review 2018 found a lack of good evidence that any cannabis-based product works for chronic neuropathic pain.

And Clive, who is smoking cannabis to help his symptoms of chronic anxiety?

A systematic review of trials of cannabinoids for the treatment of long-term mental health disorders has just been published by Lancet Neurology. Th concluded there was no evidence that medical cannabis improved the symptoms of depression, ADHD or PTSD and it was associated with an increase in adverse events. There was a small improvement in anxiety symptoms in some trials but the quality of the evidence was described as ‘very low quality’.

A valid criticism of these systematic reviews is the ‘rubbish in, rubbish out argument’ as most of the studies are small, low-quality and looking at a heterogenous range of products and trials. It is fair to say that we have a lack of evidence, rather than evidence of lack, at this stage. Furthermore, all these studies have been short-term so concerns regarding dependence and long-term effects on cognition and mental health have not been addressed.

So, where does this leave us and our patients?

GPs are expert at managing patient’s hopes and expectations, and also at working with patients within their own belief systems. Neither Rachel nor Clive will be impressed by the recent systematic reviews. The fact it seems to help them is all the evidence they need. But these publications will help us to help our patients at least make informed choices pending further research. There is genuine hope that from this research evidence-based effective treatments may emerge. But the current ‘opioid crisis’ we are seeing in chronic non-cancer pain should make us exercise great caution before recommending any cannabis-based products ahead of a supportive evidence base.

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This article was originally published on the NB Medical Education Hot Topics Blog. Edited for Australia by Dr Joanna Bruce.

Dr Simon Curtis
Dr Simon Curtis

Simon is the Medical Director NB Medical Education, an NHS GP in Oxford and Hon Senior Clinical Lecturer in General Practice, Oxford University.

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