Doctors warn on rush to prescribe cannabis

Australia is “navigating uncharted waters with pharmaceutical grade cannabinoids” and doctors need to be cautious about prescribing them, according to an editorial in Medical Journal of Australia.

The article, written by Newcastle University’s Jennifer Martin and two colleagues in the name of the Royal Australian College of Physicians (RACP), says evidence for the effectiveness of medical cannabis is limited.

Medical research standards based on clinical data and review have not yet been met, the authors write, and until they are doctors should be wary of how they respond to “calls for compassionate access”. Until appropriate trials have been completed, the RACP says, doctors should adopt a “precautionary approach” to prescribing, “in the knowledge that substantial harms may be experienced by many individuals using these products”.

Martin and her co-authors add that a rush to prescribe medical marijuana – available in some circumstances through the Therapeutic Goods Administration’s Special Access Scheme – risks jeopardising the eventual accumulation of high quality information.

“Widespread prescription will likely remove incentives to invest in critical research necessary to understand these potential therapeutic agents and their effectiveness in treating a range of conditions in the long term,” they write.

In this possibility they see an echo of an earlier example of a prescribing trend running ahead of the evidence. Treatment of persistent non-cancer pain with opioids, they say, began with little evidence that it was an effective strategy. The result was “an epidemic of overdose deaths and poor pain outcomes, resulting in ongoing suffering”.

For these reasons, they conclude, doctors must carefully engage with patients to explain a cautious approach to prescribing cannabinoids. There is an obligation to provide evidence-based information about treatment options – and doing that “is the most compassionate course we can currently take”.

In a second editorial in the same issue, John Lawson of the Sydney Children’s Hospital and three colleagues review the case for using cannabis products to treat severe childhood epilepsy – a strategy that medical marijuana advocates claim is well supported by evidence.

Lawson and his co-authors again strike a note of caution. Evidence for the use of cannabis in treating epilepsy is “limited but growing”, they state, but at this stage is based on only one randomised double-blind trial. There is evidence that cannabis works as an anticonvulsant, but the mechanism by which it does so remains unclear.

They state that studies into the effects of cannabis on children with epilepsy – especially a severe form known as Dravet’s syndrome – “represent an important area of research for our patients”. The editorial concludes by calling for more high quality trials to investigate long-term safety, efficacy and dosages, so that the results may “guide medical decision making and the political and legal framework”.

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