The battle to persuade GPs of the benefits of medicinal cannabis just got harder after the Faculty of Pain Medicine at the Australian and New Zealand College of Anaesthetists (ANZCA) and the International Association for the Study of Pain expressed doubts about its efficacy for chronic pain.

The Faculty of Pain Medicine at ANZCA claimed a lack of clinical trials meant there is no robust evidence to prove cannabinoids are effective in alleviating suffering.

As part of the global Choosing Wisely awareness campaign, ANZCA issued advice to GPs stating: “Do not prescribe currently available medicinal cannabis products to treat chronic non-cancer pain unless part of a registered clinical trial.”

ANZCA’s advice to GPs: “Do not prescribe currently available medicinal cannabis products to treat chronic non-cancer pain unless part of a registered clinical trial.”

It added: “The evidence available is either unsupportive of using cannabinoid products in chronic non-cancer pain, or is of such low quality that no valid scientific conclusion can be drawn.

“Cannabidiol-only formulations have not been the subject of a published randomised controlled trial (RCT) for pain indications, yet they are the most commonly prescribed type of product.”

“In addition, evidence of harms does exist, particularly in relation to sedative effects, interactions with other medications and neuropsychiatric effects (for products which contain tetrahydrocannabinol).

“Given the above, the clinical use of cannabinoid products cannot be ethically recommended outside a properly established and registered clinical trial environment until high-quality evidence for specific indications is published.”

The Dean of ANZCA’s pain medicine faculty Professor Michael Vagg told the Sydney Morning Herald medicinal cannabis products on the market “are not even close” to showing they are effective in treating patients with complex chronic pain.

He said: “The research available is either unsupportive of using cannabinoid products in chronic non-cancer pain or is of such low quality that no valid scientific conclusion can be drawn.”

“Substances like alcohol are more effective pound-for-pound, but we don’t have extended opening hours at Dan Murphy’s for pain patients.”

“Substances like alcohol are more effective pound-for-pound, but we don’t have extended opening hours at Dan Murphy’s for pain patients.”

Professor michael vagg

The move comes after the International Association for the Study of Pain released the findings of its review of medicinal cannabis research earlier this month.

It said its assessment of preclinical and clinical literature identified gaps in the rigor of study design and reporting.

“Gaps related to comprehensive understanding of the endocannabinoid system and cannabinoid pharmacology, including pharmacokinetics and drug formulation aspects.”

It added “important questions” remain about the long-term and short-term safety of cannabis and cannabinoids.

Professor Iain McGregor from the Lambert Initiative for Cannabinoid Therapeutics acknowledged the development of clinical evidence was in its infancy.

Lambert Initiative
Professor Iain McGregor from the Lambert Initiative

But he told the SMH: “This is a galloping horse heading off into the future with lots of patients already being prescribed medicinal cannabinoids and even more self-medicating.

“One of the things [ANZCA] has to reconcile is why would all these people continue to use a product that doesn’t help them?

“The TGA conducted its own review which concluded there is some evidence that it works but I agree, we need far more clinical trials in this space to give prescribers more confidence.”

“Let’s give medicinal cannabis the benefit of the doubt while the hundreds of clinical trials around the world build the evidence base for their use,” he added.

Medicinal Cannabis Industry Australia (MCIA) insisted there is evidence demonstrating the benefits of medicinal cannabis. It said it has supported the formation of the Medicinal Cannabis Health Advisory Council to inform and be the voice for patients and the community, and ensure access to education and training for prescribers.

It added: “MCIA believes that through a focus on balanced and evidence-based information, along with the industry adhering to high standards, there will be increased confidence in medicinal cannabis by patients, the medical/healthcare sector and community.”

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