By Pat Anson, PNN Editors

Pain management experts around the world are becoming more vocal about the growing use of medical marijuana as a treatment for chronic pain, saying there is little evidence to support the use of cannabis as an analgesic.

Today the Faculty of Pain Medicine at the Australian and New Zealand College of Anaesthetists (ANZCA) released new guidance urging doctors not to prescribe medical cannabis for patients with chronic, non-cancer pain unless they are enrolled in a clinical trial.

“Until there are results from high-quality, unbiased clinical trials which establish the effectiveness and safety of medicinal cannabis in treating chronic pain, the Faculty of Pain Medicine does not believe cannabinoid products should be prescribed,” Mick Vagg, MD, Dean of the Faculty of Pain Medicine, said in a statement.  

“We want to highlight to healthcare providers that currently available medical cannabis products are not even close at this stage to showing that they deserve a place in the management of the complex patients who suffer from ongoing pain. We believe clinicians will welcome this clear guidance.”

ANZCA is a professional society for nearly 8,000 anesthesiologists and pain management specialists in Australia and New Zealand, and sets standards for pain medicine in both countries.

Australia and New Zealand have some of the highest rates of cannabis consumption in the world. But New Zealand only allows medical cannabis for terminally ill patients, while Australia requires a prescription for cannabis that is often difficult to obtain.

About one if five Australians live with chronic pain.   

“By far the most common reason for the use of medicinal cannabis in this country is chronic pain − however there is a critical lack of evidence that it provides a consistent benefit for any type of chronic non-cancer pain, especially compared to the treatments we already strive to provide in pain clinics,” Vagg 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. Cannabidiol-only formulations have never been the subject of a published randomised controlled trial for chronic pain treatment, yet they are the most commonly prescribed type of cannabis product.”

Vagg also said research is lacking in how cannabinoids react with pharmaceutical drugs, particularly in relation to their sedative and psychiatric side effects.

‘Hypothesis’ of Analgesia

ANZCA’s new guidance came just days after the International Association for the Study of Pain (IASP) released a position statement saying it could not endorse the use of cannabinoids to treat pain. IASP said there were preliminary studies supporting the “hypothesis of cannabinoid analgesia,” but not enough to overcome the lack of evidence on the safety and efficacy of cannabinoids.

“While IASP cannot endorse the general use of cannabinoids for treatment of pain at this time, we do not wish to dismiss the lived experiences of people with pain who have found benefit from their use,” said Andrew Rice, MD, chair of IASP’s Presidential Task Force on Cannabis and Cannabinoid Analgesia.

“This is not a door closing on the topic, but rather a call for more rigorous and robust research to better understand any potential benefits and harms related to the possible use of medical cannabis, cannabis-based medicines and synthetic cannabinoids for pain relief, and to ensure the safety of patients and the public through regulatory standards and safeguards.”

Rice said IASP was concerned that laws allowing the use of medical marijuana were being adopted without the same rigor and regulatory procedures that are followed for pharmaceutical products. Patients who self-treat their pain with cannabis are also at risk, according to Rice, because their doctors often don’t know about their cannabis use.  

“IASP is also calling for the delivery of a comprehensive research agenda. Priorities include identifying patients with pain who may receive the most benefit from cannabis or cannabinoids, and who may be at risk of the most harm,” said former IASP president Lars Arendt-Nielsen, MD, who co-chaired the Cannabis Task Force.

Supporters of medical cannabis dispute the contention that there is inadequate evidence about the use of cannabis for pain.

“These recommendations are political, not scientific. Several peer-reviewed trials have concluded that inhaled cannabis is safe and effective for treating various types of pain, in particular neuropathic pain,” Paul Armentano, Deputy Director of NORML, said in an email to PNN.

Armentano cited a 2017 study from the U.S. National Academy of Sciences, which found “conclusive or substantial evidence” that cannabis is an effective treatment for chronic pain.

“In the real world, the therapeutic use of cannabis is rising among chronic pain patients, many of whom are substituting it in place of opioids. In jurisdictions where cannabis is legally available, chronic pain is the most qualifying condition among medical cannabis patients enrolled in state-specific access programs. To willfully ignore these data is indicative that political considerations, rather than scientific considerations, influenced this group’s decision,” Armentano said.