Cannabis for Chronic Pain: Increased Arrhythmia Risk?

According to a study published today (Thursday) in the European Heart Journal, people who use medical cannabis for chronic pain have a slightly increased risk of arrhythmia. Arrhythmia occurs when the heart beats too slowly, too rapidly, or in an irregular pattern. It include conditions such as atrial fibrillation.

Cannabis use for recreational purposes has been related to cardiovascular illness, but there has been little research on the side effects of medical cannabis.

According to the researchers, the new study is significant because an increasing number of countries now allow medical cannabis as a treatment for chronic pain.

Dr. Anders Holt of Copenhagen University Hospital – Herlev and Gentofte in Denmark led the study. It contained information on 5,391 Danish patients who were prescribed cannabis for chronic pain. This includes persons suffering from muscular, joint, or bone pain, cancer patients, and those suffering from nerve discomfort. The researchers compared this group to 26,941 patients who had chronic pain but were not being treated with cannabis.

According to the statistics, patients who received medical cannabis had a 0.8% chance of developing arrhythmia that required monitoring and maybe treatment within 180 days of obtaining cannabis. This risk was more than double that of patients with chronic pain who did not use cannabis. When researchers looked at the first year of treatment, the risk gap between the two groups had shrunk.

Patients consuming cannabis who were 60 or older, as well as those who had already been diagnosed with cancer or cardiometabolic disease, such as heart disease, stroke, or diabetes, had the highest incidence of arrhythmia.

The study found no link between medical cannabis use and an increased risk of acute coronary syndrome, which includes a heart attack, unstable angina, stroke, or heart failure.

Medical cannabis is now allowed as a treatment for chronic pain in 38 US states as well as several countries in Europe – such as Spain, Portugal, the Netherlands and the UK – and elsewhere around the world. This means more and more doctors will find themselves prescribing cannabis, despite a lack of evidence on its side effects.

I don’t think this research should make patients with chronic pain refrain from trying medical cannabis if other treatment has been inadequate. However, these results do suggest some improved monitoring may be advisable initially, especially in patients who are already at increased risk of cardiovascular disease.”

Dr. Anders Holt from Copenhagen University Hospital – Herlev and Gentofte in Denmark

Researchers say this is the first nationwide study of its kind investigating the cardiovascular effects of medical cannabis for chronic pain. However, they caution that this is an observational study. Dr. Holt explained: “Despite our best efforts to make a balanced comparison, it can never be assumed that patients prescribed medical cannabis do not differ from patients not prescribed medical cannabis, and this could influence the results.”

He added: “We need much more research in this area. Before concluding anything, results from this study should be replicated in other countries and settings. It would also be interesting to understand if there are any links between long-term cannabis use and heart failure, stroke, or acute coronary syndrome. This would be an important area to clarify since chronic pain can persist for many years.”

Prof. Robert L. Page of the University of Colorado, USA, wrote in an accompanying editorial, “Close pharmacovigilance of cannabis, as well as its safety and efficacy, have been limited by decades of worldwide illegality and the ongoing classification of cannabis as a Schedule 1 controlled substance in the United States.” Nonetheless, as cannabis has become more decriminalized and legalized around the world, the link between cannabis exposure and incident cardiovascular events has emerged as an essential safety signal.

“Therapeutically, these findings suggest that medical cannabis may not be a ‘one-size-fits-all’ therapeutic option for certain medical conditions and should be contextualized based on patient comorbidities and potential vulnerability to side effects.

“Cannabis is typically referred to as recreational and ‘medical’ or ‘medicinal’. This latter terminology has come under scrutiny as it includes both phytochemical-derived cannabis products and also prescription cannabinoids approved in the EU. Additionally, the term ‘medical’ implies that the product may have some clinical monitoring along with safety and efficacy data, which is far from true with cannabis. To this end, I would argue that ‘cannabis for therapeutic use’ would be a more appropriate terminology rather than ‘medical’.”