Prescribed cannabis linked with ‘small risk’ of heart problems

Medicinal cannabis, prescribed for chronic pain, has been linked to a modest increase in the risk of heart rhythm disorders.

New research presented at European Society of Cardiology Congress 2022 has found cannabis prescribed for chronic pain to be associated with an elevated risk of heart rhythm disorders.

While heart rhythm disorders have previously been identified in recreational cannabis consumers, little data is available yet on the cardiovascular effects of medicinal cannabis.

Investigators at Gentofte University Hospital, Denmark aimed to shine some light on any potential safety risks, particularly that of cardiovascular arrhythmias from cannabis which is prescribed for chronic pain.

Medical cannabis comes in various formulations depending on tetrahydrocannabinol (THC) and cannabidiol (CBD) levels. 

Dronabinol (high THC), cannabinoid (more THC than CBD), and cannabidiol (high CBD) can be prescribed legally in Denmark. The drug can be inhaled, eaten, or sprayed in the mouth.

The researchers identified a total of 1.6 million patients diagnosed with chronic pain in Denmark between 2018 and 2021. 

Of those, 4,931 patients claimed at least one prescription of cannabis (dronabinol per cent, cannabinoids 46 per cent, cannabidiol 25 per cent). 

Each user was matched by age, sex and pain diagnosis to five non-users with chronic pain who acted as controls. Users and controls were followed for 180 days and their risks of new cardiovascular conditions were compared.

The median age of participants was 60 years and 63 per cent were women. 

The study reports, for the first time, the chronic pain conditions of medical cannabis users in Denmark. These include cancer, arthritis, back pain, neurological diseases, headaches and complicated fractures. Around a third of participants were classed as having other diagnoses (mostly unspecified chronic pain).

The absolute risk of new-onset arrhythmia was 0.86 per cent in medical cannabis users compared with 0.49 per cent in non-users, for a relative risk of 1.74. 

The risks of new-onset acute coronary syndrome and heart failure did not differ between the two groups. 

The results were similar for each chronic pain condition and each type of medical cannabis.

READ MORE: Cannabis and heart health – potential risk or protective agent?

Study author Dr Nina Nouhravesh said: “Chronic pain is a rising problem. According to Danish health authorities, 29 per cent of Danish adults over 16 years of age reported chronic pain in 2017, up from 19 per cent in 2000. 

“Medical cannabis was approved in January 2018 on a trial basis in Denmark, meaning that physicians can prescribe it for chronic pain if all other measures, including opioids, have proven insufficient.”

She continued: “Our study found that medical cannabis users had a 74 per cent higher risk of heart rhythm disorders compared with non-users; however, the absolute risk difference was modest. 

“It should be noted that a higher proportion of those in the cannabis group were taking other pain medications, namely non-steroidal anti-inflammatory drugs (NSAIDs), opioids and anti-epileptics, and we cannot rule out that this might explain the greater likelihood of arrhythmias.”

In conclusion, Dr Nina Nouhravesh commented: “Since medical cannabis is a relatively new drug for a large market of patients with chronic pain, it is important to investigate and report serious side effects. This study indicates that there may be a previously unreported risk of arrhythmias following medical cannabis use. 

“Even though the absolute risk difference is small, both patients and physicians should have as much information as possible when weighing up the pros and cons of any treatment.”

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