Using cannabis for chronic pain is associated with a higher risk of heart rhythm disorders, according to new research.
Medical cannabis for chronic pain is a common combination, with a popular area of interest being the pain-relieving benefits it can provide. Medical cannabis comes in various forms depending on the THC and CBD levels. Dronabinol (high THC), cannabinoid (more THC than CBD), and cannabidiol (high CBD) can be prescribed in Denmark.
Study author Dr Nina Nouhravesh of Gentofte University Hospital, Denmark, said: “Chronic pain is a rising problem. According to Danish health authorities, 29% of Danish adults over 16 years of age reported chronic pain in 2017, up from 19% 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. Safety data are sparse, hence this study investigated the cardiovascular side effects of medical cannabis, and arrhythmias in particular, since heart rhythm disorders have previously been found in users of recreational cannabis.”
Prescriptions of cannabis in Denmark
The researchers identified 1.6 million patients with chronic pain in Denmark between 2018 and 2021. Within that, 4,931 patients claimed at least one prescription of cannabis for chronic pain. 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 monitored and compared.
The median age of participants was 60 years, and 63% were women. The study outlines the chronic pain conditions of medical cannabis users in Denmark. The researchers found that 17.8% of participants had cancer, 17.1% had arthritis, 14.9% had back pain, 9.8% had neurological diseases, 4.4% had headaches, 3% complicated fractures, and 33.1% had other diagnoses.
Risks of using cannabis for chronic pain
The absolute risk of new-onset arrhythmia was 0.86% in medical cannabis users compared with 0.49 in non-users, for a relative risk of 1.74. The researchers reported that the risk of the new-onset acute coronary syndrome and heart failure did not differ between the groups.
Dr Nouhravesh said: “Our study found that medical cannabis users had a 74% 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 was 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.”
She concluded: “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.”
