Medical cannabis for chronic pain treatment linked to arrhythmia risk

Medical cannabis for chronic pain treatment linked to arrhythmia risk

January 11, 2024

4 min read

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Key takeaways:

  • Medical cannabis use was tied to elevated risk for first-time arrhythmia in patients with chronic pain.
  • Risk was similar regardless of CBD, THC and combination CBD/THC use.

Medical cannabis use for chronic pain may confer increased risk for de novo arrhythmia compared with nonuse or other treatments for chronic pain, researchers in Denmark reported.

There was no observed relationship between cannabis use and risk for ACS, according to the findings published in the European Heart Journal.

Graphical depiction of data presented in article

Medical cannabis use was tied to elevated risk for first-time arrhythmia in patients with chronic pain.
Data were derived from Holt A, et al. Eur Heart J. 2024;doi:10.1093/eurheartj/ehad834.

“Despite following a huge cohort of almost 2 million patients with chronic pain for up to 4 years, just 5,391 patients were prescribed medical cannabis in the period; thus, medical cannabis does not seem to be widely used by physicians nor requested by patients yet in Denmark,” Anders Holt, MD, cardiologist at Copenhagen University Hospital — Herlev and Gentofte in Denmark, told Healio. “The median age of medical cannabis initiators was fairly low at 59 years. Short-term risk of arrhythmia was significantly elevated in patients prescribed medical cannabis compared with matched control patients, but the absolute risk increase was modest at 0.4% in the first 180 days.”

Anders Holt

Holt and colleagues conducted the present study to understand the relationship between first-time arrhythmia — defined as atrial fibrillation/flutter, conduction disorders, paroxysmal tachycardias and ventricular arrhythmias — and ACS and medical cannabis use for chronic pain.

Using nationwide Danish registers, the researcher identified 5,391 patients with chronic pain who initiated medical cannabis use from 2018 to 2021 (median age, 59 years; 63% women) and age-and sex-matched them 1:5 to 26,941 control patients also with chronic pain diagnosis but use of different pain medication.

The most prevalent chronic pain was musculoskeletal, followed by unspecified chronic pain, neurological pain and cancer.

CBD and/or THC and arrhythmia risk

Among patients on medical cannabis, 24% used CBD, 29% used combination CBD/THC and 47% used THC alone.

Different pain medications used by the control arm included NSAIDs, anti-epileptic drugs and opioids.

Patients who initiated medical cannabis for chronic pain were more likely to have polypharmacy with other pain medication but had similar comorbidity compared with those not on medical cannabis, according to the study.

The researchers reported that medical cannabis use was associated with a 180-day absolute risk for new-onset arrhythmia of 0.8% (95% CI, 0.6-1.1), whereas nonuse was linked to a 180-day absolute risk for new-onset arrhythmia of 0.4% (95% CI, 0.3-0.5), translating to a 180-day risk ratio of 2.07 (95% CI, 1.34-2.8) and a 1-year risk ratio of 1.36 (95% CI, 1-1.73).

Arrhythmia risk was similar when patients were stratified by CBD, combination CBD/THC and THC use.

“Both CBD and THC have an effect on the CB1R receptor, which theoretically could lead to CV side effects,” Holt told Healio. “Previously, side effects have been mostly suspected to be related to THC since the psychoactive properties of cannabis arise from this cannabinoid. Findings from this study suggest that both THC and CBD may play a role in the risk of CV side effects. Importantly, these findings could also be explained by unmeasured differences between the patients initiated on THC, CBD and CBD/THC products, respectively, meaning that some of the risk increase in one or more of the groups could be unrelated to cannabis use, ie, unmeasured confounding.”

Holt and colleagues also observed no significant association between medical cannabis use for chronic pain and risk for ACS (180-day risk ratio = 1.2; 95% CI, 0.35-2.04).

“This study adds important and much-needed data on CV side effects related to medical cannabis; however, clinicians should consider the observational nature of these findings which limits their impact and applicability for clinical recommendations before changing any practice,” Holt told Healio. “Considering all available data on medical cannabis treatment for chronic pain, I believe that it should probably be reserved for chronic pain conditions where the effect is supported by sufficient evidence, eg, neuropathic chronic pain. Considering data from this study, some improved monitoring of CV symptoms immediately following initiation could be beneficial, especially in patients with known cardiometabolic disease or history of cancer.”

‘Cannabis for therapeutic use’

Robert L. Page II

In a related editorial, Robert L. Page II, PharmD, MSPH, BCPS (AQ-cards), BCGP, FAHA, FHFSA, FCCP, FASHP, professor at the Skaggs School of Pharmacy and Pharmaceutical Sciences at the University of Colorado Anschutz Medical Campus, discussed the clinical implications of the findings and posited new terminology with which “medical” cannabis may be referenced.

“What clinical insights can be gained from these findings? … While THC rather than CBD has been the proposed culprit for the majority of CV side effects, the investigators found similar results regardless of the specific cannabinoid used, thus highlighting that both THC and CBD could be the culprits,” wrote Page, who chaired the writing group of an American Heart Association scientific statement on cannabis use and CVD. “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.

“When playwright William Shakespeare asked the question, ‘what’s in a name?’, he was referring to the idea that names themselves are a convention to distinguish things or people, but themselves may not have meaning,” he wrote. “I would argue that ‘cannabis for therapeutic use’ would be a more appropriate terminology rather than ‘medical.’ Nonetheless, cannabis by any name, whether recreational or medical, still ‘smells’ the same, and the odor is definitely not ‘sweet’ in terms of potential CV hazards.”


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