No Benefit of Enteric-Coated Aspirin vs Uncoated in CVD


Enteric-coated aspirin is not significantly less effective than uncoated aspirin is in preventing death, myocardial infarction (MI), or stroke among patients with cardiovascular disease but is also not significantly safer in terms of bleeding risk, results of a post hoc analysis of data from a randomized clinical trial suggest.


  • This was a post hoc analysis of the 2021 open-label randomized ADAPTABLE (Aspirin Dosing: A Patient-Centric Trial Assessing Benefits and Long-term Effectiveness) trial that showed no statistical difference between high-dose (325 mg) and low-dose (81 mg) daily aspirin in death or hospitalization for MI or stroke among 15,076 patients with atherosclerotic cardiovascular disease and no significant difference in major bleeding between doses.

  • For the current analysis, researchers divided participants into subgroups based on randomized aspirin dose and self-reported aspirin formulation (enteric-coated or uncoated) and evaluated the safety and effectiveness of coated and uncoated aspirin in the two doses across 26.2 months.

  • Of participants enrolled in ADAPTABLE, 10,678 (70.1%) reported the aspirin formulation used; the median age of this sample was 68.0 years, 68.2% were men, and 84.0% were White.


  • In the enteric-coated aspirin group, the cumulative incidence of death, MI or stroke was 6.6% with the 81-mg dose and 7.1% with the 325-mg dose (adjusted hazard ratio [aHR], 1.13; 95% CI, 0.88-1.45), and there were similar results for uncoated aspirin (8.5% vs 7.6%; aHR, 0.99; 95% CI, 0.83-1.18) with an interaction of P = .41 across groups.

  • All-cause mortality also did not differ significantly (aHR, 0.88; 95% CI, 0.63-1.23 for enteric-coated aspirin vs aHR, 0.90; 95% CI, 0.72-1.13 for uncoated aspirin; interaction P = .90).

  • There was a small but significant increase in major bleeding in the higher-dose enteric-coated aspirin group (aHR, 2.37; 95% CI, 1.02-5.50), no difference in major bleeding in the uncoated aspirin cohort (aHR, 0.89; 95% CI, 0.49-1.64; interaction P = .07), and no significant difference in gastrointestinal tract bleeding.

  • The authors noted that the point estimate for major bleeding with enteric-coated aspirin showed an 18% relative risk reduction, although the 95% CI was wide, so a reduction in bleeding with coated aspirin can’t be reliably excluded.


“The results of this analysis did not show any difference in the effectiveness or safety outcomes analyzed by formulation of aspirin consumed regardless of the dose of aspirin participants were randomly assigned,” the authors conclude. They note that enteric-coated aspirin’s value has recently been called into question due to reduced aspirin bioavailability and the possibility of limited cardiovascular protection.


The study was carried out by Amber Sleem, DO, Department of Medicine, Ochsner Medical Center, New Orleans, and colleagues. It was published online on October 4, 2023 in JAMA Cardiology.


Only 70.1% of participants reported aspirin formulation at baseline, which they could have switched during the study, and unknown confounders may have affected choice of aspirin formulation. Use of enteric-coated aspirin was not part of the randomization stratification, so the data must be treated as if from an observational study. Enrollment of women and minority groups was relatively low, so generalizability of the results remains questionable.


The study received support from the Patient-Centered Outcomes Research Institute. Sleem has no relevant conflicts of interest; see paper for disclosures of other authors.

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