Pharmacodynamic Comparison of Two Aspirin Formulations in the Caribbean: The ARC Study

Introduction: This prospective, single-arm, crossover pharmacodynamic study assessed the effect of Bayer low-dose enteric-coated aspirin 81 mg tablets (LD EC-ASA) (Bayer AG, Leverkusen, North Rhine-Westphalia, Germany) compared to Vazalore low-dose phospholipid-aspirin liquid-filled 81 mg capsules (LD PL-ASA) (PLx Pharma Inc., Sparta, NJ, USA) on platelet reactivity with respect to aspirin reaction units (ARU).

Methods: Forty-seven healthy volunteers were recruited. Platelet function was evaluated with the VerifyNow™ ARU assay (Werfen, Bedford, MA, USA) and assessed post-initiation of Bayer LD EC-ASA daily for 14 days, with a washout period of 28 days, followed by Vazalore LD PL-ASA daily for 14 days, again followed by ARU testing.

Results: Participants on LD EC-ASA had a mean ARU score of 426, with 19.1% of participants having an ARU > 550; patients on LD PL-ASA derived a mean ARU score of 435, with 14.9% achieving an ARU > 550. There were no significant differences in aspirin resistance (ARU > 550) according to the formulation (Bayer LD EC-ASA vs. Vazalore LD PL-ASA) used. Aspirin resistance was independent of ethnicity regardless of the formulation used. In addition, there were no significant associations between body surface area (BSA) and Bayer LD EC-ASA ARU value (p value 0.788) or Vazalore LD PL-ASA ARU value (p value 0.477). No patients experienced any serious adverse events or treatment-emergent adverse events.

Conclusions: There were no significant differences in aspirin resistance between Bayer LD EC-ASA and Vazalore LD PL-ASA. This dedicated pharmacodynamic study could potentially be informative and applicable for Trinidadian patients on dual antiplatelet therapy (DAPT). Further studies are required to confirm these exploratory findings.

Trial Registration: ClinicalTrials.gov identifier, NCT06228820, prospectively registered 1/18/2024.