Dabigatran reduces thrombin-induced platelet aggregation and activation in a dose-dependent manner

Dabigatran is an oral anticoagulant and a reversible inhibitor of thrombin. Further, dabigatran might affect platelet function through a direct effect on platelet thrombin receptors. The aim was to investigate the effect of dabigatran on platelet activation and platelet aggregation. Healthy donor blood was incubated with dabigatran 0, 50, 500 ng/mL, corresponding to the therapeutic range of dabigatran peak plasma concentrations, and 10,000 ng/mL comprising a supra-therapeutic dabigatran plasma level. Platelet aggregation was tested with 96-well aggregometry. Flow cytometry was used to test platelet activation and platelet thrombin receptor expression (SPAN-12 and WEDE-15 expression). Agonists were thrombin, thrombin receptor-activating peptide, protease-activated receptor-4 agonist, collagen, collagen-related peptide, arachidonic acid, and adenosine diphosphate. All concentrations of dabigatran fully inhibited platelet aggregation for thrombin up to 2 IU/mL, while dabigatran did not affect platelet aggregation by other agonists. Platelet activation (percentage of platelets positive for activated GPIIb/IIIa, CD63, P-selectin) was reduced after thrombin stimulation in samples with dabigatran levels ≥500 ng/mL. After stimulation with thrombin, the percentage of activated GPIIb/IIIa-positive platelets was 99.8 ± 0.2% without dabigatran, 14.7 ± 4.7% with 500 ng/mL dabigatran, and 4.2 ± 0.2% with 10,000 ng/mL dabigatran, both p < 0.001 when compared to samples without dabigatran. Also, the receptor expression of GPIIb/IIIa, CD63, and P-selectin were reduced after dabigatran treatment. The expression of thrombin receptors was reduced at dabigatran on ≥ 500 ng/mL. In conclusion, dabigatran exclusively inhibits thrombin-induced platelet activation and aggregation with a dose-dependent response. Platelet stimulation with other agonists was not affected by dabigatran.