Effects of Switching From Prasugrel to Ticagrelor
What are the pharmacodynamic effects of switching to ticagrelor in patients treated with prasugrel?
The SWAP-3 (Pharmacodynamic Evaluation of Switching From Prasugrel to Ticagrelor) authors performed a prospective, randomized, open-label, three-arm, parallel-design study in 82 patients who were on maintenance dual antiplatelet therapy with aspirin (81 mg QD) and prasugrel (10 mg QD). Patients were randomized to continue prasugrel 10 mg QD or switch to ticagrelor 90 mg bid, with or without a 180 mg loading dose (LD), for 1 week. Platelet function was assessed at 6 time points (baseline, 2 hours, 4 hours, 24 hours, 48 hours, and 1 week after randomization) using P2Y12 reaction units (PRU) by VerifyNow, platelet reactivity index by vasodilator-stimulated phosphoprotein (VASP), and platelet aggregation by light transmittance aggregometry (LTA).
There was a decline in PRU within 2 hours of switching to ticagrelor and the levels remained low during the study period. There was no increase in rates of high on-treatment platelet reactivity (PRU >208), which were overall very low throughout the study time course. Similar levels of platelet reactivity were observed with and without the use of a loading dose of ticagrelor. Similar findings were noted with the use of VASP and LTA.
The authors concluded that switching from prasugrel to ticagrelor leads to transiently higher levels of platelet inhibition, regardless of the use of a LD, without evidence of drug interactions.
Switching of P2Y12 inhibitors is common in clinical practice (Bagai A, et al., Circ Cardiovasc Interv 2014;7:585-93), and there are limited data on its clinical impact. This study demonstrated further platelet inhibition when a patient is switched from prasugrel to ticagrelor, although the clinical implication of this remains to be established.
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