Current patterns of P2Y12 receptor inhibitor use provide an excellent opportunity to test the impact of copayment reduction on clinician choice of medication, patient adherence, and clinical outcomes. The ARTEMIS trial is a practical multicenter, cluster- randomized clinical trial that will assess the impact of copayment reduction by equalizing the copayment of clopidogrel and ticagrelor. ARTEMIS will assess prescribing patterns, patient medication adherence, and clinical outcomes up to one year. We hypothesize that reducing out--of--pocket cost for P2Y12 receptor inhibitor will lead to improved adherence. Additionally, copayment reduction of both generic and brand antiplatelet agents may lead to a reduction in MACE risk. This is in part due to greater adherence to an evidence--based secondary prevention medication. Additionally the reduction in MACE may reflect greater selection of a more potent antiplatelet agent that has been shown to reduce MACE in randomized clinical trials, as provider choice of antiplatelet therapy will be primarily driven by risk- benefit assessment rather than the cost burden to the patient.