Resistance to antiplatelet drugs (aspirin, clopidogrel) is a recognized phenomenon with a prevalence from 17% to 35%. Resistance as detected by in vitro tests such as Multiple Electrode Aggregometry (MEA) has been shown to predict clinical therapy failure. Resistance can be caused by clinical, cellular and pharmacogenetic factors. Non compliance is suspected to be an important contributing factor. In this study, compliance will be assured with an electronical compliance monitoring system. Factors to non response will be identified to find plausible explanations when in vitro platelet aggregation inhibition is insufficient despite assured compliance. This study will help to disclose the relationship between compliance, biomarker and clinical outcome as well as to quantify the impact of non compliance to the resistance phenomenon as measured by MEA.

Inclusion Criteria:

• Patients prescribed aspirin and/or clopidogrel for both including both cardiovascular and cerebrovascular indications seeing their general practitioner in or nearby Olten/SO for any medical purpose
• Patients with oral and written German language ability

Exclusion Criteria:

• Patients living in care homes
• Patients not preparing their drugs on their own (e.g. outpatient medical assistance through "spitex").
• Patients with acute cardiac symptoms

Patients with a prescription for aspirin and/or clopidogrel seeing their general practitioner (GP) for any purpose