Antiplatelet drugs decrease platelet aggregation and inhibit thrombus formation in the arterial circulation, because in faster-flowing vessels, thrombi are composed maily of platelets with little fibrin.

Use of aspirin in primary prevention of cardiovascular events, in patients with or without diabetes, is of unproven benefit. Long-term use of aspirin is of benefit in established cardiovascular disease (secondary prevention); unduly high blood pressure must be controlled before aspirin is given. If the patient is at high risk of gastro-intestinal bleeding, a proton pump inhibitor can be added.

Prescribing for secondary prevention should be in line with GEH guidelines.