Antiplatelet drugs (e.g. aspirin) are active substances that act in different ways to prevent blood clotting. They are used to prevent blood clots (thromboses) that occur e.g. in strokes or heart attacks, or as after care following heart operations. Antiplatelet drugs can have various side effects, such as gastrointestinal bleeding, and kidney damage. The Swiss Atlas of Healthcare shows antiplatelet drugs dispensed by outpatient care providers.