In healthy volunteer studies, aspirin at a dose of 75 mg once daily provided only a small additional effect on platelets to prasugrel ex vivo (Leadbeater et al 2011) and similar findings have been shown with prasugrel (Armstrong et al 2011) and ticagrelor (Kirkby et al 2011) in vitro, however the clinical significance of this additional effect is not known as studies have not been made in patients with acute coronary syndrome, in whom platelet activation occurs and persists after the acute period (Ault, Cannon et al. 1999).