Abstract: The present invention provides methods and compositions for preventing platelet aggregation and for treating individuals suffering from conditions or undergoing procedures that may result in unwanted platelet aggregation. In particular the invention provides to methods and compositions for arterial vessel pacification. The methods are based on the administration of a therapeutically effective amount of a glycoprotein IIb/IIIa receptor antagonist, e.g., xemilofiban. The treatment may commence prior to a medical or surgical procedure or an outbreak of a condition, either of which results in the activation of platelets that may lead to thrombus formation, and may continue thereafter.