There are many medicines that help prevent blood clots from forming, reducing the risk of full-blown stroke:
Aspirin - the least expensive and most common of these medicines
Aggrenox®- a combination of aspirin and extended-release dipyridamole
Warfarin (CoumadinTM)- commonly prescribed to prevent clots from forming in patients with atrial fibrillation
Statins used for treatment of high cholesterol and blood pressure control may also reduce stroke risk.