section_path: Prevention/Risk factors/Anticoagulant drugs
section_name: Anticoagulant drugs
paragraph_text: Anticoagulant drugs
  
  Oral anticoagulants such as warfarin have been the mainstay of stroke prevention for over 50 years. However, several studies have shown that aspirin and other antiplatelets are highly effective in secondary prevention after stroke or transient ischemic attack. Low doses of aspirin (for example 75–150 mg) are as effective as high doses but have fewer side effects; the lowest effective dose remains unknown. Thienopyridines (clopidogrel, ticlopidine) might be slightly more effective than aspirin and have a decreased risk of gastrointestinal bleeding but are more expensive. Both aspirin and clopidogrel may be useful in the first few weeks after a minor stroke or high-risk TIA. Clopidogrel has less side effects than ticlopidine. Dipyridamole can be added to aspirin therapy to provide a small additional benefit, even though headache is a common side effect. Low-dose aspirin is also effective for stroke prevention after having a myocardial infarction.
  
  Those with atrial fibrillation have a 5% a year risk of stroke, and those with valvular atrial fibrillation have an even higher risk. Depending on the stroke risk, anticoagulation with medications such as warfarin or aspirin is useful for prevention with various levels of comparative effectiveness depending on the type of treatment used.
  
  Oral anticoagulants, especially Xa (apixaban) and thrombin (dabigatran) inhibitors, have been shown to be superior to warfarin in stroke reduction and have a lower or similar bleeding risk in patients with atrial fibrillation. Except in people with atrial fibrillation, oral anticoagulants are not advised for stroke prevention—any benefit is offset by bleeding risk.
  
  In primary prevention, however, antiplatelet drugs did not reduce the risk of ischemic stroke but increased the risk of major bleeding. Further studies are needed to investigate a possible protective effect of aspirin against ischemic stroke in women.