Antiplatelet agents are used in patients with ischemic stroke not only in the acute stage, but also in the chronic stage, Aspirin at 160-300 mg/day is recommended within 24-48 h after onset, but is not a substitute for tissue plasminogen activator. Ozagrel sodium, a thromboxane A2 synthase inhibitor, is used in Japan within 5 days after onset of cerebral thrombosis, which also increases cerebral blood flow in the penumbral area. No other antiplatelet agents have been verified to be effective in the acute phase of cerebral ischemia. In the chronic phase of non-cardioembolic stroke, aspirin, clopidogrel or aspirin with extended-release dipyridamole represent the initial options used around the world. However, cilostazol, a phosphodiesterase inhibitor, has been approved for secondary prevention of ischemic stroke in Japan. Cilostazol is known to not prolong bleeding time. Combination therapies such as aspirin plus clopidpgrel, aspirin plus dipyridamole or aspirin plus cilostazol are used for high-risk patients, where risk is determined by factors such as diabetes mellitus, dyslipidemia, and major vessel occlusion or stenosis as diagnosed on magnetic resonance angiography or carotid echosonography. However, care is required regarding hemorrhagic complications. New antiplatelet agents such as P2Y12 ADP receptor antagonists (prasugrel, cangrelor, AZD 6140), thromboxane receptor antagonists (S18886-terutroban) and thrombin receptor antagonists (SCH530348) are under investigation.
