RESUMEN
BACKGROUND: Aspirin resistance has been defined as inability of aspirin to protect individuals from thrombotic complications or to produce an anticipated effect from laboratory tests of platelet function. Most reported information comes from Western patients with coronary artery disease and aspirin resistance is defined by laboratory criteria. The purpose of the present study was to look for aspirin non-responders in Thai patients who presented with acute/subacute ischemic stroke and transient ischemic attack (TIA). MATERIAL AND METHOD: The authors prospectively included acute ischemic stroke/TIA patients who were treated at Thammasat Hospital from August, 2006 to July, 2007 and had already been on aspirin. Information about compliance of medication, reasons for taking aspirin, doses of aspirin, baseline characteristics, and stroke subtypes of the patients were collected. RESULTS: There were 194 acute/subacute ischemic stroke/TIA patients during the study period Forty-six patients (23.7%), who had already been on aspirin (aspirin non-responder), while having new stroke/TIA, were studied Eighteen patients were on aspirin 300-325 mg and 28 patients were on 81 mg per day. Most patients had taken aspirin 300-325mg/day as secondary prevention, while half of the patients taking aspirin 81 mg/d had diabetes mellitus and took aspirin as primary prevention. CONCLUSION: Aspirin non-responders in ischemic stroke patients are common. Future study is required to clarify mechanisms of aspirin non-responders in Thai patients.