Aspirin or acetylsalicylic acid is a white crystalline powder which is used as a remedy for reducing inflammation and fever. Taken orally, it relieves mild or moderate pain so is therefore often used for headache and other moderately painful conditions. It is used, in much smaller doses than is used in pain relief, for its anticoagulant effect as in the prevention of coronary thrombosis (see HEART, DISEASES OF); aspirin should be used with caution in people with DYSPEPSIA or PEPTIC ULCER, and not at all in persons under 20 unless medically directed because of the risk of REYE'S SYNDROME. (See also ANALGESICS.)