Heart drug. Computer artwork of six aspirin pills with a human heart in the background. Aspirin (acetylsalicylic acid) is known to prevent internal blood clotting. This can help to prevent heart attacks and strokes. The pills are scored with a groove so that they can be easily broken for half doses. It is thought that a daily dose of a half an aspirin can reduce the risk of heart attacks and strokes. Aspirin is a common analgesic (painkiller) used to treat mild pain and can reduce the effects of fever.