Aspirin molecule. Computer artwork showing the structure of a molecule of aspirin (acetylsalicylic acid). Atoms are represented as spheres and are colour-coded: carbon (black), hydrogen (white), and oxygen (red), with the bonds between them as rods. Aspirin is a non-steroidal anti-inflammatory drug (NSAID). It is taken as an analgesic (painkiller), antipyretic (reduces fever) and anticoagulant (prevents blood clotting). It is converted to salicylic acid and acetic acid in the body. The binding of salicylic acid deactivates the cyclooxygenase enzyme and is how aspirin has its effect.