Aspirin is a common over-the-counter medication used to treat pain, inflammation, and fever. It is also known as acetylsalicylic acid and is one of the most widely used drugs in the world. ASPIRIN is often referred to as a 'pill for pain' because it is an effective treatment for many types of pain, including headaches, muscle aches, and arthritis. ASPIRIN works by blocking the production of certain hormones that cause inflammation and pain.