Aspirin, ibuprofen, acetaminophen and naproxen are pain medications that do not require a prescription, according to WebMD. These drugs alleviate pain and reduce fevers. Aspirin, ibuprofen and naproxen also relieve inflammation, and are known as nonsteroidal anti-inflammatory drugs, or NSAIDs.
Nonsteroidal anti-inflammatory drugs work by blocking prostaglandins. Since NSAIDs block the prostaglandins that cause pain, they also block the ones that protect the stomach lining, sometimes causing upset stomach or gastrointestinal bleeding in some people, explains Elizabeth Quinn for About.com Acetaminophen drugs such as Tylenol and Panadol are believed to act on the pain centers in the brain, and are the safest pain relievers because they do not cause any gastrointestinal bleeding. Acetaminophen is sometimes used to treat osteoarthritis and high blood pressure. Too high of a dose of acetaminophen may cause liver damage.