Analgesics are medicines used to relieve pain such as headaches, backaches, joint pain, sore muscles, menstrual cramps, and pain that results from surgery, injury, or illness. While these drugs do not treat whatever is causing the pain, they can provide enough relief to make people more comfortable and to allow them to carry out their daily routines.

Pain is the body's signal that something is wrong. Pain can result from an injury, such as a broken bone, a burn or a sprain; from overuse of muscles (including muscle tension due to stress); from infections, such as sinus infections or meningitis; or from natural events, such as childbirth.

Pain begins at the level of the cells. In response to injury or inflammation, cells release chemical messengers. These chemical messengers alert other specialized cells called pain receptors. The pain receptors send signals to the brain. The brain interprets the signals...