Painkillers. Box and blister packs of Indocid painkilling (analgesic) drugs. The pills each contain 25 milligrams of the non-steroidal anti- inflammatory drug (NSAID) indomethacin. NSAIDs work by preventing the production of prostaglandins, chemicals in the body which cause inflammation and aid the transmission of pain signals to the brain. Side-effects of indomethacin include dizziness and headaches.