Vioxx painkiller drug. Box and blister packs of Vioxx painkiller (analgesic) capsules. Each capsule contains 12.5 milligrams of the non- steroidal anti-inflammatory drug (NSAID) rofecoxib. 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. Vioxx was used mainly to relieve pain due to osteoarthritis, but was withdrawn due to fears that it increased the risk of heart attack.