Diclofenac capsules (Zipsor, Zorvolex) and tablets (Cataflam) are used to relieve mild to moderate pain. Diclofenac extended-release tablets (Voltaren XR), tablets (Cataflam), and delayed-release tablets (available generically) are used to relieve pain, tenderness, swelling, and stiffness caused by osteoarthritis (arthritis caused by a breakdown of the lining of the joints), and rheumatoid arthritis (arthritis caused by swelling of the lining of the joints). Diclofenac extended-release tablets and delayed-release tablets are also used to treat ankylosing spondylitis (arthritis that mainly affects the spine). Diclofenac tablets (Cataflam) are also used to treat painful menstrual periods. Diclofenac solution (Cambia) is used to treat migraine headaches in adults, but cannot be used to prevent migraines or to treat other types of headaches. Diclofenac is in a class of medications called NSAIDs. It works by stopping the body's production of a substance that causes pain, fever, and inflammation.