Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) taken to reduce inflammation, such as in arthritis or acute injury.

Diclofenac is used for musculoskeletal complaints, especially arthritis (rheumatoid arthritis, osteoarthritis, spondylarthritis,ankylosing spondylitis), and pain management in case of kidney stones and gallstones. An additional indication is the treatment of acute migraine attacks. Diclofenac is used commonly to treat mild to moderate postoperative or posttraumatic pain, particular when inflammation is also present. Its an effective drug against menstrual pain.

The exact mechanism of action is not entirely known, but it is thought that the primary action responsible for its anti-inflammatory/antipyretic/analgesic action is through inhibition of prostaglandin synthesis by inhibition of cyclooxygenase (COX). Diclofenac, it seems, may also be a unique member of the NSAIDs. There is some evidence that diclofenac inhibits the lipooxygenase pathways, thus reducing formation of the leukotrienes (also pro-inflammatory autacoids). There is also speculation that diclofenac may inhibit phospholipase A2 as part of its mechanism of action. These additional actions may explain the high potency of diclofenac - it is the most potent NSAID on a molar basis. Inhibition of COX also decreases prostaglandins in the epithelium of the stomach, making it more sensitive to corrosion by gastric acid. This is also the main side effect of diclofenac. Diclofenac has a low to moderate preference to block the COX2-isoenzyme (approx. 10-fold) and is said to have therefore a somewhat lower incidence of gastrointestinal complaints than noted with indomethacin and aspirin.

Formal Chemical Name (IUPAC)
2-[(2,6-dichlorophenyl)amino]benzeneacetic acid

References

http://en.wikipedia.org/wiki/Diclofenac