A gel formulation of the sodium salt of diclofenac, a nonsteroidal benzeneacetic acid derivative with analgesic, antipyretic and anti-inflammatory activities. Diclofenac binds to and chelates both isoforms of cyclooxygenase (COX-1 and-2), thereby blocking the conversion of arachidonic acid (AA) to pro-inflammatory prostaglandins. This agent may also inhibit lipoxygenases, resulting in the inhibition of pro-inflammatory leukotriene synthesis from AA. or The gel form of a drug that is used to treat the symptoms of rheumatoid arthritis and is being studied in the prevention and treatment of some types of skin cancer. It blocks substances that cause inflammation and pain. It may also prevent the growth of new blood vessels that tumors need to grow. It is a type of cyclooxygenase inhibitor, a type of nonsteroidal anti-inflammatory drug (NSAID), and a type of antiangiogenesis agent. Also called Voltaren gel.