Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) of the phenylacetic acid class with anti-inflammatory, analgesic, and antipyretic properties. Contrary to the action of many traditional NSAIDs, diclofenac inhibits cyclooxygenase (COX)-2 enzyme with greater potency than it does COX-1. In addition diclofenac can inhibit the thromboxane-prostanoid receptor, affect arachidonic acid release and uptake, inhibit lipoxygenase enzymes, and activate the nitric oxide-cGMP antinociceptive pathway. Other novel mechanisms of action may include the inhibition of substrate P, inhibition of peroxisome proliferator activated receptor gamma (PPARgamma), blockage of acid-sensing ion channels, alteration of interleukin-6 production, and inhibition of N-methyl-D-aspartate (NMDA) receptor hyperalgesia. Similar to other NSAIDs, diclofenac is associated with serious dose-dependent gastrointestinal, cardiovascular, and renal adverse effects. Since its introduction in 1973, a number of different diclofenac-containing drug products have been developed with the goal of improving efficacy, tolerability, and patient convenience. Delayed- and extended-release forms of diclofenac sodium were initially developed with the goal of improving the safety profile of diclofenac and providing convenient, once-daily dosing for the treatment of patients with chronic pain. New drug products consisting of diclofenac potassium salt were associated with faster absorption and rapid onset of pain relief. These include diclofenac potassium immediate-release tablets, diclofenac potassium liquid-filled soft gel capsules, and diclofenac potassium powder for oral solution. The advent of topical formulations of diclofenac enabled local treatment of pain and inflammation while minimizing systemic absorption of diclofenac. SoluMatrix diclofenac, consisting of submicron particles of diclofenac free acid and a proprietary combination of excipients, was developed to provide analgesic efficacy at reduced doses associated with lower systemic absorption. The drug's likely impact on the Asian vulture population was widely reported. The dramatic mortality was attributed largely to renal failure caused by exposure to diclofenac in livestock carcasses on which the birds fed. Although not the most endearing species, vultures are important environmental scavengers and, since veterinary use of diclofenac was stopped in the region in 2006, the decline in vulture numbers has slowed.

4'-Hydroxy diclofenac, a metabolite of diclofenac, suppresses prostaglandin E2 production specifically by blocking cyclooxygenase-2 activity and demonstrates anti-inflammatory properties.

Aceclofenac is a non-steroidal anti-inflammatory drug (NSAID) analog of Diclofenac. It is used for the relief of pain and inflammation in rheumatoid arthritis, osteoarthritis and ankylosing spondylitis. The dose is 100 mg twice daily, and should not be given to people with porphyria or breastfeeding mothers and is not recommended for children. Aceclofenac is a cytokine inhibitor. Aceclofenac works by blocking the action of a substance in the body called cyclo-oxygenase. Cyclo-oxygenase is involved in the production of prostaglandins (chemicals in the body which cause pain, swelling and inflammation). Aceclofenac is the glycolic acid ester of diclofenac. The incidence of gastric ulcerogenicity of aceclofenac has been reported to be significantly lower than that of other frequently prescribed NSAIDs: for instance, 2-fold less than naproxen, 4-fold less than diclofenac, and 7-fold less than indomethacin. Aceclofenac is metabolized in human hepatocytes and human microsomes to form [2-(2',6'-dichloro-4'-hydroxy- phenylamino)phenyl] acetoxyacetic acid as the major metabolite, which is then further conjugated.