Diclofenac, sold under the brand name Voltaren, among others, is a nonsteroidal anti-inflammatory drug (NSAID) used to treat pain and inflammatory diseases such as gout. It is taken by mouth or rectally in a suppository, used by injection, or applied to the skin. Improvements in pain last for as much as eight hours. It is also available in combination with misoprostol in an effort to decrease stomach problems.Common side effects include abdominal pain, gastrointestinal bleeding, nausea, dizziness, headache, and swelling. Serious side effects may include heart disease, stroke, kidney problems, and stomach ulceration. Use is not recommended in the third trimester of pregnancy. It is likely safe during breastfeeding. It is believed to work by decreasing the production of prostaglandin. It blocks both COX-1 (like aspirin) and COX-2 (like celecoxib), hence is a COX-2 inhibitor.Diclofenac was patented in 1965 by Ciba-Geigy; it came into medical use in the United States in 1988. It is available as a generic medication. In 2019, it was the 74th most commonly prescribed medication in the United States, with more than 10 million prescriptions. It is available as a sodium or potassium salt. It is also widely used for livestock; such use was responsible for the Indian vulture crisis, during which in a few years 95% of the countrys vulture population was killed, and in many countries agricultural use is now forbidden. Medical uses
Diclofenac is used to treat pain, inflammatory disorders, and dysmenorrhea.
These additional actions may explain its high potency – it is the most potent NSAID on a broad basis.Marked differences exist among NSAIDs in their selective inhibition of the two subtypes of cyclooxygenase, COX-1 and COX-2. Much pharmaceutical drug design has attempted to focus on selective COX-2 inhibition as a way to minimize the gastrointestinal side effects of NSAIDs such as aspirin. In practice, use of some COX-2 inhibitors with their adverse effects has led to massive numbers of patient family lawsuits alleging wrongful death by heart attack, yet other significantly COX-selective NSAIDs, such as diclofenac, have been well tolerated by most of the population.Besides the COX-inhibition, a number of other molecular targets of diclofenac possibly contributing to its pain-relieving actions have recently been identified. These include:

Blockage of voltage-dependent sodium channels (after activation of the channel, diclofenac inhibits its reactivation also known as phase inhibition)
Blockage of acid-sensing ion channels (ASICs)
Positive allosteric modulation of KCNQ- and BK-potassium channels (diclofenac opens these channels, leading to hyperpolarization of the cell membrane)The action of one single dose is much longer (6 to 8 h) than the very short 1.2–2 h half-life of the drug would indicate. This could be partly because it persists for over 11 hours in synovial fluids. As a veterinary drug
Diclofenac is widely approved as a veterinary drug. It is used in the treatment of companion animals and livestock. In sheep, pigs, cattle and goats, it is used in the management of several bacterial diseases, including diarrhoea, enteritis, dysentery, foot rot and septicaemia.