<p>Diclofenac is a phenylacetic acid derivative and non-steroidal anti-inflammatory drug (NSAID).<sup class="text-reference-group"><a class="reference-popover-link" data-content="Official drug label" href="#label-reference">Label</a></sup> NSAIDs inhibit cyclooxygenase (COX)-1 and-2 which are the enzyme responsible for producing prostaglandins (PGs). PGs contribute to inflammation and pain signalling. Diclofenac, like other NSAIDs, is often used as first line therapy for acute and chronic pain and inflammation from a variety of causes. Diclofenac was the product of rational drug design based on the structures of <a href="https://go.drugbank.com/drugs/DB00812">phenylbutazone</a>, <a href="https://go.drugbank.com/drugs/DB00784">mefenamic acid</a>, and <a href="https://go.drugbank.com/drugs/DB00328">indomethacin</a>.<sup class="text-reference-group"><a class="reference-popover-link" data-content="Sallmann AR: The history of diclofenac. Am. J. Med. 1986 Apr 28;80(4):29-33." href="#reference-A180796">12</a></sup> The addition of two chlorine groups in the ortho position of the phenyl ring locks the ring in maximal torsion which appears to be related to increased potency. It is often used in combination with <a href="https://go.drugbank.com/drugs/DB00929">misoprostol</a> to prevent NSAID-induced gastric ulcers. Diclofenac was first approved by the FDA in July 1988 under the trade name Voltaren, marketed by Novartis (previously Ciba-Geigy).<sup class="text-reference-group"><a class="reference-popover-link" data-content="Drugs@FDA: Voltaren Delayed Release" href="#reference-L7360">18</a></sup></p>