Diclofenac is an NSAID used to treat the signs and symptoms of osteoarthritis and rheumatoid arthritis. Diclofenac possesses anti-inflammatory, analgesic, and antipyretic activity. It targets the prostaglandin G/H synthase-1 (COX-1) and prostaglandin G/H synthase-2 (COX-2) in the cyclooxygenase pathway. The cyclooxygenase pathway begins in the cytosol with phospholipids being converted into arachidonic acid by the action of phospholipase A2. The rest of the pathway occurs on the endoplasmic reticulum membrane, where prostaglandin G/H synthase 1 & 2 convert arachidonic acid into prostaglandin H2. Prostaglandin H2 can either be converted into thromboxane A2 via thromboxane A synthase, prostacyclin/prostaglandin I2 via prostacyclin synthase, or prostaglandin E2 via prostaglandin E synthase. COX-2 is an inducible enzyme that is responsible for prostaglandin synthesis during inflammation. It leads to the formation of prostaglandin E2 which is responsible for contributing to the inflammatory response by activating immune cells and for increasing pain sensation by acting on pain fibers. Diclofenac inhibits the action of COX-1 and COX-2 on the endoplasmic reticulum membrane. This reduces the formation of prostaglandin H2 and therefore, prostaglandin E2 (PGE2). The low concentration of prostaglandin E2 attenuates the effect it has on stimulating immune cells and pain fibers, consequently reducing inflammation and pain. Inflammatory and infectious diseases trigger fever. Cytokines are produced in the central nervous system (CNS) during an inflammatory response. These cytokines induce COX-2 production that increases the synthesis of prostaglandin, specifically prostaglandin E2 which adjusts hypothalamic temperature control by increasing heat production. Because diclofenac decreases PGE2 in the CNS, it has an antipyretic effect. Antipyretic effects increase peripheral blood flow, vasodilation, and subsequent heat dissipation. It is administered in many different ways: as a topical ointment/cream/gel/patch, as an oral tablet/capsule, as an ophthalmic solution, and as a rectal suppository.

Diclofenac NSAID Pathway References