Ketoprofen (RP-19583) is a propionic acid derivate and nonsteroidal anti-inflammatory drug (NSAID) with anti-inflammatory, analgesic and antipyretic effects. Ketoprofen inhibits the activity of the enzymes cyclo-oxygenase I and II, resulting in a decreased formation of precursors of prostaglandins and thromboxanes. The resulting decrease in prostaglandin synthesis, by prostaglandin synthase, is responsible for the therapeutic effects of ibuprofen. Ketoprofen also causes a decrease in the formation of thromboxane A2 synthesis, by thromboxane synthase, thereby inhibiting platelet aggregation.

S-(+)-Ketoprofen ((S)-(+)-Ketoprofen) works by blocking the action of a substance in the body called cyclo-oxygenase. It belongs to a class of medicines called non-steroidal anti-inflammatory drugs (NSAIDs). Cyclo-oxygenase is involved in the production of chemicals in the body called prostaglandins. Prostaglandins are produced in response to injury or certain diseases and would otherwise go on to cause swelling, inflammation and pain. By blocking cyclo-oxygenase, S-(+)-Ketoprofen prevents the production of prostaglandins and therefore reduces inflammation and pain. Along with Peripheral analgesic action it possesses central analgesic action.S-(+)-Ketoprofen is a non-steroidal anti-inflammatory drug. It is manufactured by Menarini, under the tradename Keral. It is available in the UK, as S-(+)-Ketoprofen trometamol, as a prescription-only drug and in Latin America as Miracox, produced by Stein in Costa Rica. In Italy it is available as an over the counter-drug under the tradename Enantyum. In Lithuania it is available as over the counter-drug uder tradename Dolmen.