Ibuprofen. Computer molecular model of ibuprofen (molecular formula: C13.H18.O2), a non-steroidal anti-inflammatory drug (NSAID). It is composed of carbon (grey), hydrogen (white) and oxygen (red). Although the exact mechanism of action is not understood, it is thought that ibuprofen prevents the synthesis of prostaglandin by inhibition of the enzyme cyclo-oxygenase and this leads to the drug's anti-inflammatory, painkilling properties.