Lansoprazole. Molecular model of the drug lansoprazole (C16.H14.F3.N3.O2.S), a proton-pump inhibitor that prevents the stomach from producing gastric acid. It is used in cases of gastric ulcers or gastroesophageal reflux disease. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue), oxygen (red), sulphur (yellow) and fluorine (cyan).