Fluoxetine. Molecular model of the antidepressant drug fluoxetine (C17.H18.F3.N.O), commonly known as Prozac. This is a member of the selective serotonin reuptake inhibitor (SSRI) class of drugs. It is used to treat major depressive disorder, as well as other mental disorders. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue), oxygen (red) and fluorine (cyan).