Hydrocodone drug. Molecular model of the analgesic drug hydrocodone (C18H21NO3). Atoms (spheres) are colour-coded: carbon (yellow), hydrogen (white), nitrogen (blue, just visible at lower right) and oxygen (red, upper left). Hydrocodone is an opiate analgesic (painkiller). It is usually taken in a formulation where it has been combined with other drugs, such as paracetamol or aspirin.