Codeine opiate drug, molecular model. This drug, sold as codeine sulphate, codeine phosphate or codeine hydrochloride, is used in the treatment of coughs, diarrhoea and pain. The drug binds to opiate receptors in different tissues with varying effects. For example, the analgesic (pain- relieving) effect is caused by activating receptors that depress neural activity in the brain. Codeine is found in low concentrations in opium, but is usually produced synthetically from morphine. Its easy availability makes it a popular recreational drug. In this model, atoms are represented by coloured spheres; carbon is yellow, hydrogen is white, oxygen is pink, and nitrogen is green.