Heroin. Computer model of a molecule of heroin (diamorphine, C21.H23.N.O5). The atoms (spheres) of this drug are colour-coded: carbon (green), hydrogen (yellow), oxygen (blue) and nitrogen (pink). This drug is a powerful narcotic (inducing a stupor) and analgesic (relieving pain) that is derived from morphine. It is easily absorbed by the brain due to its lipid-like (fat-like) nature. Its use in medicine is restricted, as regular use can lead to addiction. It is abused by drug users and is illegal in many countries. Regular users need high doses to achieve a 'high' as they become tolerant to the effects of the drug. Death by an overdose is a common result.