Medical ATC: Anatomical Therapeutic Chemical code. ATC is a unique code assigned to a medicine according to the organ or system it works on and how it works. The classification system is maintained by the World Health Organization (WHO). BNF: British National Formulary. The BNF is a reference book containing the standard list of medicines used in UK prescribing. BNF/Snomed: The BNF/Snomed mapping file published by the NHS Business Services Authority (NHSBSA) represents the mappign of BNF codes to Dictionary of Medicines and Devices (dm+d) Snomed codes CPRD: Clinical Research Practice Datalink (database used by most consortia in AIM) CPRD GOLD: Data contributed using the Vision software dm+d: dictionary of medicines and devices from the NHS