The ATC/DDD Index is used to classify medicines by anatomical, therapeutic and chemical characteristics and to support standardised drug-utilisation work. It is distinct from MedDRA, which codes medical concepts and adverse-event information, and WHODrug, which identifies medicinal products and drug names.
WHO ATC/DDD Index
Official searchable ATC classification and Defined Daily Dose index maintained by the WHO Collaborating Centre for Drug Statistics Methodology.