The Anatomical Therapeutic Chemical (ATC) classification system is used for the classification of drugs. It is published by the World Health Organization (WHO).
The classification is based on therapeutic and chemical characteristics of the drugs. Each ATC code is divided into 5 levels:
               1st level: Anatomical main group
               2nd level: Therapeutic main group
               3rd level: Therapeutic/pharmacological subgroup
               4th level: Chemical/therapeutic/pharmacological subgroup
               5th level: Chemical substance
Substances or combination of substances in the 5th level refer to a single indication. Drugs having more than one indication belong to more than one ATC code. Moxifloxacin for example has 2 ATC codes (S01AE07, J01MA14) assigned .