ATC codes


  • ATC
  • ATC code

In the ATC classification system, the active substances are classified in a hierarchy with five different levels. The system has fourteen main anatomical/pharmacological groups or 1st levels. Each ATC main group is divided into 2nd levels which could be either pharmacological or therapeutic groups. The 3rd and 4th levels are chemical, pharmacological or therapeutic subgroups and the 5th level is the chemical substance. The 2nd, 3rd and 4th levels are often used to identify pharmacological subgroups when that is considered more appropriate than therapeutic or chemical subgroups 1.

A drug is given a specific code based on its inclusion in various abovementioned groups or subgroups, and this is referred to as an ATC code. As an example, the complete classification of Metformin illustrates the structure of the code for this drug 2.

In DrugBank, a list of ATC codes is visible under the "ATC codes" section of a drug entry 3. It is also possible to browse the ATC tree on DrugBank via the ATC Classification Browser.

In data exports and the DrugBank API, ATC codes are automatically and manually linked into DrugBank drugs, categories, and therapeutic categories. This allows a cross-mapping to other classification resources such as MeSH and RxNorm.


  1. World Health Organization ATC Codes [Link]
  2. Metformin ATC classification example [File]
  3. Metformin ATC codes example, DrugBank [File]