The ATC classification
Structure
In the Anatomical Therapeutic Chemical (ATC) classification system, drugs are divided into different groups according to the organ or system on which they act and their chemical, pharmacological and therapeutic properties.
Drugs are classified in groups at five different levels. The drugs are divided into fourteen main groups (1st level), with one pharmacological/therapeutic subgroup (2nd level). The 3rd and 4th levels are chemical/pharmacological/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.
The complete classification of metformin illustrates the structure of the code:
|
A |
Alimentary tract and metabolism
(1st level, anatomical main group) |
|
A10 |
Drugs used in diabetes
(2nd level, therapeutic subgroup) |
|
A10B |
Oral blood glucose lowering drugs
(3rd level, pharmacological subgroup) |
|
A10B A |
Biguanides
(4th level, chemical subgroup) |
|
A10B A02 |
Metformin
(5th level, chemical substance) |
Thus, in the ATC system all plain metformin preparations are given the ATC code A10B A02.
Nomenclature
- International non-proprietary names (INN) are preferred. If INN names are not assigned, USAN (United States Adopted Name) or BAN (British Approved Name) names are usually chosen.
- WHO’s list of drug terms is used when naming the different ATC levels.
Inclusion and exclusion criteria
The WHO Collaborating Centre for Drug Statistics Methodology in Oslo establishes new entries in the ATC classification on request from the users of the system. These include manufacturers, regulatory agencies and researchers. The coverage of the system is not comprehensive. A major reason why a substance is not included is that no request has been received.
The Centre gives priority to plain preparations containing well-defined substances which have an INN name and which are:
- New Chemical Entities and biologicals proposed for licensing in a range of countries
- Existing well-defined substances used in a variety of countries
- Other medicines are considered on a case by case basis
Official ATC codes for combined preparations are assigned only to a limited extent. Combinations likely to be widely used internationally, however, are given an ATC code (e.g. beta blockers and diuretics).
A new medicinal substance is normally not included in the ATC system before an application for marketing authorisation is submitted in at least one country. In general complementary and traditional medicinal products are not included in the ATC system.