The Anatomical Therapeutic Chemical (ATC) Classification System
In the ATC system the drug substances are classified into groups at 5 different levels. The drugs are divided into fourteen main groups (1st level), then further divided into pharmacological/ therapeutic subgroups (2nd level). The 3rd and 4th levels are chemical, pharmacological or therapeutic subgroups and the 5th level is the chemical substance/active ingredient.
The ATC code
A complete classification of spironolactone with the ATC code C03DA01 illustrates the structure of the ATC system:
| C |
Cardiovascular system
(1st level, anatomical main group) |
| 03 |
Diuretics
(2nd level, therapeutic subgroup) |
| D |
Potassium-sparing agents
(3rd level, pharmacological subgroup) |
| A |
Aldosterone antagonists
(4th level, pharmacological subgroup) |
| 01 |
Spironolactone
(5th level, chemical substance) |
All products containing spironolactone (Aldactone
® and Spirix
®) are assigned the code C03DA01.
The ATC classification system makes it possible to compile drug statistics on 5 different levels, that is, figures showing total consumption of all products classified in main group C -
Cardiovascular system (1st level), figures for the various subgroups (2nd, 3rd and 4th levels), and down to figures showing consumption of each active ingredient.
The ATC code for all pharmaceuticals on the Norwegian market can be found in the
pharmacy medicinal product register and in the monographs of the national drug catalogue
Felleskatalogen.
The WHO Collaborating Centre for Drug Statistics Methodology
In 1982 the WHO Regional Office for Europe established a coordinating centre at NMD in Oslo; the
WHO Collaborating Centre for Drug Statistics Methodology. In May 1996 the Centre was attached to the WHO Headquarter in Geneva due to the increasing global use of the ATC/DDD system. The main tasks of the WHO Centre are to classify drugs according to the ATC system, assign Defined Daily Doses and to further develop the ATC/DDD system. This work is performed in close cooperation with a global expert group representing 12 different countries. As from 2002 the Centre has been located at the Norwegian Institute of Public Health.