Postal address:
Norwegian Institute of Public Health
WHO Collaborating Centre for Drug Statistics Methodology
Postboks 222 Sk°yen
0213 Oslo

Visiting/delivery address:
Myrens verksted 6H
0473 Oslo

Tel:  +47 21 07 81 60

Guidelines for ATC classification and DDD assignment

The guidelines describe the ATC classification system and the DDD methodology. The publication consists of a general part with information about the system and procedures and data requirements for ATC/DDD assignment and alterations. The second part of the publication, the interpretative guidelines, describes the different ATC levels down to the 4th level. The comments included vary from one ATC group to another. No comments are given if the establishment of ATC codes and DDDs are considered to cause no special problems.

The interpretative guidelines should be consulted whenever the ATC/DDD system is used for drug utilization research. They describe particular issues, which have been discussed and resolved by consensus of the working group.

The guidelines are updated annually. The Guidelines can be ordered as a paper copy (English or Spanish versions) from the Centre (order form). A searchable version of the ATC/DDD Index linked to the text from the Guidelines is available on this website (ATC/DDD Index).

Suggested citation: WHO Collaborating Centre for Drug Statistics Methodology,  Guidelines for ATC classification and DDD assignment, 2024. Oslo, 2024.

A pdf version of the Guidelines is be available here:

 Guidelines 2014

Guidelines 2024 

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Last updated: 2024-03-01