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

Visiting/delivery address:
Marcus Thranes gate 6
0473 Oslo

Tel:  +47 21 07 81 60

Application for ATC alterations

Principles for ATC alterations
As the selection of drugs and their uses are continually changing and expanding, regular revisions of the ATC system will always be necessary.

Changes in the ATC classification should be kept to a minimum.  An important aim is to keep a stable classification system over time with as few changes as possible and still have a classification where new therapy and new pharmacological principles find an appropriate place.  Before alterations are made, any potential difficulties for the use of the ATC system in drug utilization monitoring and research are considered and related to the benefits that could be achieved by the alteration.

Alterations in ATC classification can be made when the main use of a drug has clearly changed, and when new groups are required to accommodate new substances or to achieve better specificity in the groupings.  Other reasons for changes can be new knowledge about mechanism of action or the need for splitting large and complex groups.

When it is decided to make an alteration, the following principles are used:

  • When new therapeutic or pharmacological ATC groups are assigned, it should always be considered if there are substances in other groups that should be included in the new group.
  • When changing ATC codes for plain products, it should always be considered if it is necessary to change the ATC code for any combination products with the same active ingredient.
  • When an ATC code is changed for a substance, the previous code is not reused for new substances.

When an ATC code is altered, the DDD is also reviewed.

Data requirement (to the top)
When requesting changes to ATC classifications, the data requirements are similar to the data required for new ATC codes.  An important basis for the ATC/DDD system is to maintain a stable system for drug consumption studies.  For this reason, there need to be compelling reasons for changing ATC codes.  It is therefore important to submit data, which justify the proposed change.

If a change in the main therapeutic use is the reason for the proposed change, the data submitted should clearly indicate this change (e.g. market research data showing the percentage use for the different indications in a range of countries).

If new knowledge of pharmacology or mechanism of action is the reason for the proposed change, relevant evidence should be submitted.

If the proposed change is to establish specific ATC groups for one or more substances already classified in another group (usually a various group), it is necessary to submit data that verify that the change is beneficial and represents an improvement of the ATC classification for presenting drug consumption statistics.  Justifications based on use of the system in reimbursement, for pricing or marketing reasons will not be considered.

Procedures (to the top)
Any user may in principle propose changes to ATC classifications.  There is no application form for ATC alterations. Proposal for changes should be sent to the WHO Collaborating Centre for Drug Statistics Methodology, and all proposals will be discussed in the WHO International Working Group for Drug Statistics Methodology.

The steps in the evaluation procedure for changes to ATC classifications are as follows:

  • The Centre will confirm receipt of the proposal for a change and give information about the time schedule for discussion at the Working Group meeting.
  • After approval of the minutes of the Working Group meeting, the decision from the meeting concerning the proposed change is distributed from the Centre to those requesting the change (the applicant).  Independent of whether it has been decided to change or not, a deadline will be allowed for the applicant to comment or object to this decision.
  • If it is decided to make a change, notification of this change is published on the website (New ATC codes and alterations) and in the next issue of the publication WHO Drug Information.
  • If objections, justified on submitted evidence, are received, the ATC alteration will be discussed again at the following meeting of the Working Group, and a final decision will then be taken.
  • If no objections are received, the altered ATC classification will be implemented in the next issue of the ATC classification index.

Deadlines for applications (to the top)
Deadlines for applications

Last updated: 2018-02-13