Postal address:
WHO Collaborating Centre for Drug Statistics Methodology
Norwegian Institute of Public Health
P.O.Box 4404 Nydalen
0403 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 drugs available 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.  Before alterations are made, difficulties arising for the users of the ATC system are considered and related to the benefits achieved by the alteration.

Alterations in ATC classification are 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.

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

  • Space is provided for possible future extension of an ATC group.
  • The ATC code assigned to combination products should correspond as far as possible with the classification of the single substances in question.
  • Obsolete drugs or drugs withdrawn from the market are kept in the ATC system, since exclusion of substances from the ATC system may create difficulties for the users of the system when considering historical data.
  • Changes of currently valid codes are kept to a minimum.  A gap in the sequence is preferred to changing codes.

When an ATC code is altered, the DDD is also reviewed.  For example, when the classification of chloroquine was changed from ATC group M to P (i.e. classified only as an antimalarial), the DDD was changed since the dosages used for treatment of malaria are different from the dosages used for rheumatic disorders.

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 database 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 reimbursement, pricing or marketing reasons will not be considered.

(to the top)
A change in the ATC classification should be proposed and explained in writing and addressed to the WHO Collaborating Centre for Drug Statistics Methodology.  Any user may in principle propose changes to ATC classifications. There is no application form for ATC alterations.

All proposals for changes 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 to change, 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: 2009-12-17