Start using ATC/DDD
How to start
When the decision to introduce the ATC/DDD methodology is taken, it is essential to realize that its proper use inevitably includes an important and time-consuming first step:
Each product has to be linked to the appropriate ATC code and DDD. For monitoring and comparing drug use internationally, it is important to ensure that the retrieved data are comparable, meaning that the ATC groups from different countries, regions or health facilities do have the expected content.
In order to achieve this, it is of vital importance that the officially correct ATC code is assigned to each medicinal product package. If possible, this work should be done on a national basis to secure consistent use of the methodology within a country. Many countries have established systems of unique identifiers for drug products at the package level. The number of DDDs per package should be calculated for each medicinal product package and this information should be added to the medicinal products registry. The national drug lists and ATC/DDDs should be linked at the level of the unique product identifier and this has to be done by persons with proper knowledge of the methodology.
A European Working Group made recommendations for setting up National Registers of Medicinal Products with validated ATC codes and DDD values in 2004. The document is available here .
Users should be aware of the ATC/DDD system as a dynamic system to which annual updates are made
A few alterations in ATC codes and DDDs usually occur annually and new ATC codes and DDDs are introduced every year. Thus it is necessary to check for updates in the drug list regularly: updates of the ATC/DDD Index are issued in January each year.
Historical sales data linked to specific packages no longer licensed or available should be kept. It is important to update the ATC codes and DDD values of historical utilization and expenditure data. Finally, when producing and presenting longitudinal trends in utilization and expenditure data, it is important that the data for different years are all presented using the latest ATC/DDD version.
Read more section
Important notes:
Medicinal substances are classified according to the main therapeutic or pharmacological use on the basic principle of only one ATC code for each medicinal product (as defined by route of administration and in some cases strength). This is an important principle for ATC classification as it allows aggregation of data in drug utilization studies without counting a medicinal product more than once. This principle is strictly handled by the caretakers so that users in different countries shall be able to classify a pharmaceutical product (defined by active ingredient/s, route of administration and strength) in the same way, even though it does not always match with the predominant use in every single country. ( Go to Chapter 1: ATC Classification and Challenges )
The coverage of the ATC system is not comprehensive. A major reason why a substance is not included is that no request has been received. A given country will nearly always have medicinal products and combination products for which no ATC codes or DDDs have been assigned. In these cases, it is important to consult the WHO Collaborating Centre for Drug Statistics Methodology in Oslo and request new ATC codes and DDDs. How to apply for new ATC codes and DDDs, see ATC codes and DDD codes.
For combination products, specific guidelines have been established for allocating ATC codes, these are explained in the Guidelines for ATC Classification and DDD assignment, click here .
To be able to compare drug utilization data from different countries and different periods, it is essential to know which version of ATC codes and DDDs are used. Since some changes in the ATC codes and DDDs are made annually, it is important to give proper references to the ATC/DDD versions used when presenting drug utilization figures.
Allocating DDDs to the products necessitates many of the same considerations as the allocation of the ATC code. However, in order to link the drug list with sales figures or prescription figures to obtain drug utilization statistics, it is necessary to make appropriate calculations such as the number of DDDs per drug package.