Medicine utilization data have a central role in the quality of care cycle, and are essential to manage policy related to medicine supply, pricing, cost and use. The anatomical therapeutic chemical (ATC) and defined daily dose (DDD) methodologies for classification and measurement can be helpful in following and comparing trends in cost, but need to be used with caution. Basing detailed reimbursement, therapeutic group reference pricing, and other specific pricing decisions on the ATC and DDD assignments is a misuse of the system.

The purpose of the ATC/DDD system is to serve as a tool for medicine utilization research in order to improve quality of medicine use. One component of this is the presentation and comparison of medicine consumption statistics at international and other levels.

A major aim of the WHO Collaborating Centre for Drug Statistics Methodology and Working Group is to maintain stable ATC codes and DDDs over time to allow trends in medicine consumption to be studied without the complication of frequent changes to the system. There is a strong reluctance to make changes to classifications or DDDs where such changes are requested for reasons not directly related to medicine consumption studies. For this reason the ATC/DDD system by itself is not suitable for guiding decisions about reimbursement, pricing, and therapeutic substitution.

The classification of a substance in the ATC/DDD system is not a recommendation for use, nor does it imply any judgments about efficacy or relative efficacy of medicines and groups of medicines.

Text in this section taken from the WHO Collaborating Centre for Drug Statistics Methodology Web site at