Guidelines for ATC classification and DDD assignment - WHOCC

I. INTRODUCTION
A. History of the ATC/DDD system
The field of drug utilization research has attracted increasing interest since its
infancy in the 1960s. The pioneering work was done by two consultants at the
WHO Regional Office for Europe, Engel and Siderius (The consumption of drugs:
report of a study 1966-1967. WHO regional Office for Europe, 1968). Their study
of drug consumption in six European countries during the period 1966-1967
showed great differences in drug utilization between population groups. This study
was followed by a symposium in Oslo in 1969 entitled The Consumption of Drugs,
organised by the WHO Regional Office for Europe. It was agreed at this
symposium that an internationally accepted classification system for drug
consumption studies was needed. It was also at this symposium that the Drug
Utilization Research Group (DURG) was established and tasked with the
development of internationally applicable methods for drug utilization research.
By modifying and extending the European Pharmaceutical Market Research
Association (EphMRA) classification system, Norwegian researchers developed a
system known as the Anatomical Therapeutic Chemical (ATC) classification.
In order to measure drug use, it is important to have both a classification system
and a unit of measurement. To deal with the objections against traditional units of
measurement, a technical unit of measurement called the Defined Daily Dose
(DDD) to be used in drug utilization studies was developed. The ATC/DDD
system has been used in Norway since the early seventies for presenting drug
consumption data.
The Nordic Council on Medicines (NLN) established in 1975, collaborated with
Norwegian researchers to further develop the ATC/DDD system. The NLN
published the Nordic Statistics on Medicines using the ATC/DDD methodology for
the first time in 1976. Since that time the ATC/DDD system has expanded to
include most drugs on the Nordic market. At the same time, international interest
in the ATC/DDD system for drug utilization research expanded beyond the Nordic
countries largely through the activities of the DURG who recommended the
ATC/DDD methodology for international drug utilization studies.
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