The Committee recognized the importance of drug utilization studies. WHO recommends that such studies be conducted using the Anatomical Therapeutic Chemical (ATC) classification system and the Defined Daily Dose (DDD) as a measuring unit (31). The purpose of the ATC/DDD system is to serve as a tool for drug utilization re-search in order to improve the quality of drug use. Access to standardized and validated information on drug use is essential to allow audit of patterns of drug utilization, identification of problems, and monitoring of the outcomes of educational or other interventions.
The ATC classification system was originally developed and is maintained by the WHO Collaborating Centre for Drug Statistics Methodology. The model list has recently been classified using the ATC system and is available on request from the Collaborating Centre .
 For further information, contact the WHO Collaborating Centre for Drug Statistics Methodology, PO Box 100, Vietvet, N-0518 Oslo, Norway. (Tel.: +47 22169811; fax: +47 22169818; e-mail: firstname.lastname@example.org.)