The use of the world health organisation anatomical therapeutic chemical/defined daily dose methodology in Canada

Drug utilization studies can provide useful information to improve the appropriate and effective use of pharmaceuticals in populations. Using common drug utilization evaluation systems can facilitate national and international comparisons of drug use, examine trends in use over time, and compare drug use to best practice. Limited work has been done in Canada to compare drug use across jurisdictions (provinces, regions) or with other countries. In order to make such comparisons, a common framework is needed. The World Health Organisation (WHO) Anatomical Therapeutic Chemical classification and Defined Daily Dose measure for studying drug utilization in Canada is explained, highlighting advantages of and considerations with use of this methodology. Examples of Canadian studies using this methodology are provided. In linking the Anatomical Therapeutic Chemical/Defined Daily Dose with each marketed drug's unique identifier (the Canadian Drug Identification Number), researchers in Canada have a tool for measuring drug utilization among regions, countries, and time periods.