Prescription dispensing data were obtained from the database maintained by the DUSC that monitors the dispensing of prescription medicines through community pharmacies in Australia.2 No data on public hospital use are included in this database. The measurement units used are either prescription volumes or the number of defined daily doses (DDDs) per 1000 population per day. The DDD is based on the assumed average daily dose of the drug when used for its main indication by adults. It is the unit approved by the World Health Organization (WHO) for drug use studies, and allows for comparisons independent of differences in price, preparation and quantity per prescription.3 Within the data on dispensing of antidepressant drugs subsidised by the Pharmaceutical Benefits Scheme (PBS), it is also possible to determine the major specialty of the prescribing doctor.
Data on total sales of antidepressants from wholesalers to retail and hospital pharmacies for all countries, except Sweden, were obtained from IMS Health Incorporated. IMS Health is the leading international provider of information on drug usage to the pharmaceutical and healthcare industries.4 Data were retrieved as kilograms of active ingredient and then converted to DDDs per 1000 population per day. Excluded were the use of lithium, Hypericum (St John’s wort) or tryptophan, and combinations involving these drugs or their active constituents. Utilisation data for Sweden, where separate local arrangements apply, were supplied by the Swedish Association of the Pharmaceutical Industry (LIF).
The 1999 WHO defined daily doses (DDDs) were used in calculations. Drugs unique to particular markets that did not have DDDs available were provisionally assigned values using standard references and information provided by drug information centres in the countries involved.5
Prescriber surveys
Information related to general practice patient encounters for depression was obtained from the General Practice Statistics and Classification Unit of the Family Medicine Research Centre (FMRC), University of Sydney, which is conducting an ongoing survey of service provision by general practitioners (GPs).6 This involves 1000 randomly selected, active, recognised GPs per year, each recording details of 100 consecutive consultations on structured encounter forms. Rolling recruitment ensures that the recording weeks are distributed evenly over the year and that there is constant change in participants. These data can be compared with the findings of an earlier FMRC study of morbidity and treatment in general practice that used simpler but compatible methods.7 Information on prescribing by specialists is not included in these GP surveys.