[Individual-based statistics on drug utilization]

The Danish retail pharmacies' drug subsidy system is completely computerised. The data are person-identifiable, making it possible to chart the population's drug use from the perspective of the individual users. We undertook an analysis to explore the potential of this data source and to analyse the heavy drug users specifically. The analysis encompassed all 890,352 prescriptions presented by Odense citizens in 1991. There was a total sales volume of 32 million defined daily doses, consumed by 113,468 adult drug users, corresponding to 65.1% percent of the adult population. We found 2388 heavy drug users defined by an annual purchase of more than 2000 defined daily doses. Heavy drug users accounted for 1.4% of the adult population and 22.9% of drug sales. Heavy drug users were remarkably well characterised by their main therapeutic class which constituted a median of 47% of their drug use. A median of 97% of each heavy user's drugs were issued by one main prescriber. We conclude that heavy drug use generally can be ascribed to severe disease rather than to irresponsible prescribing. For the most important drug classes, we present various epidemiological measures of drug use, including one-year prevalence, incidence, duration of therapy and some measures of skewness in utilization. If analysed regularly these measures can disclose subtle trends in clinical drug use that would not be evident from the wholesale figures.