Drug utilization statistics for individual-level pharmacy dispensing data.

The emergence of large, computerized pharmacoepidemiologic databases has enabled us to study drug utilization with the individual user as the unit of analysis. A recurrent problem in such analyses, however, is the overwhelming volume and complexity of data. This paper reviews the methods to estimate basic epidemiologic measures of drug utilization and some methods to screen for aberrant prescribing patterns. It also presents the basis and application of the waiting time distributions that can provide information about the period prevalence, point prevalence, incidence, duration of use, seasonality and rate of prescription renewal or relapse for specific drugs. If analyzed regularly, these measures can disclose subtle trends in clinical drug use that would not be evident from the wholesale figures. In specific situations, pharmacy dispensing data without diagnostic information can be used to assess the association between drug use and adverse effects in a prescription symmetry design. Copyright 2005 John Wiley & Sons, Ltd.