The computerisation of community pharmacy prescription records has resulted in the production of a wealth of largely untapped information about pharmaceutical services delivery. At the same time, software was developed that allowed electronic mapping of geographic information. We present the findings from a series of studies designed to explore the potential of using Geographic Information Systems (GIS) technology to analyse community pharmacy prescription databases with a view to improving understanding of:

• client location and loyalty
• geographic and socio-economic variation in prescribing patterns between and within therapeutic classes and by prescriber
• access to pharmaceutical services in the community
• documentation and monitoring of the distribution of prescription medicines on a national basis

In the first study, the addresses of prescription customers were downloaded from twelve community pharmacies throughout New Zealand and electronically matched (geocoded) against a geographic reference database. It was found that central city pharmacies had a broad scattering of low-density clientele throughout the city with few customers living in the immediate vicinity. Suburban pharmacies drew their clients in large numbers from the surrounding residential suburbs. Rural pharmacies' customers came from the town (high density) and surrounding countryside (low density) with some travelling substantial distances. In the second study, the names and addresses of prescription customers were downloaded, combined and sorted by surname for 72% of the pharmacies in one region. These were cross-matched to show the proportion of customers who visited one, two or more pharmacies. Just over half (54%) of all pharmacy prescription customers were loyal to one pharmacy. Although only 0.5% of customers visited six or more pharmacies this represented over 500 people in two years in the region studied. Customer loyalty patterns have implications for levels of care, with the possibility that, for those customers visiting many pharmacies, no pharmacist has a complete overview of a customer's medication history. In the third study, the entire database of one community pharmacy for one year was downloaded and tables within it cross-linked to enable us to map the distribution and frequency of dispensing of any particular drug or class of drugs from that pharmacy. The addition of socio-economic data, in the form of NZ Deprivation Index scores, enabled us to say something about the socio-economic status of those sectors of the population who have received various medicines. The fourth study, using the same technologies, was designed to map access to pharmaceutical services by both distance from the pharmacy and socio-economic status of the client. Buffer zones representing varying distances from each pharmacy were created. Determining the population inside or outside a zone is one way of quantifying access to services. Ethical issues not withstanding, national data could potentially be collected via access to all community pharmacy databases. Electronic prescribing, incorporating National Health Index data, offers one means of standardising data with respect to medicines and health services access and utilisation. Similarly, electronic information has the potential to tell us who is taking what medicines and what the effects of pharmaceuticals are on secondary care costs.