New approaches to analysing prescription data and to transfer pharmacoepidemiological and evidence‐based reports to prescribers

Pharmaceuticals represent a significant cost driver within health-care systems of all industrialised countries and all National Health Systems (NHS) are facing the problem of the pharmaceutical governance. In Italy, drug expenditures in general practice (prescription) during 2001 reached 12 919 million Euro (s) which means around 200s per capita, approximately 16% of public health expenditure. By the end of 2001, the drug reimbursable expenditure had increased by 32% over that of 2000. Prescribing indicators for general practice, measuring volume and cost of drug utilisation, have been proposed by the NHS for over two decades and are likely to have a central role in the clinical governance activities of many primary care groups. Data on drug utilisation are now available in several countries from various sources. Defined Daily Dose (DDD) statistics allow comparison among countries and even across different formularies. Furthermore, for chronic diseases, DDD can be a proxy for exposure or prevalence of drug treatments and they have also become a standard for comparing the therapeutic behaviours of physicians in different countries. For several groups of drugs, the DDD methodology has been demonstrated to be valuable in describing overall therapeutic profiles. However, the DDD, as a technical unit of measurement, is not necessarily equivalent to average doses actually prescribed nor to different or complementary approaches, such as prescribed daily doses (PDD). Other measures proposed are drug utilisation 90% and therapeutic courses, that may give further insight to drug prescribing patterns. Although valuable, DDD statistics themselves provide only a rough idea of the variations in expenditure that are so important for developing budgets, e.g. the relative weight of quantity prescribed, price variations and mix effects. Usually, the fluctuations in drug expenditure are reported through price and general quantity (as number of packages) indicators. However, this does not take into account the variation produced by new drugs licensed, new formulations as well as the shift towards more expensive products. Thus, quantity, price and the variation due to the shift within the same therapeutic group of drugs towards more or less expensive products (‘mix effect’) may represent the three main driving factors for drug expenditure variations (Figure 1). In Italy, a working group on pharmacoepidemiology, which involved the Italian National Drug Utilisation Monitoring Centre (Os.Med), the National Institute of Health Care (I.S.S) and a Centre for the Evaluation of Effectiveness of Health Care (Ce.V.E.A.S), has developed a new approach to separate quantity, price and mix effects using DDDs. Prescription data from all 16 000 Italian retail pharmacies—available through the Italian National Drug Utilisation Monitoring Centre since 1999—have been used to calculate expenditure variations according to quantity (expressed in DDD), prices (Laspeyres index) and mix effects (within the same drug group). In order to appreciate the impact of the above mentioned components on drug expenditure, we used the formula reported in the Figure 1 where: