Using a computerized drug prescription screening system to trace drug interactions in an outpatient setting.

Background: Drug-drug interactions are one of the main causes of adverse effects. These events have been studied most often in hospital settings; however, investigations on prescribing based on community practice have shown a high prevalence rate of potential drug interactions.
Objective: To develop a computerized system able to trace drug interactions quickly through the identification of clinicians issuing potentially unsafe prescriptions.
Methods: We retrospectively evaluated hazardous concomitant prescriptions of hydroxymethylglutaryl coenzyme A reductase inhibitors (statins) and azole antifungals, which were invoiced through 9 months of 2001 within an outpatient setting. The study was conducted in Badajoz, a southern Spanish province, and was divided in three 3-month periods according to the release of 2 warning notes on this drug combination by the Spanish Drug Agency. Prescriptions written during this period were optically scanned each month, and the resulting information, including data from patients, physicians, and drugs involved, was converted to a database and searched for potentially unsafe coprescriptions.
Results: A total of 8342711 prescriptions were invoiced in the period of study, 174 of which were for a statin-azole combination. The number of these prescriptions remained fairly constant during periods I and II (63 and 71, respectively), decreasing to 40 in period III. Some clinicians (12.6%) repeatedly prescribed a hazardous drug combination at some point in this study, whereas 18 of 171 patients who received the hazardous coprescription at any time did so repeatedly within a given period. The impact of drug alerts was remarkably deeper in urban rather than rural care centers.
Conclusions: The computerized drug prescription handling system described here is able to readily identify physicians and patients who issue/consume hazardous drug combinations, thus allowing both the possibility of individually informing the healthcare professionals involved and early detection of adverse effects.