Preventing drug interactions by online prescription screening in communitypharmacies and medical practices

Background: Drug interactions have been shown to be preventable by computer ized prescription entry and screening only in hospitals and not in communit y-based practice. Methods: We retrospectively evaluated the effect of online prescription scr eening in community pharmacies and physician offices of one health maintena nce organization, phased in during 3 consecutive 6-month periods in 1998 to 1999 (period I, system active only in 40% of pharmacies; period II, system active in 90% of pharmacies and 50% of physician offices; period III, syst em active in 95% of pharmacies and 90% of physician practices), on rates of prescriptions with-, patient exposure to-, and physician prescribing of po tential drug interactions. Findings: Cumulative data included 775,186 patients given at Least one pres cription, by one or more of 5504 physicians, whose prescriptions were dispe nsed at 572 pharmacies. Dispensing of drug interaction prescriptions was re duced by 21.1% and by 67.5% in periods II and III compared with period I (o dds ratio, 0.79; 95% confidence limit, 0.75-0.83 and odds ratio, 0.28; 95% confidence limit, 0.26-0.30, respectively). Patient exposure decreased only in those receiving 3 to 7 concurrent drugs (odds ratio, 0.80; 95% confiden ce limit, 0.71-0.90) with no reductions for patients who were given 2 drugs or 8 or more drugs. Only 19% to 25% of physicians wrote prescriptions for drugs that interact, but 85% of these repeated this pattern after being ale rted. The proportion of prescriptions of drugs that interact that originate d with a single prescriber, as opposed to 2 prescribers, decreased during t he 3 periods from 0.81 to 0.74 and 0.69 (P <.001). Interpretation: Computerized prescription entry and drug interaction screen ing in the community caused a 62.8% reduction in pharmacy-dispensed prescri ptions with severe drug interactions and a 20% reduction in patient exposur e to prescriptions with severe drug interactions; this reduction was negate d by polypharmacy of 8 or more drugs. The effect of interaction alerts on p hysician prescribing patterns was limited.