Context: Retrospective drug utilization review is required of all state Medicaid programs and is performed by most private-sector prescription programs. However, it has not been shown to improve clinical outcomes or reduce the rate of potential prescribing errors, known as "exceptions." Objective: To look for an effect of retrospective drug utilization review on the rate of exceptions and of clinical outcomes in patients with an exception. Design, Setting, and Participants: Longitudinal ecologic study of the rate of exceptions, controlling for preintervention trends and calendar time; and a cohort study of all-cause and cause-specific hospitalizations in patients with an exception, controlling for potential individual-level confounders in 6 Medicaid programs using the same software in the mid-1990s. Main Outcome Measures: The rate of exceptions was examined as a function of retrospective drug utilization review implementation. In addition, before-after comparisons were made of the incidence of all-cause and cause-specific hospitalization in patients with exceptions. Results: We found no reduction in the rate of exceptions coincident with retrospective drug utilization review implementation (rate increase, 0.064 exceptions per 1000 prescriptions per month; 95% confidence interval [CI], -0.006 to 0.133). We also found no effect of retrospective drug utilization review on the incidence of all-cause hospitalization (odds ratio, 0.99;95% CI, 0.98-1.00) or cause-specific hospitalization. These results persisted in multiple subgroup analyses. Study states intervened using physician alerts in between 1% and 25% of exceptions. Conclusions: We were unable to identify an effect of retrospective drug utilization review on the rate of exceptions or on clinical outcomes. Given the lack of evidence for effectiveness, and suggestions from previous research of possible harm, policy-makers should consider withdrawing the legislative mandate for retrospective drug utilization review.
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