OBJECTIVES: Expensive medicines are often utilized when there are comparable alternatives available at a lower cost. Increasing prescriber awareness of medication cost at time of ordering may help promote cost-conscious use of medications in the hospital. Our objective was to evaluate the impact of cost messaging on the ordering of nine expensive medications. METHODS: This was a retrospective analysis of an institutional cost-transparency initiative in a 1,145-bed tertiary care academic medical center (The Johns Hopkins Hospital). Prescribers who ordered medications through the computerized provider order entry system at the Johns Hopkins Hospital. Each medication was compared to its pre-intervention baseline utilization dating back to January 1, 2013. For the seven medications with alternatives offered, we also analyzed use of the suggested alternative during these time periods. Interrupted time series and segmented regression models were used to examine prescriber ordering before and after implementation of cost messaging for nine high-cost medications. RESULTS: Following the implementation of cost messaging, no significant changes were observed in number of orders or ordering trends for intravenous formulations of eculizumab, calcitonin, levetiracetam, linezolid, mycophenolate, ribavirin, and levothyroxine. An immediate and sustained reduction in medication utilization was seen in two drugs that underwent a policy change in addition to the drug cost messages during our study, intravenous pantoprazole and oral voriconazole. Intravenous pantoprazole became restricted at our facility due to a national shortage (-985 orders per 10,000 patient days; p<0.001) and oral voriconazole was replaced with an alternative antifungal in oncology order sets (-110 orders per 10,000 patient days; p=0.001). CONCLUSIONS: Provider cost transparency alone did not significantly influence medication utilization at our institution. Active strategies to reduce ordering resulted in dramatic reductions of ordering.