OBJECTIVES: To determine prescribers’ perceptions of near-real time messaging for potential drug-drug interactions (PDDIs) using a fax alert drug utilization review intervention. METHODS: This was a 6-month prospective study where a pharmacy benefit manager (PBM) distributed evidence-based summaries of 18 different PDDIs that included references and suggested management strategies. Fax alerts were individualized letters sent to the prescriber of the 2nd drug of a PDDI for an individual patient. A 16-item questionnaire to assess prescribers’ perceptions of the intervention accompanied each individualized PDDI evidence-based summary. Descriptive and multivariate logistical regression analyses were used to assess questionnaire responses. RESULTS: A total of 8075 fax alerts were distributed and 977 returned questionnaires, yielding a 12.1% response rate. 848 (86.8%) responses were completed by physicians and 71 (7.3%) completed by nurse practitioners. The most common PDDI fax alerts sent were for warfarin-statin (3511, 43.5%) and warfarin-thyroid (2111, 26.1%) interactions. 42.6% of respondents agreed or strongly agreed that fax alerts were a good way to communicate with them. A total of 37.5% of respondents, however, either agreed or strongly agreed that the fax alert was a “waste of my time.” 59.1% of respondents either disagreed or strongly disagreed that they would prefer to receive a telephone call when interactions like this occur. 50.5% indicated their computer system provided drug interaction alerts. When asked to evaluate the evidence-based information provided in the alert, carbamazepine-macrolide, ciprofloxacin-tizanidine, and statin-macrolide alerts were rated more favorable than other PDDIs. Prescribers who had received alerts and specialists were less likely to respond to the questionnaire (OR=0.685, p=<0.0001 and OR=0.851, p=0.0205, respectively). CONCLUSIONS: PBMs detect and notify prescribers of PDDIs during claims adjudication. This study found that some prescribers valued fax alerts, especially for less well-known PDDIs.  PDDI alert programs should carefully select PDDIs and other screening criteria to ensure prescribers respond to messaging.