581. Risks versus Benefits of Metronidazole Use for the Prevention of Acute GVHD in Allogeneic Stem Cell Transplant Recipients

BACKGROUND: Currently, acute graft versus host disease (aGVHD) prophylaxis in hematopoietic stem cell transplants (HSCT) varies amongst different institutions. There is a lack of data supporting the use of metronidazole for aGVHD prophylaxis in HSCT. To further investigate if metronidazole has an effect on aGVHD, allogeneic HSCT recipients will be examined to determine if metronidazole post-transplantation decreases the incidence of aGVHD and the risks of adverse drug events (ADE) associated with this practice. METHODS: This retrospective study included 120 adult patients who received an allogeneic HSCT between January 1, 2010 to December 31, 2013. The primary endpoint is the incidence of aGVHD, defined as within 100 days post-transplant. Secondary endpoints include the rate of metronidazole discontinuation due to intolerance, frequency of metronidazole-related adverse effects, incidence of Clostridioides difficile infection, mortality, and overall survival. RESULTS: One hundred six patients met the inclusion criteria. The majority of patients received metronidazole (88 vs. 18). Less patients in the metronidazole arm developed aGHVD (51.1% vs 61.1%, p=0.44). In the subcategories of liver, skin, and gastrointestinal aGHVD, patients who received metronidazole developed less gastrointestinal aGVHD (26.1% vs 50.0%, p=0.045). Gastrointestinal ADEs were the most common metronidazole-related ADEs (19.3%, Table 1). There were no significant differences in the incidence of C. difficile infection, mortality, and overall survival between the two arms (Table 2). Table 1. Adverse Drug Events and Discontinuation of Therapy [Image: see text] Table 2. Additional Secondary Outcomes [Image: see text] CONCLUSION: Despite a reduction in gastrointestinal aGVHD in the metronidazole arm, approximately one in four patients experienced an ADE to the medication, likely due to the prolonged use of the medication (33 days). The utilization of post-transplant cyclophosphamide for GVHD prophylaxis likely eliminates the need for metronidazole; however our findings suggest a benefit in preventing gastrointestinal aGVHD with metronidazole; albeit, caution is warranted given the high incidence of ADE associated with prolonged use. DISCLOSURES: All Authors: No reported disclosures