ObjectiveTo present a new dexamethasone mouthwash formulation and analyze its effectiveness and safety among patients receiving stomatitis-producing antineoplastic agents. MethodProspective observational study conducted in a university hospital between March 2017 and November 2019. Consecutive patients starting everolimus were enrolled. Patients were instructed to rinse dexamethasone mouthwash formulation twice daily until discontinuation of everolimus. A second cohort of patients with existing stomatitis induced by high probability of producing stomatitis chemotherapy therapies was also recruited to assess treatment effectiveness. Effectiveness and safety of dexamethasone mouthwash formulation was assessed. ResultsDexamethasone mouthwash formulation was prescribed in nine patients as prophylaxis. Six patients were diagnosed with breast cancer, two with neuroendocrine tumor and one with renal cell carcinoma. Four patients developed mild stomatitis (grade 1-2) and three patients discontinued everolimus due to other treatment-related adverse events. In addition, dexamethasone mouthwash formulation was prescribed as treatment in five patients with existing stomatitis. All patients achieved a significant reduction in the severity of stomatitis after starting the dexamethasone mouthwash formulation. In both cohorts, dexamethasone mouthwash formulation was well tolerated and neither dose reduction nor discontinuation related to stomatitis was required. ConclusionsDexamethasone mouthwash formulation could be considered as a suitable alternative for stomatitis management.