Hsu CD, et al. - Given that concomitant hydrochlorothiazide and cyclophosphamide use has been listed as a potential major drug-drug-interaction (DDI) in Micromedex, which is a pharmacy reference database, however, this claim is supported by merely one small, single center study, therefore, researchers performed this study with a cohort of women with breast cancer starting adjuvant chemotherapy comprising cyclophosphamide in order to estimate the links between this potential DDI and two adverse chemotherapy-related events, neutropenia-related hospitalizations and treatment regimen discontinuation. For this purpose, they used linked Surveillance, Epidemiology, and End Results program (SEER)-Medicare data. They found exposure to concomitant hydrochlorothiazide in 27% of women taking cyclophosphamide therapy. Among these, a neutropenia-related hospitalization and treatment regimen discontinuation prior to completion happened in 11% and in 21%, respectively. Overall, a link between concomitant hydrochlorothiazide use and two clinically important adverse chemotherapy-related events was not supported by the findings.