Combined use of hydroxychloroquine and azithromycin was globally adopted, in part due to paucity and high cost of alternative therapies. However the utility of these medications has been questioned; and thus safety becomes a major concern given clinical equipoise regarding efficacy. Both hydroxychloroquine and azithromycin continue to be administered in US clinical trials examining their potential role in prevention of infection, treatment of mild infection in ambulatory patients, and in combination with other medical regimens in treatment of patients with severe disease. These drugs also continue to be clinically utilized in hospitalized patients around the globe, often without continuous telemetry due to lack of resources. Concern regarding use of hydroxychloroquine without adequate rhythm monitoring in clinical trials has been recently expressed.1 A review of clinicaltrials.gov at the time of submission of this correspondence reveals actively recruiting trials of combined hydroxychloroquine/azithromycin with or without additional COVID-19 therapies, for both ambulatory and hospitalized patients within and outside the US. The potential for hydroxychloroquine and azithromycin to cause QT prolongation is counterbalanced by very low risk of pro-arrhythmia in the general population, and emerging evidence of relatively low risk of Torsades de Pointes (TdP) in COVID-19 patients.2,3,4,5 Thus delineation of the determinants of significant QTc prolongation and pro-arrhythmic risk for hydroxychloroquine/azithromycin is very important, especially given mounting evidence of inefficacy in COVID-19 treatment.