Isaksen et al., medRxiv, doi:10.1101/2020.06.19.20135475 (Preprint) Chloroquine, but not hydroxychlorquine, prolongs the QT interval in a primary care population
Safety analysis in patients without COVID-19, finding a small increase in QTc associated with use of CQ, but not HCQ. Authors also study mortality (n=3,368), with HCQ hazard ratio 0.67 [0.43-1.05].