A Brazilian study that saw 81 coronavirus patients given chloroquine was ended early after some of them developed irregular heart rates, according to The New York Times. Chloroquine is closely related to hydroxychloroquine, which President Trump has promoted as a potential treatment for the novel coronavirus despite little evidence of its efficacy. The Brazilian study in the city of Manaus saw half the study participants given a dose of 450 milligrams of chloroquine twice daily for five days, while the rest were prescribed a higher dose of 600 milligrams for 10 days. Within three days, researchers started noticing heart arrhythmias in patients taking the higher dose. By the sixth day of treatment, 11 patients had died, leading to an immediate end to the high-dose segment of the trial. The researchers said the study did not have enough patients in the lower-dose portion of the trial to conclude if chloroquine was effective in patients with severe disease.