'Serious poisoning and death have been reported after mistaken use of a chloroquine product not intended to be taken by humans,' the regulator said NEW DELHI: The US Food and Drug Administration (FDA) has issued a caution against the use of repurposed anti-malarial drug hydroxychloroquine for the treatment of Covid-19 outside of a hospital or a clinical trial due to the risk of heart rhythm problems. “Hydroxychloroquine and chloroquine have not been shown to be safe and effective for treating or preventing Covid-19," the US drug regulator said, adding that it is aware of reports of serious heart rhythm problems in Covid-19 patients being treated with either drugs, often in combination with azithromycin and other QT prolonging medicines. “P