The FDA issued a drug safety communication to remind healthcare professionals and patients of the known risks associated with both hydroxychloroquine and chloroquine. These antimalarial treatments have not been shown to be safe and effective for treating or preventing COVID-19. Hydroxychloroquine and chloroquine can cause abnormal heart rhythms such as QT interval prolongation and a dangerously rapid heart rate called ventricular tachycardia. To decrease the risk of these life-threatening heart problems, FDA is warning the public that hydroxychloroquine and chloroquine use should be limited to clinical trials in hospital settings. Read the FDA safety alert.