The Food and Drug Administration issued a warning about the antimalarial drugs after it became aware of reported heart risks.
Both have been embraced by Trump and others as a potential COVID-19 treatment. President Donald Trump emphatically defended himself Tuesday against criticism from medical experts that his announced use of a malaria drug against the coronavirus could spark wide misuse by Americans of the unproven treatment with potentially fatal side effects.
Trump's revelation a day earlier that he was taking hydroxychloroquine caught many in his administration by surprise and set off an urgent effort by officials to justify his action.