WASHINGTON, DC, United States (AP) — US regulators yesterday revoked emergency authorisation for malaria drugs promoted by President Donald Trump for treating COVID-19, amid growing evidence they don't work and could cause serious side effects.

On Thursday, a National Institutes of Health (NIH) panel of hyrdoxychloroquine experts revised its recommendations to now specifically recommend against the drug's use except in formal studies, and “that, I'm sure, had influence on the FDA,” Nissen said.

The actions by FDA and NIH send a clear signal to health professionals against prescribing the drugs for coronavirus.

The FDA granted emergency use of the drugs for coronavirus patients in late March at the same time the US Government accepted 30 million doses of hydroxychloroquine and chloroquine that had been donated by two foreign drug manufacturers.

Rick Bright said he worked with FDA senior staff to limit the drugs' authorisation to patients hospitalised with COVID-19 and under professional supervision.