"It is no longer reasonable to believe that the oral formulas HCQ (hydroxychloroquine) and CQ (chloroquine) are effective in treating covid-19," wrote Denise Hinton, chief scientist at the Food and Drug Administration (FDA) in a letter.

"It is also not reasonable to believe that the known and potential benefits of these products exceed their known and potential risk," he said in announcing the end of their emergency use.

The FDA had given the green light on March 30 for these antimalarial treatments to be prescribed, only in hospitals, to patients infected by the new coronavirus.

Donald Trump placed high hopes on hydroxychloroquine, the efficacy of which against covid-19 was never demonstrated with rigorous arguments.

"There is a good chance it could have a big impact. It would be a blessing if it worked," the magnate had noted.

The Republican president himself later underwent preventive treatment with hydroxychloroquine for two weeks.

But the FDA warned April 25 against using the two antimalarials "outside of a hospital or clinical trial because of the risk of heart rhythm disorders."

France, where a controversial doctor, Professor Didier Raoult, defended and highlighted hydroxychloroquine, banned its use on May 28 in treatment against coronavirus.