The Food and Drug Administration said on Monday that it was revoking emergency authorization of two malaria drugs to treat Covid-19, saying that they are “unlikely to be effective.”
The drugs, hydroxychloroquine and chloroquine, were heavily promoted by President Trump after a handful of small, poorly controlled studies suggested that they could work in treating the disease. Mr. Trump said he took hydroxychloroquine after he had been exposed to two people who tested positive for the coronavirus.
The agency said that after reviewing some data, it determined that the drugs, particularly hydroxychloroquine, did not demonstrate potential benefits that outweighed their risks. Earlier this spring, the F.D.A. had also issued a warning that the drugs could cause dangerous heart arrhythmias in Covid patients.
In March, the F.D.A. authorized stockpiles of the drugs, which had been donated by pharmaceutical companies, to be used in hospitals to treat patients with the virus. But in a letter on Monday revoking the authorization, the agency said that further studies had shown that the two drugs were unlikely to be effective in stopping the virus, and that national treatment guidelines didn’t recommend using them outside of clinical trials.
According to the letter, written by Denise M. Hinton, the F.D.A.’s chief scientist, the request to revoke the authorization came from the Biomedical Advanced Research and Development Authority, the unit of the Department of Health and Human Services that had initially asked for the authorization.
In April, the head of that unit, Dr. Rick Bright, said he was removed from his post after he pushed for rigorous vetting of hydroxychloroquine, even as Mr. Trump and his allies were enthusiastically promoting the drug.
The use of hydroxychloroquine spiked after Mr. Trump continuously praised its potential, calling it a possible “game changer” and saying, “What the hell do you have to lose?” His repeated promotions during daily briefings at the White House prompted runs on pharmacies, threatening supplies for the drugs, which are also taken by people with rheumatoid arthritis and lupus.
But interest in hydroxychloroquine has waned in recent weeks as further studies showed that the drug did not appear to be effective in treating or preventing Covid-19. Earlier this month, a study of 821 people who had been exposed to patients infected with the virus showed that the drug did not prevent infection.
In May, an article in the Lancet about another study concluded that hydroxychloroquine and chloroquine did not help patients and may have harmed them — but that study was later retracted after the authors could not verify the database of medical records on which the article was based.
Several trials of hydroxychloroquine are still underway, including additional studies of whether it can be used to prevent coronavirus infection. The World Health Organization resumed a study of the drug after briefly halting it in the wake of the Lancet article. And it is still being embraced elsewhere, including in Brazil, which is battling an explosive outbreak.
Members of Congress have questioned increases in the F.D.A.’s granting of emergency use authorizations during the pandemic for certain drugs as potential treatments. They have also questioned authorizations for antibody and diagnostic tests whose data had not been thoroughly vetted before approval, and for certain types of masks and other devices. Some Democratic lawmakers have criticized the Trump administration for pressuring the agency into issuing too many emergency approvals.