The U.S. Food and Drug Administration recently revoked the emergency use authorization for malaria drugs chloroquine and hydroxychloroquine, citing severe adverse events and other harmful side effects, the CBS News reports. 

The federal agency concluded that the drugs were not effective at preventing the coronavirus after reviewing a study published in the New England Journal of Medicine. Results showed that hydroxychloroquine did not do any better than placebo treatments. FDA officials claimed the potential benefits could not outweigh the risks, including dangerous abnormalities in heart rhythms.

According to the New York Times, the review revealed severe heart disorders occurred in 100 cases of patients taking the drugs-25 of which were fatal. The researchers also found 113 instances where anti-malarial drugs led to liver abnormalities, kidney problems, and renal diseases. Four patients also developed methemoglobinemia-a blood disorder that prevents oxygen from getting to cells.

However, Alex M. Azar II-the secretary of health and human services-claimed the revocation of the emergency use approval only took away the authorization for hospitals to use federal stockpiles of hydroxychloroquine. Doctors are still allowed to prescribe the drugs, he said.

Remdesivir

On Monday, the FDA released a warning that COVID-19 patients taking both the anti-malaria and antiviral drug Remdesivir could weaken the effectiveness of the latter treatment.

In a report by CNBC, the FDA will release a revised fact sheet for health-care providers claiming the co-administration of chloroquine or hydroxychloroquine and remdesivir could reduce the antiviral activity of the latter.

Controversies and Timeline

In March, the FDA allowed medical institutions to use chloroquine and hydroxychloroquine to treat COVID-19 patients after several laboratory tests conducted in the early days of the pandemic showed the drugs, specifically hydroxychloroquine, interfered with the coronavirus pandemic's ability to enter healthy cells.

However, the reports came from small studies that did not stand up well to more extensive studies, as reported by NPR. Dr. Peter Lurie, the president of the Center for Science in the Public Interest, said evidence from completed clinical trials show the drug is not effective against the virus.

In April, Rick Bright-the director of the health department's biomedical research unit-claimed he was removed from his post after he pushed for rigorous vetting of the anti-malaria drug that the government touted.

In a statement, Bright alleged the government pressured him to direct money to hydroxychloroquine and believed his transfer was in response to his insistence that funds be allocated into scientifically vetted solutions to the virus.

Anti-malaria drugs garnered much attention and excitement earlier in the pandemic after U.S. President Donald Trump championed the drug during multiple press conferences.

His support for the drug was echoed by Brazil's President Jair Bolsonaro, who also promoted the unproven treatment. Bolsonaro reportedly ordered the mass production of hydroxychloroquine in Brazil's military pharmaceutical laboratory. Bolsonaro's government also received over two million doses from the White House in mid-May.

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