The US Food and Drug Administration (FDA) has revoked the emergency use authorisation (EUA) for antimalarials, chloroquine phosphate and hydroxychloroquine sulfate, to treat some hospitalised Covid-19 patients.

In March, FDA awarded the EUA for the use of these drugs donated to the Strategic National Stockpile when a clinical trial was not available or trial participation was not feasible.

According to the regulatory agency, chloroquine and hydroxychloroquine no longer meet the legal criteria for EUA.

Data from an ongoing analysis of the EUA and scientific research showed that the drugs are not likely to be effective against Covid-19 for the authorised EUA uses.

Also, based on the emerging data on serious cardiac adverse events and other potentially serious side effects, the known and potential benefits of the drugs no longer outweigh the known and potential risks for authorised use.

The Biomedical Advanced Research and Development Authority (BARDA) of the US Department of Health and Human Services originally filed for the EUA.

In consultation with the FDA, BARDA sent a letter asking the regulator to revoke EUA based on science and data available to date.

FDA Medical and Scientific Affairs deputy commissioner Anand Shah said: “We’ve made clear throughout the public health emergency that our actions will be guided by science and that our decisions may evolve as we learn more about the SARS-CoV-2 virus, review the latest data, and consider the balance of risks versus benefits of treatments for Covid-19.

“We will continue to examine all of the emergency use authorisations the FDA has issued and make changes, as appropriate, based on emerging evidence.”

The FDA noted that a large randomised clinical trial revealed no benefit on mortality or in speeding recovery when hospitalised patients were treated with hydroxychloroquine.

These results are consistent with other emerging data, including evidence that the suggested dosing regimens for the drugs are not likely to kill or inhibit SARS-Cov-2.