A small Brazilian study on the effects of the anti-malaria drug chloroquine, which is similar to the drug that President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE has touted as a possible "game changer" in treating the coronavirus, was abruptly halted because some patients taking high doses developed irregular heart rates generating "safety hazards."

The findings were revealed in a study funded by the Brazilian state of Amazonas and published on Saturday in medRxiv, an online server for medical articles, The New York Times first reported.

Chloroquine is similar to hydroxychloroquine, the drug Trump has repeatedly touted. Health experts have insisted that not enough is known about either drug to determine its efficacy in combating COVID-19.

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The Brazilian study included 81 hospitalized patients, with about half being given a 450 milligram dose of chloroquine twice on the first day of the study followed by one daily 450 milligram dose for four more days.

The other participants were prescribed a dose of 600 milligrams twice daily for 10 days.

Patients taking higher doses experienced heart arrhythmias, or improper beating of the heart, within three days, according to the study. Eleven patients died by the sixth day of treatment and caused the research on high-dosages to end.

"Preliminary findings suggest that the higher CQ dosage (10-day regimen) should not be recommended for COVID-19 treatment because of its potential safety hazards," the study's abstract said. "Such results forced us to prematurely halt patient recruitment to this arm."

The lower-dosage portion of the study did not include enough patients to gauge whether it is effective in treating severely ill patients, the Times noted. The researchers said that more studies assessing the efficacy of chloroquine are "urgently needed."

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The researchers said that the study would prove useful given the global push to use anti-malaria drugs to treat COVID-19, providing "updated COVID-19 patient management recommendations." The study was published in medRxiv before being peer-reviewed, the Times noted.

There is no known cure for COVID-19. While Trump and some of his allies have repeatedly promoted the use of hydroxychloroquine, health experts such as Anthony Fauci Anthony FauciOvernight Health Care: CDC reverses controversial testing guidance | Billions more could be needed for vaccine distribution | Study examines danger of in-flight COVID-19 transmission Trump claims enough COVID-19 vaccines will be ready for every American by April Gates says travel ban made COVID-19 worse in US MORE, the government's top infectious disease expert, warn that there isn't enough data to show if it works.

The Centers for Disease Control and Prevention notes on its website that hydroxychloroquine, which is also used to treat lupus, and chloroquine are "under investigation in clinical trials for pre-exposure or post-exposure prophylaxis of SARS-CoV-2 infection, and treatment of patients with mild, moderate, and severe COVID-19."

The Food and Drug Administration in late March issued an emergency use authorization for the anti-malaria drugs, noting it would allow more than 30 million doses of the drugs to go to the Strategic National Stockpile.

Correction: This story was updated April 14 at 3:33 p.m. to correct the dosage levels in the administered study.