After preliminary study, Brazilian researchers advise against using high doses of chloroquine to treat patients with covid-19

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What we know about hydroxychloroquine against covid-19 2:23

(CNN) - A preliminary study conducted in Brazil on the use of chloroquine diphosphate to treat patients with symptoms similar to those of covid-19 ended early after the death of 11 patients, and researchers found that a high dose of the drug was associated with a severe type of arrhythmia or irregular heartbeat.

The study, which has not been peer-reviewed or published in a medical journal but was published on the medRxiv online medical server this Saturday, included 81 patients who were hospitalized with symptoms similar to those of covid-19 in Manaus, Brazilian Amazon. Patients enrolled in the study before receiving laboratory confirmation of covid-19.

For the trial, patients received a high dose of chloroquine, 600 mg twice daily for 10 days for a total dose of 12 g, or received a low dose of 450 mg for five days, twice daily only in the first day, for a total dose of 2.7g. All patients also received ceftriaxone and azithromycin as part of their treatment. A limitation of the study is that there were no patients who received a placebo.

On the sixth day of the trial, the researchers stopped the study early after some patients in the high-dose group died. Patients who were receiving a high dose of the drug then returned to the low dose.

The researchers wrote in their trial that while the chloroquine drug has been used safely for over 70 years for malaria, using it in high doses to treat covid-19 "could be toxic" and called for more research on the medicine.

"In conclusion, the high-dose CQ regimen (12g), given over 10 days, was not safe enough to warrant continuation of that particular study arm," the researchers wrote in the study, adding that They strongly recommend that this dose is no longer used for the treatment of severe covid-19.

The drug chloroquine is similar to hydroxychloroquine, but hydroxychloroquine has been called "a less toxic derivative" of chloroquine. President Donald Trump has touted these drugs as key pieces in the treatment of covid-19.

Currently, there is no treatment for covid-19 approved by the US Food and Drug Administration. But the agency has issued an emergency use authorization for chloroquine and hydroxychloroquine to treat hospitalized patients with covid-19.

Hydroxychloroquine