In the study that looked at over 96,000 people hospitalised with Covid-19, those treated with hydroxychloroquine or the related chloroquine had higher risk of death than patients who were not given the medicines.
Mehra's group analyzed some 96,000 patients from 671 hospitals on six continents with COVID-19 infection, from December 20 to April 14, all of whom had either died or been discharged from the hospital by April 21.
An worldwide research team led by the University Hospital of Zurich and Harvard Medical School finds the controversial antimalarial drugs, hydroxychloroquine and a similar drug chloroquine, show no benefit against Covid-19.
While the study found an increased risk of in-hospital mortality, the relationship between death and ventricular tachycardia, or the lower chambers of the heart beating quickly, wasn't studied, the doctors said.
According to the worldwide news agency, The death rates of the treated groups were: hydroxychloroquine 18%; chloroquine 16.4%; control group 9%.
The team compared outcomes from patients treated with chloroquine alone (1,868), hydroxychloroquine alone (3,016), chloroquine in combination with a macrolide (3,783) or hydroxychloroquine with a macrolide (6,221).
About 9% of patients taking none of the drugs died in the hospital, versus 16% on chloroquine, 18% on hydroxychloroquine, 22% on chloroquine plus an antibiotic, and 24% on hydroxychloroquine plus an antibiotic.
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After taking into account many factors, including age, race, gender and basic health conditions, the risk of mortality among patients taking hydroxychloroquine increased by 34%, and the risk of serious heart arrhythmia - by 137%.
The biggest increase was seen in the group treated with hydroxychloroquine in combination with a macrolide, where 8% of patients developed a heart arrhythmia (502/6,221) compared with 0.3% patients in the control group (226/81144).
"It is clear that high-profile endorsements for taking these drugs without clinical oversight is both misguided and irresponsible". About 14,000 of which received one of four drug cocktails that included chloroquine or hydroxychloroquine. The Food and Drug Administration (FDA) has previously warned against the use of the drug outside of hospital settings after receiving reports of "serious heart rhythm problems".
Trump's criticism of the studies also comes as his allies have been eager to counter messaging from public health experts who say Trump is putting lives at risk by pushing states to quickly reopen in an election year.
Researchers are searching through available options to treat the coronavirus, which has killed more than 330,000 people, including drugs like the antimalarials that are also already approved to treat lupus and rheumatoid arthritis.
The Lancet study authors suggested the medicines should not be used to treat Covid-19 outside of clinical trials until those studies confirm their safety and efficacy for Covid-19 patients.
As President Donald Trump pushes to reopen the country despite warnings from doctors about the consequences of moving too quickly during the coronavirus crisis, he has been lashing out at scientists whose conclusions he doesn't like. "In the meantime, we suggest these drugs should not be used as treatments for Covid-19 outside of clinical trials". Christian Funck-Brentano, of Sorbonne University in Paris, wrote in a journal commentary accompanying the new study.