April 14, 2020 / By Jacqueline Howard, Elizabeth Cohen, Nadia Kounang and Per Nyberg, CNN
(CNN) – Scientists around the world are continuing to study two drugs — chloroquine and hydroxychloroquine — for their potential as possible treatment approaches for illness caused by the novel coronavirus. Yet as new data emerge out of such research, so do some concerns about the efficacy and safety of the drugs when used to treat Covid-19.
There have been early indications that these drugs may be effective in treating or preventing Covid-19, but the medications haven’t endured the due diligence of extensive clinical trials and there have been growing concerns about the impact chloroquine and the closely related hydroxychloroquine can have specifically on the heart. 
Now, a chloroquine trial in Brazil has been cut short, hospitals in Sweden have been cautioned against using the drugs for Covid-19 and American cardiology groups have urged doctors to be aware of “potential serious implications” when used for people with existing cardiovascular disease.
‘First we do no harm’
The “safety profile” for chloroquine may differ from hydroxychloroquine overall but when it comes to the heart, there is no reason why one would be safer than another, said Dr. Paul Offit, director of the Vaccine Education Center and an attending physician in the Division of Infectious Diseases at Children’s Hospital of Philadelphia.
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 patients hospitalized with Covid-19.