(CNN) -- President Donald Trump claimed Monday he is taking hydroxychloroquine after asking the White House doctor if he could take it -- despite the fact that he's said he is negative for Covid-19 and several recent studies show the drug is ineffective against the coronavirus and may even be harmful.
"A couple of weeks ago, I started taking it," Trump said. He later said he'd been taking it every day for a week and a half.
Asked if the White House doctor recommended that, Trump responded, "no."
"I asked him what do you think, he said, 'Well if you'd like it,'" the president told reporters.
There is no evidence that taking hydroxychloroquine could prevent infection with Covid-19.
A new study -- the largest of its kind -- shows that hydroxychloroquine does not work against Covid-19 and could cause heart problems, CNN's Elizabeth Cohen reported last week.
The study was published in the Journal of the American Medical Association. It follows a study published in the New England Journal of Medicine that also showed the drug doesn't fight the virus.
Even before these reports were published, the US Food and Drug Administration and the National Institutes of Health issued warnings about using the drugs for coronavirus patients.
Trump said he hadn't been exposed. He started taking the drug because he had heard from frontline responders who sent him letters saying they were taking it preventatively.
"Here's my evidence: I get a lot of positive calls about it," Trump said.
The president he said he doesn't know if it works, but claimed "if it doesn't, you're not going to get sick and die."
The US Food and Drug Administration has warned against the use of hydroxychloroquine and chloroquine to treat the novel coronavirus and said they should only be used in hospitals or clinical trials because they can kill or cause serious side effects. These include serious heart rhythm problems in Covid-19 patients treated with the drugs, especially when they are combined with the antibiotic azithromycin or other medications that can affect the heart.
CNN's chief medical correspondent Dr. Sanjay Gupta wrote in 2018 that Trump has a common form of heart disease, based on the results of his physical.
Hydroxychloroquine is used to treat or prevent malaria and to treat autoimmune conditions such as lupus and rheumatoid arthritis.
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