Now its derivative, hydroxychloroquine, is also used to treat lupus and rheumatoid arthritis.
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Millions of Americans use it to treat those two diseases including Erin White, of Raleigh, who has lupus.
Because of his lupus, White is very worried about contracting COVID-19.
"As someone with an immune disorder, I am at higher risk for severe complications from coronavirus," he told ABC11 via Skype from his home where he is practicing social distancing.
Right now, the main drug being talked about as a possible treatment for the coronavirus is hydroxychloroquine, the same drug White takes for his lupus.
As someone hoping for a treatment for COVID-19 and as a lupus patient who takes hydroxychloroquine, that talk from the President of the United States on down leaves him with mixed emotions.
"If in fact, hydrochloroquine is an effective treatment for coronavirus, that'll be fantastic. That'll be great. There are a lot of people that need some treatment for it right now," he said, " I just don't know what it will mean for all the people who take hydrochloroquine for other reasons."
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White isn't the only one concerned.
The day after President Trump first mentioned it publicly, White got a call from his doctor at Duke Health.
Fact Check: Pres. Trump pitches drug unapproved for coronavirus
"It was important enough for my doctor to make sure I got a 3-month supply in hand as soon as all this news started coming out."
His pharmacist, Maresa Roney at Person Street Pharmacy, wasn't surprised when his refill request came in.
"We've seen it on the FDA that a shortage is coming. I saw it on the news last night that it looks like India, who's a main supplier of drugs, isn't going to ship it to the United States," she said.
That is until President Trump threatened retaliation.
LA doctor seeing success with hydroxychloroquine to treat COVID-19
ABC News now reports that India, which currently supplies nearly half of America's hydroxychloroquine, is now saying it won't completely shut down that pipeline.
And apparently there is also an effort to increase production around the world.
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But that still doesn't clarify things for White.
Trump says FDA to approve existing drugs for coronavirus treatment
"Between my doctor and my pharmacy, I'm in good shape right now. We obviously don't know what the future brings," he said.
If hydroxychloroquine does turn out to be the COVID-19 treatment we're all anxiously awaiting, those who use it for other reasons can only hope manufacturing of the drug catches up quickly.