What is chloroquine?

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An Arizona man has died and his wife is in critical condition after they both took the drug chloroquine phosphate, which is an ingredient found in fish tank cleaner. The additive is also found in an anti-malaria medication which has been touted as a treatment for coronavirus despite a lack of study on it or approval by federal health agencies.

The couple, both in their 60s, required immediate hospital assistance within 30 minutes of ingesting the drug, which is normally used at aquariums to clean fish tanks, according to Banner Health, which is headquartered in Arizona.

“Given the uncertainty around COVID-19, we understand that people are trying to find new ways to prevent or treat this virus, but self-medicating is not the way to do so,” said Dr. Daniel Brooks, Banner Poison and Drug Information Center medical director. “The last thing that we want right now is to inundate our emergency departments with patients who believe they found a vague and risky solution that could potentially jeopardize their health.”

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The man couldn't be resuscitated when he arrived at a hospital, but his wife was able to throw up much of the chemical, Banner said.

What they consumed was reportedly not the malaria medication form of chloroquine, but an ingredient listed on a parasite treatment for fish, according to NBC News.

The man's wife told NBC News she watched televised briefings during which President Trump talked about the possible benefits of chloroquine to help the virus.

"I saw it sitting on the back shelf and thought, 'Hey, isn't that the stuff they're talking about on TV?'" she said, according to the broadcasting company. "We were afraid of getting sick."

So what is chloroquine?

Chloroquine, also known as chloroquine phosphate, is a drug normally used to prevent or treat malaria caused by mosquito bites in countries where the disease is most common. It usually comes as a tablet that you can take by mouth.

It's also described as "the saltwater aquarium wonder drug" and is the drug of choice for many public aquariums, including the Georgia Aquarium.

As for the coronavirus, chloroquine and a similar drug, hydroxychloroquine, have shown encouraging signs in small, early tests against the virus, but they have yet to be studied during a controlled clinical trial.

Both are oral prescription drugs that have been used for the treatment of malaria and certain inflammatory conditions since the 1940s. Chloroquine has been used for malaria treatment and chemoprophylaxis. Hydroxychloroquine is used for the treatment of rheumatoid arthritis, systemic lupus erythematosus, and porphyria cutanea tarda, according to the Centers for Disease Control and Prevention (CDC).

Doctors in South Korea, China, and France have reported the treatments to have positive results when administered to COVID-19 patients, according to the New York Times.

Christian Estrosi, the mayor of the French city of Nice, said on television Monday that he was on his sixth day of treatment with hydroxychloroquine and has "the sense I’ve been cured."

A Florida man with coronavirus had also previously claimed that hydroxychloroquine saved his life, according to the New York Post.

But scientists warn that beliefs on a possible cure have not come from large, carefully controlled studies that would provide the global medical community with actual proof that they work. Many doctors also don't want to raise false hope and back a drug that could still pose health risks to the worldwide community.

"There are no currently available data from Randomized Clinical Trials (RCTs) to inform clinical guidance on the use, dosing, or duration of hydroxychloroquine for prophylaxis or treatment of SARS-CoV-2 infection," the CDC added. "Although optimal dosing and duration of hydroxychloroquine for treatment of COVID-19 are unknown, some U.S. clinicians have reported anecdotally different hydroxychloroquine dosing."

One study starts on March 24 in New York.

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The drugs can also have major side effects, a reason doctors don't want to give them out without scientific evidence of their value, even during a global pandemic.

Chloroquine has been used to treat malaria since the 1930s. Hydroxychloroquine came along a decade later and has fewer side effects. The latter is sold in generic form and under the brand name Plaquenil for use against several diseases.

The drugs can cause heart rhythm problems, severely low blood pressure, as well as muscle or nerve damage.

"Chloroquine is an extremely toxic drug with a terrible side effect profile. Hydroxychloroquine is far safer, but its side effects are still significant," Meghan May, a microbiologist at the University of New England College of Osteopathic Medicine said. "If it is not abundantly clear that it is beneficial, giving this drug to a critically ill patient feels risky."

Banner Health advises checking with a primary care physician if you may be sick with COVID-19. They added that the use of specific treatments, including those labeled as 'anti-COVID-19' is not recommended for non-hospitalized patients -- like chloroquine.

Roughly 80 percent of people who become infected with COVID-19 only require symptomatic care and self-isolation to prevent the risk of infecting others, according to the WHO.

“We are strongly urging the medical community to not prescribe this medication to any non-hospitalized patients,” said Dr. Brooks.

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During a briefing on Mar. 20, Trump said that chloroquine and hydroxychloroquine if used together could help in treating the virus, the Times reported.

On Saturday, he tweeted that a combination of hydroxychloroquine and azithromycin -- a common anti-bacterial agent -- if used together could be effective.

"HYDROXYCHLOROQUINE & AZITHROMYCIN, taken together, have a real chance to be one of the biggest game-changers in the history of medicine," he Tweeted.

Anthony Fauci, the nation's top disease expert appointed to the White House Coronavirus Task Force said the therapy must be tested before its safety could be assumed.

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When asked if the drug was promising, Fauci said “the answer is no," describing it as "anecdotal evidence," according to ABC News.

The Associated Press contributed to this report