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Nevada Gov. Steve Sisolak has restricted the prescription of two malaria medications that President Trump named as potential remedies for coronavirus, after a man died and his wife was hospitalized for using a fish tank cleaning additive with a similar name as a substitute.

Sisolak, a Democrat, issued an executive order Tuesday prohibiting prescriptions of chloroquine and hydroxychloroquine for coronavirus patients after the president mentioned the two drugs during a press briefing.

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"While the two drugs have necessary medical purposes, there is no conclusive evidence at this time among COVID-19 experts or Nevada's own medical health advisory team that the drugs provide treatment for COVID-19 patients," Sisolak said in a statement.

While addressing reporters, Trump mentioned both drugs as being fast-tracked for use as treatment, touting their likelihood of being effective despite the FDA still testing it for coronavirus use.

The order also limits a prescription to a 30-day supply to ensure it’s available for “legitimate medical purposes" and so that people cannot find a way to stockpile the drug.

Sisolak faced a backlash from Trump allies over the order, as the drugs are in fact being used in trials. They are among a select group of possible therapies the World Health Organization is currently looking at as potentially treating or preventing COVID-19, though the effectiveness of the drugs remains unclear.

The WHO originally did not have the two drugs as part of their trial, but high interest led them to reconsider.

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A French study showed that some patients had "a significant reduction of the viral carriage" after being treated with hydroxychloroquine, with better results when also given azithromycin. The U.S. Society of Critical Care Medicine, however, issued guidance saying that there "is insufficient evidence to issue a recommendation on the use of chloroquine or hydroxychloroquine in critically ill adults with COVID-19."

In Arizona, one man died and his wife landed in critical condition after the pair reportedly drank fish tank cleaner ingredient chloroquine phosphate, allegedly believing that they were ingesting the same anti-malarial medication currently being touted by officials as a possible COVID-19 treatment. There are major differences between the anti-malaria drug and the liquid the couple in Arizona allegedly ingested.

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“The production of medication is highly regulated -- both for purity and concentration,” Dr. Shannon Sovndal, a board-certified doctor in both emergency medicine and emergency medical services, told Fox News. “Over-the-counter products don’t follow the same guidelines. Dosing is critical, both for therapeutic effect and potentially dangerous side effects.”

Fox News' Alexandria Hein and The Associated Press contributed to this report.