A drumbeat of anecdotal evidence and high-level praise for hydroxychloroquine in coronavirus patients has spurred the FDA to authorize it for emergency use. That means doctors can prescribe it to patients without other options—and in COVID-19, their only other options are clinical trials.

With the emergency authorization, the HHS has accepted 30 million donated doses from Novartis’ Sandoz unit. And with a similar nod for another form of the med—chloroquine phosphate—officials accepted 1 million tablets from Bayer. Mylan and Amneal have each pledged donations or increased production of the drugs.

Evidence for the drugs, now approved to treat malaria, lupus and rheumatoid arthritis, remains preliminary in COVID-19 patients. Critics warn against touting their use before proven effective.

Despite those concerns, President Donald Trump and others have backed the medicines as promising treatments as the pandemic worsens. With the authorization over the weekend, HHS said the drugs have shown activity in lab studies and anecdotal reports suggest they may offer some benefit to hospitalized patients.

While HHS and other investigators conduct scientific studies on the drugs, the emergency use authorization is intended to facilitate donations and boost supply while allowing access for patients who aren’t able to participate in a clinical trial. The emergency approval requires that doctors and patients have access to a fact sheet that outlines risks and interactions with other medications.

“We’ll continue working around the clock to get American patients access to therapeutics that may help them battle COVID-19, while building the evidence to evaluate which options are effective,” HHS Secretary Alex Azar said in a statement.

The emergency approval follows routine praise for the drugs from President Donald Trump and preliminary study results out of France. In an update last week detailing results for 80 hospitalized patients, professor Didier Raoult and his team said 93% of patients tested negative eight days into treatment with hydroxychloroquine and the antibiotic azithromycin.

"This allowed patients to rapidly be discharged from highly contagious wards with a mean length of stay of five days,” the team wrote. “Other teams should urgently evaluate this cost-effective therapeutic strategy, to both avoid the spread of the disease and treat patients as soon as possible before severe respiratory irreversible complications take hold.”

But there's been debate over Raoult's methodology among scientists. Influential chemist and blogger Derek Lowe wrote that even after the recent update, he's "less hopeful" about the drugs than before.

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Novartis CEO Vas Narasimhan sees some promise, but he acknowledged the data are preliminary. He told Swiss newspaper SonntagsZeitung that the company is “working with Swiss hospitals on possible treatment protocols for the clinical use of the drug, but it's too early to say anything definitively," Reuters reports. Further, Novartis is scouting for supplies to make more hydroxychloroquine, he added.

Aside from the hydroxychloroquine effort, HHS and others are looking at a range of existing medicines for possible treatment, plus urgently advancing new drugs and vaccines.