Chloroquine is a synthetic form of quinine, which has been used to treat malaria since the 1940s.

The drug has recently been used to treat coronavirus patients in China and in France, where some researchers said it showed great promise, though scientists agree that only more trials would determine if it really works and is safe.

The US is fast-tracking the anti-malarial drug for use as a treatment against the new virus, US President Donald Trump said on Thursday.

"We're going to be able to make that drug available almost immediately, and that's where the FDA (Food and Drug Administration) has been so great," Trump told reporters.

"They've gone through the approval process — it's been approved. They took it down from many, many months to immediate. So we're going to be able to make that drug available by prescription."

But the FDA Commissioner Stephen Hahn later indicated that, while the drug has not yet been formally approved, access to it was being expanded so that authorities could gather more data.

This is known as "compassionate use".

"If there is an experimental drug that is potentially available, a doctor could ask for that drug to be used in a patient. We have criteria for that and very speedy approval for that," said Hahn.

"As an example, many Americans have read studies and heard media reports about this drug chloroquine, which is an anti-malarial drug.

"It's already approved, as the president said, for the treatment of malaria as well as an arthritis condition.

"That's a drug that the president directed us to take a closer look at, as to whether an expanded use approach to that could be done to actually see if that benefits patients."

Already in shortage, pharmacists say

The old malaria treatment, however, is in short supply as demand surges amid the fast-spreading outbreak.

The American Society of Health-System Pharmacists (ASHP), which maintains a list of drugs in shortage independent of the US Food and Drug Administration’s list, added the generic malaria drug chloroquine, or hydroxychloroquine, to its list on Thursday. Four out of eight manufacturers of the drug are currently in shortage, it said.

There are currently no vaccines or treatments approved for the disease, but researchers are studying existing treatments and working on experimental ones. At the moment, most patients can only receive supportive care.

Read: Coronavirus: How long before we have a vaccine?

Erin Fox, senior director of drug information at University of Utah Health, who maintains ASHP’s shortages list, said pharmacists are unable to get the drug or fill prescriptions in full.

Fox said that University of Utah’s 12 retail pharmacies are not filling prescriptions for prophylactic use, and are preserving their stocks for inpatient needs.

The FDA could not be reached for comment, but chloroquine is not currently on its drugs in shortage list.

Run on pharmacies

Fox and the FDA have been watching for drug shortages that could be due to supply chain issues with manufacturing in China and India. But surging demand in recent weeks is the issue with the malaria drug, which can also treat rheumatoid arthritis and lupus, according to online pharmacy, Honeybee Health.

Its co-Chief Executive Jessica Nouhavandi sent a letter to prescribers earlier this week, urging them to be aware of potential hoarding of the drug that could deprives those who really need it.

On Thursday, Nouhavandi said demand was its highest yet after Trump’s comments.

Jeff Bartone, who owns Hock’s Pharmacy in Vandalia, Ohio, said he purchased five bottles of hydroxychloroquine this morning, but within an hour the company that distributes it to his pharmacy had run out.

He said four backup prescription drug wholesalers were out of the drug as well.

Bartone said he does not typically stock large amounts of the drug because it is not widely prescribed.

Mylan NV, one of the manufacturers ASHP said was in shortage, said it was ramping up production of the drug and expects to be in a position to begin supplying it more broadly in mid-April.

It said with the raw materials on hand it can make 50 million tablets to potentially treat more than 1.5 million patients.

Bayer AG said it would donate 3 million tablets of Resochin, a closely related drug known generically as chloroquine phosphate. Chloroquine is also in shortage, according to the ASHP.

Online pharmacy Valisure said it too was unable to order any chloroquine or hydroxychloroquine as of Thursday from its four distributors.

Valisure Chief Executive David Light said other potential treatments are also becoming difficult to obtain.

“Kaletra and losartan are being rationed, meaning we are only allowed to order limited quantities at a time,” he said.

Kaletra, a combination HIV treatment and the generic blood pressure drug losartan, have been considered as potential treatments for the virus, although Chinese investigators reported this week that Kaletra failed to improve outcomes for seriously ill COVID-19 patients.