When Jacob Waters saw a study about the decades-old drug he takes for lupus being tried on the coronavirus, he started dialing the pharmacy.

“My assumption was, regardless of whether the study showed positive effects, there would be an increase in demand with the logic that people are desperate for solutions,” said Waters.

The 31-year-old South Philadelphia resident’s hunch was right.

After President Donald Trump started touting the drug, first used against malaria, as a treatment for COVID-19 on Twitter and in TV news conferences, new prescriptions for hydroxychloroquine and chloroquine, another version of the anti-malaria drug, began flooding into pharmacies. People who take the medication to treat chronic autoimmune conditions — a use approved by the U.S. Food and Drug Administration — are struggling to get their prescriptions filled, and leading medical associations are condemning inappropriate prescribing and stockpiling.

“We know — quite factually and evidence-based — that it does a lot of clear good for people with these autoimmune diseases, vs. a hypothetical benefit that is not evidence-based for people with COVID-19,” said Jules Lipoff, a physician and assistant professor of clinical dermatology at the University of Pennsylvania Perelman School of Medicine.

‘Not a miracle drug’

Chloroquine was introduced in the 1930s and became a powerful tool against malaria.

Today, hydroxychloroquine is most commonly used to treat lupus and rheumatoid arthritis, inflammatory conditions that can affect organ systems, joints, and skin, though effects vary among patients. Taken daily, the drug works as an anti-inflammatory, helping patients avoid painful flare-ups.

As scientists grapple for ways to control the coronavirus pandemic, hydroxychloroquine and chloroquine are among the approved drugs being considered as potential treatments, and have even been given to hospitalized COVID-19 patients in other countries with apparent success.

But because the drugs have been evaluated for this purpose only in small-scale studies, doctors warn that taking them without understanding the risks could be dangerous. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, who has stood beside Trump during his COVID-19 news conferences, cautioned that available evidence is “anecdotal” and that more research is needed.

The drug is among those being studied in clinical trials. Testing could show, for instance, that chloroquine may not work equally well among young and old individuals, or among those experiencing mild vs. severe symptoms, said Akhil Vaidya, director of Drexel University’s Center for Molecular Parasitology.

With no vaccine or cure for the coronavirus, public hope is high, but experts are cautious.

“It’s not going to be a miracle drug by any means,” Vaidya said. “It’s not going to be something that stops the virus in its tracks and kills it. It may have some effect. We just don’t know yet.”

For starters, consider that malaria is caused by a parasite. COVID-19 is a virus. Viruses are not “alive,” which means they cannot be killed.

Hydroxychloroquine could lessen the virus’ impact enough that the immune system is able to recover — but it will not eradicate the virus from the body, Vaidya said.

» READ MORE: Why the coronavirus and most other viruses have no cure

Here’s how dangerous self-dosing can be: An Arizona man died and his wife is in critical condition after they swallowed an aquarium cleaner containing chloroquine phosphate, which is similar to the prescription drug but not a substitute for it.

Vice President Mike Pence fanned the flames this week by announcing the federal government was authorizing the “off-label” use of hydroxychloroquine for COVID-19. The comment was meaningless — any drug approved for sale in the United States can be prescribed for “off-label” use, though insurance companies may not pay for it. Yet Pence validated the rush to buy up chloroquine, Vaidya said.

‘Grave consequences’

Off-label or not, the drug requires a prescription, leading some pharmacists to suspect the onslaught of sudden fill requests are from doctors seeking the medication for themselves, family, and friends.

Patricia Epple, CEO of the Pennsylvania Pharmacists Association, said that some pharmacies have already seen an increase, including one that reported filling 14 prescriptions for the drug from a single doctor — all apparently for the doctor and family members.

In a joint statement, the American Medical Association, the American Pharmacists Association, and the American Society of Health-System Pharmacists condemned inappropriate ordering and prescribing.

“Stockpiling these medications — or depleting supplies with excessive, anticipatory orders — can have grave consequences for patients with conditions such as lupus or rheumatoid arthritis if the drugs are not available in the community,” the organizations wrote.

The Pennsylvania Pharmacists Association has urged the commonwealth to restrict sales of the drug, as other states, including Ohio, Texas, Idaho, and Nevada, have done.

Pennsylvania Health Commissioner Rachel Levine said during a Thursday news conference that her department is working with pharmacists “to try to make sure that patients who are using these medications for accepted FDA uses have access,” but was not specific.

In the meantime, pharmacies could, for instance, require a COVID-19 diagnosis or evidence of a positive test result before filling a script, a tactic commonly used to limit opioid prescriptions, Epple said.

CVS Caremark said it would limit the amount of hydroxychloroquine and other drugs being evaluated for COVID-19 treatment, though limits will not apply to people who already take the medication for FDA-approved conditions.

Patients like Waters are hopeful those steps help. But he worries about people who run out of medication before they’re able to get a refill.

“I can empathize with people who are hungry for a solution in such scary and unprecedented times,” he said. “Maybe having a bottle of hydroxychloroquine might make you feel good and comfortable, but it’s endangering others.”

Sarah Anne Hughes of Spotlight PA contributed to this article.