(CNN)The prospect of using hydroxychloroquine to treat Covid-19 amid the novel coronavirus pandemic has sparked rancor and disagreement among politicians and scientists.
There have been indications that the drug is effective in treating or preventing Covid-19, but the tests haven't endured the due diligence of extensive clinical trials.
What is its origin?
Can it be used to treat Covid-19?
It's unclear. In labs it has demonstrated some efficacy against the severe acute respiratory syndrome coronavirus responsible for the present pandemic. But the White House's coronavirus response coordinator, Dr. Deborah Birx, has said that efficacy in test tubes doesn't mean it will work in humans.
So it's an anti-malarial?
Yes, but since 2006, it has not been recommended for use in severe malaria because of problems with resistance, particularly in the Oceania region, according to the World Health Organization.
It also has value as a "disease-modifying anti-rheumatic drug" that can decrease the pain and swelling of arthritis, according to the American College of Rheumatology. It is used to treat rheumatoid arthritis, childhood arthritis, some symptoms of lupus and other autoimmune diseases.
"It is not clear why hydroxychloroquine is effective at treating autoimmune diseases. It is believed that hydroxychloroquine interferes with the communication of cells in the immune system," the college says.
Are more studies on humans coming?
Yes, lots of them. Drug maker Bayer has provided millions of doses to the federal government. And the US Food and Drug Administration, which has not officially approved hydroxychloroquine for treating Covid-19, issued an emergency use authorization to treat Covid-19 patients with it.
Also, in Detroit, 3,000 patients at Henry Ford Hospital will be part of a trial whose results will be tracked in a formal study, said Vice President Mike Pence, who is heading the White House's coronavirus response. The federal government is also working to get millions of doses into areas with high infection rates, another White House official said.
Why does Trump keep mentioning it?
The US Department of Health and Human Services has also cited the encouraging anecdotal reports, but it, too, insisted more clinical trials are needed.
But it's safe?
Trump points to the fact it's been in use for decades, "so we know that if things don't go as planned, it's not going to kill anybody."
Hydroxychloroquine is well tolerated in Covid-19 patients, the US Centers for Disease Control and Prevention says, while the American College of Rheumatologists says it's well tolerated in general.
Side effects are rare, the college says, and most commonly include nausea and diarrhea. Less common side effects include rashes, hair changes, weakness and, in rare instances, anemia or changes in vision.
That said, Nigerian officials have reported cases of overdoses, and an Arizona man who took a version of chloroquine designated for cleaning fish tanks died.
Should people just take it and see what happens?
Lupus patients routinely use the drug to treat their symptoms -- for some, there is no alternative. And it's the only known therapy for primary Sjögren's syndrome, another autoimmune disorder, The Lancet said.
Because of shortages spurred by coronavirus-related interest, the Lupus Foundation of America has called on drug makers to increase their production of hydroxychloroquine, and Kaiser Permanente is no longer filling routine prescriptions for chloroquine, The Lancet reported.
FDA Commissioner Stephen Hahn, who has called for a "large, pragmatic clinic trial" of the drug, has also urged caution, warning against "treating patients with a product that might not work when they could have pursued other, more appropriate treatments."