A limited emergency-use authorisation for two anti-malarial drugs touted as game-changers by President Donald Trump has been issued by the US Food and Drug Administration (FDA) to treat coronavirus patients.

In a statement published on Sunday, the US Department of Health and Human Services detailed recent donations of medicine to a national stockpile – including chloroquine and hydroxychloroquine, both being investigated as potential Covid-19 treatments.

It said the FDA had allowed them “to be distributed and prescribed by doctors to hospitalised teen and adult patients with Covid-19, as appropriate, when a clinical trial is not available or feasible”.

Trump said last week that the two drugs could be a “gift from God”, despite scientists warning against the dangers of overhyping unproven treatments.

Many researchers including Anthony Fauci, the US’ leading infectious disease expert, have urged the public to remain cautious until larger clinical trials validate smaller studies.

Two US medical bodies – the National Institutes of Health and the Biomedical Advanced Research and Development Authority – are currently working to plan such trials.

Some in the scientific community fear Trump’s endorsement of the medicines could create shortages for patients who need them to treat lupus and rheumatoid arthritis, diseases for which they are approved.

A man died in the US state of Arizona from taking a form of chloroquine after he took a form of the drug his wife had used to treat her pet fish.

The woman told NBC News: “I saw it sitting on the back shelf and thought, ‘Hey, isn’t that the stuff they’re talking about on TV?’”

Banner Health, a non-profit health care provider based in Phoenix, said on its website that “a man has died and his wife is under critical care after the couple, both in their 60s, ingested chloroquine phosphate, an additive commonly used at aquariums to clean fish tanks”.

The US has more than 140,000 novel coronavirus cases and 2,489 deaths, according to a tracker maintained by Johns Hopkins University.