The unidentified man took 15 chloroquine pills, before exhibiting symptoms including vomiting, respiratory failure and hypotension. He was taken to a local hospital for emergency treatment, before being transferred to Bach Mai Hospital on March 7, said Nguyen Trung Nguyen, director of Bach Mai's toxic management department.

The man said he had heard rumors that chloroquine, a drug used to treat malaria, rheumatoid arthritis and lupus erythematosus, could prevent and cure Covid-19. He was recently discharged from hospital, said Nguyen.

Chloroquine cannot be prescribed without a doctor's recommendation, so people should not buy and use them themselves, stated the Health Ministry. Vietnam has not used chloroquine to treat Covid-19, neither has the ministry recommended the drug to prevent the disease, it added.

Rumors that chloroquine could be used to treat Covid-19 have surfaced after U.S. President Donald Trump on March 19 called on the U.S. Food and Drug Administration (FDA) to streamline the regulatory approval process for generic antimalarial drug hydroxychloroquine as a potential treatment for Covid-19, Reuters reported. FDA Commissioner Stephen Hahn at the time said his agency was working quickly to examine all possibilities.

Hydroxychloroquine is a less toxic derivative of chloroquine.

Following Trump's statement, demand for hydroxychloroquine surged, with the American Society of Health-System Pharmacists (ASHP), which maintains a list of drugs in shortage independent of the U.S. Food and Drug Administration’s list, adding the generic malaria drug to its basket on Thursday. Four out of eight manufacturers of the drug are currently in shortage, it said.

The HCMC Center for Disease Control warned people not to hoard chloroquine on Sunday, adding the drug carries a certain level of toxicity.

Le Quoc Hung, head of the department of tropical diseases at HCMC's Cho Ray Hospital, said: "Recently I heard people were rushing to buy hydroxychloroquine, causing a virtual shortage and making its price skyrocket, which is a surprise for us doctors."

Hydroxychloroquine can be mass-produced in Vietnam, so shortage should not be a problem, doctors said.

In Vietnam, a bottle of chloroquine, distributed under the brand name Cloroquin Phosphat and containing about 150-250 pills, typically sells for around VND100,000 ($4.3). But recent demand surges have increased the price 1.5-2 times.

The country has confirmed 116 Covid-19 cases so far, of whom 17 have been cured and discharged from hospital. Many of the currently active cases are Vietnamese nationals retuning from Europe and the U.S. as well as foreigners visiting from the same regions.

The Covid-19 pandemic has so far infected over 330,000 people globally, claiming nearly 14,700 lives.