An Arizona man has died and his wife is in a critical condition after both ingested a form of chloroquine in an apparent effort to guard against Covid-19.
The drug has been touted by President Donald Trump as a possible treatment for the virus.
It is also an additive commonly used to clean fish tanks.
Shortly after ingestion, the couple fell ill, said Arizona-based hospital system Banner Health.
The couple were both in their 60s.
The woman told NBC News she had seen a televised briefing in which Mr Trump discussed the potential benefits of chloroquine as a treatment Covid-19.
The drug has been approved by the US Food and Drug Administration (FDA) for treating malaria, lupus and rheumatoid arthritis but is unproven for use against the novel coronavirus.
“We saw his press conference. It was on a lot, actually,” she said. “Trump kept saying it was basically pretty much a cure.”
“We were afraid of getting sick,” she told NBC.
There are at least 46,548 confirmed cases of the virus throughout the US, with at least 592 deaths.
The couple had used chloroquine previously as a treatment for their koi fish and still had some remaining in their home. This additive is formulated differently than the drug used to treat malaria.