April 7, 2020 -- The use of the anti-malarial drug chloroquine to treat COVID-19 patients has been halted at several Swedish hospitals due to reported side effects such as cramps and loss of peripheral vision.

Sahlgrenska University Hospital is one of those facilities. It stopped the use of chloroquine in the treatment of COVID-19 about two weeks ago.

"There were reports of suspected more serious side effects than we first thought," Magnus Gisslen, a professor and chief physician at Sahlgrenska University Hospital infection clinic, told the Gothenburg Post on April 1, Newsweek reported.

"We cannot rule out serious side effects, especially from the heart, and it is a hard-dosed drug. In addition, we have no strong evidence that chloroquine has an effect on COVID-19," Magnus Gisslen said.

No specific drugs are used to treat COVID-19 but some people have advocated the use of the anti-malarial drugs chloroquine and hydroxychloroquine.

U.S. President Donald Trump has touted the use of hydroxychloroquine in particular and announced Sunday that the federal government had stockpiled 29 million hydroxychloroquine pills for the treatment of COVID-19, Newsweek reported.

The use of hydroxychloroquine to treat COVID-19 was approved last month by the U.S. Food and Drug Administration, even though scientific studies of the two anti-malarial drugs have yielded mixed results.

For example, one study found they provide no additional benefit to COVID-19 patients who are already receiving antiviral drugs, Newsweek reported.