SINGAPORE - From the use of ivermectin to credible-sounding organisations, websites such as Truth Warriors cite a variety of sources including studies and organisations helmed by doctors and physicians.

However, as The Straits Times has learnt, these sources and their claims are shrouded in controversy.

One such claim that has gained tremendous international attention is the drug ivermectin, a medication used to treat parasitic infections. Proponents of the drug have claimed that it is effective in treating or preventing Covid-19.

Ivermectin was created in the 1970s to treat parasites in livestock, but the drug gained new life as doctors looked at repurposing a plethora of existing drugs to see what might be effective against Covid-19.

Advocacy groups and online communities have formed around the world, such as the Front-Line Covid-19 Critical Care Alliance, which Truth Warriors cites as a source of credible information.

The alliance began as a non-profit network of doctors trying to establish Covid-19 protocols in the early days of the pandemic, but has come under scrutiny for its affiliation with prominent anti-vaccine organisations.

For instance, the United States Centres for Disease Control and Prevention and the Food and Drug Administration (FDA) have put out advisories warning against using ivermectin as treatment or prevention for Covid-19.

Currently available data does not show its effectiveness and taking large doses of ivermectin is also dangerous, the FDA warned.

Associate Professor Jenny Low, a senior consultant of infectious diseases from the Singapore General Hospital, said much of the controversy over ivermectin stems from the fact that its proponents have ignored the varying quality of trials testing this drug for Covid-19.

She said: "If we remove the 'noise' of poor quality clinical trials and their reports, and just focus on the ones that are of at least decent quality, then the current evidence does not support the use of ivermectin. That's not to say that the drug definitely does not work.

"We can only say that with the best evidence out there till date, there is no strong evidence to support its use."

Studies involving ivermectin have also proven to be problematic.

In July, a pre-print study on the efficacy and safety of ivermectin led by Dr Ahmed Elgazzar from Benha University in Egypt was retracted after serious ethical concerns were raised.

It claimed to be a randomised control trial but questions surrounding the credibility of the data surfaced.

In September, Buzzfeed News reported on an influential study from Argentina claiming ivermectin prevented Covid-19 all the time.

But its data remained questionable and it was reported that there were signs that at least some of the experiments did not happen as claimed.

Prof Low also noted that even the drug's manufacturer, Merck, has advised against the use of ivermectin for Covid-19.

Pre-clinical doses that showed the drug to work in the laboratory also cannot be used in humans as it is several hundred times higher than the doses recommended for humans, she added.

Some of the doctors cited by websites like Truth Warriors, such as Dr Joseph Mercola, have been identified as some of the most influential spreaders of Covid-19 misinformation online.

An osteopathic physician, Dr Mercola has long been a subject of criticism and government regulatory actions for his promotion of unproven or unapproved treatments.

In a warning letter from the FDA in February, the agency drew attention to various unapproved and misbranded products related to Covid-19 on Dr Mercola's website and social media sites.

He has become the chief spreader of coronavirus misinformation online, according to researchers, The New York Times reported in an updated article on Oct 6.

The Truth Warriors also cited immunologist Byram Bridle's claim that spike proteins created in response to mRNA vaccines are harmful to the body.

Dr Bridle also speculated that Covid-19 shots could lead to cardiovascular problems and infertility.

However, there is currently no such evidence to suggest that his claims are true.