paper published in The Lancet has cast fresh controversy on the use of the malaria drug hydroxychloroquine as a potential treatment for COVID-19.

The study’s authors reported they were “unable to confirm a benefit” of using the drug, while also finding COVID-19 patients in hospital treated with hydroxychloroquine were more likely to die or suffer life-threatening heart rhythm complications.

The publication prompted the World Health Organisation to suspend its testing of hydroxychloroquine to treat COVID-19, while a similar Australian trial has paused recruitment.

Hydroxychloroquine has been used since the 1940s to treat malaria, but has been making headlines as a potential treatment for COVID-19. US President Donald Trump recently declared he was taking it daily.

The drug alters the human immune system (it’s an immunomodulator, not an immunosuppressant) and has an important role in helping people with rheumatoid arthritis and lupus.

It does have a range of serious possible side-effects, including eye damage and altered heart rhythm, which require monitoring.

What did the study find about hydroxychloroquine?

Treatment with hydroxychloroquine was associated with increased rates of death in people with COVID-19, even after the researchers adjusted for other factors (age, other health conditions, suppressed immune system, smoking, and severity of the COVID-19 infection) that might increase the risk of death.

About 18% of people who received hydroxychloroquine died in hospital, compared with 9% of people with COVID-19 who did not receive these treatments. The risk of death was even higher (24%) in people receiving hydroxchloroquine in combination with either of the antibiotics azithromycin or clarithromycin.

Hydroxchloroquine (6%) and chloroquine (4%) treatment was also associated with more cases of dangerous heart rhythm problems when compared with untreated people with COVID-19 (0.3%).

Any evidence of benefit, while not the focus of this study, was unclear.