A drug used to treat malaria for decades is being tested to see if it works for coronavirus, after reports that it helped patients in China.

Chloroquine and a closely linked drug, hydroxychloroquine, have been shown to inhibit the coronavirus in laboratory tests. Unpublished clinical studies from China have reportedly found the drug effective.

The drug gained prominence at a White House press conference where it was announced that chloroquine had been approved for use in COVID-19 patients by the US Food and Drug Administration. That was not entirely correct. People in Nigeria have reportedly been panic-buying the drug.

The World Health Organisation is organising multinational trials of hydroxychloroquine and three other drugs or combinations. On March 8, 23 trials of hydroxychloroquine had been registered.

Doctors can use treatments for conditions other than those that have been officially approved, a prescribing practice known as “off-label”. But it is also seems wise to gather better evidence to see if chloroquine is safe and effective for treating COVID-19 in larger trials compared to other medication.


Where did the story come from?

There have been widespread reports in the media and social media about chloroquine being effective against coronavirus. It makes sense to trial existing drugs, which have been used for other conditions, when looking for ways to treat new viruses.


What is the basis for the claim?

Doctors and researchers looking for responses to new infectious agents start with existing drugs known to affect similar agents. In this case, drugs used against previous coronaviruses (such as those that caused SARS and MERS) and known to have anti-viral action, were investigated.

Interest in chloroquine emerged in February, when a letter published in the journal Cell Research reported that chloroquine was highly effective against coronavirus in laboratory tests. Laboratory testing does not involve people or animals but looks to see whether introducing the drug to a culture of the virus inhibits its growth. The study also found remdesivir, a drug developed to combat Ebola, was highly effective.

Also in February, a letter published in BioScience Trends said Chinese trials on “more than 100 patients” had found chloroquine prevented pneumonia from worsening and speeded clearance of the virus. As these trials have not been published and their findings shared we don’t know if they were high quality.

Because of interest prompted by the Chinese reports, the WHO decided to include chloroquine in its multi-national trial. The drug will also be tested in a European trial announced this week.

An analysis of registered trials of coronavirus research by the UK Centre for Evidence Based Medicine found that 382 studies had been registered by March 8, 23 of them to test chloroquine. These researchers said that the studies from China so far were characterised by poor quality and small sample size.


What do trusted sources say?

The World Health Organisation’s guidance on management of COVID-19 says that there is no current evidence to recommend any specific anti-COVID-19 treatment for patients with confirmed COVID-19. It recommends investigational anti-COVID-19 therapeutics are used in ethically approved, randomised, controlled trials.

The US Center for Disease Control also states that there are currently no antiviral drugs licensed by the U.S. Food and Drug Administration to treat patients with COVID-19. It adds, that there are no currently available data from randomized clinical trials to inform clinical guidance on the use, dosing, or duration of hydroxychloroquine for prophylaxis or treatment of SARS-CoV-2 infection.

Analysis by EIU Healthcare, supported by Reckitt Benckiser



1.     Jianjun G et al. Breakthrough: Chloroquine phosphate has shown apparent efficacy in treatment of COVID-19 associated pneumonia in clinical studies. BioScience Trends 14, 1; 2020. https://www.jstage.jst.go.jp/article/bst/14/1/14_2020.01047/_article (Accessed 25 March 2020)

Reading list

1.     Wang, M et al. Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro. Cell Res 30, 269–271 (2020). https://doi.org/10.1038/s41422-020-0282-0 (Accessed 25 March 2020)

2.     Aronson J et al. COVID-19 trials registered up to 8 March 2020—an analysis of 382 studies. Centre for Evidence Based Medicine, Oxford University. https://www.cebm.net/oxford-covid-19/covid-19-registered-trials-and-analysis/ (Accessed 25 March 2020)

3.     World Health Organisation. Clinical management of severe acute respiratory infection when novel coronavirus (nCoV) infection is suspected. https://www.who.int/publications-detail/clinical-management-of-severe-acute-respiratory-infection-when-novel-coronavirus-(ncov)-infection-is-suspected (Accessed 25 March 2020)