[Blog] Hydroxychloroquine and chloroquine for prevention of COVID-19

What is the issue?

So far, there are over 5 million confirmed cases of COVID-19 worldwide with nearly 340,000 deaths. To date, there has been no proven medication or vaccine to prevent or treat COVID19, however there are some early stage research studies ongoing with regards to vaccine development. In the meantime, there may be a risk of significant impact on healthcare systems where the number of patients affected by COVID-19 overwhelms the healthcare system capacity. Many countries are therefore looking at using older drugs to see if they help against COVID-19.

There is therefore a trial (COPCOV) to use two drugs, hydroxychloroquine and chloroquine to try and slow the replication of the virus in people exposed to the virus. This may prevent the spread of the infection.

The COPCOV trial is an international study where participants will be randomised to either hydroxychloroquine or placebo (in Europe and Africa) and chloroquine or placebo (in Asia). They will be taking these drugs for 3 months and then be monitored thereafter for the development of COVID-19. The plan is to recruit 40,000 participants overall. It will not be open to the general public but rather will be focused on adult workers working in healthcare facilities who are delivering care to patients with confirmed or suspected COVID-19. The aim of the study is to see whether people who take hydroxychloroquine or chloroquine are at a lower risk of contracting COVID-19.

What is hydroxychloroquine? What is chloroquine?

Chloroquine is an anti-malarial drug which was discovered in the 1930s and has been primarily been used to prevent malaria. It is cheap and is easily administered. It has also been used for other conditions such as rheumatoid arthritis, systemic and discoid lupus erythematosus and psoriatic arthritis.

Hydroxychloroquine was synthesised in the 1940s and has become more popular as a treatment for auto-immune diseases. It appears to have slightly fewer side effects compared to chloroquine. Hydroxychloroquine has also been used for treatment and prevention of malaria, rheumatoid arthritis and lupus erythematosus.

So far, no studies have tested the use of hydroxychloroquine or chloroquine for prevention of COVID-19 in humans. There have been some laboratory studies which have shown that these drugs have some antiviral activity against COVID-19 in laboratory studies but it is not known whether the same benefits will be seen in humans.

What are the side effects?

Overall, these medications are generally well tolerated and are safe when administered with the appropriate monitoring. It is generally thought that the side effects of these drugs become a problem when the drugs are administered at high doses for a long time. The doses used in these trials will not be higher than doses currently used for treating medical conditions such as rheumatoid arthritis.

The serious side effects of chloroquine are: dangerous heart rhythm problems, heart failure, liver function disturbance, anaemia, hypoglycaemia, seizures and effects on the retina. Similar side effects are also seen with hydroxychloroquine.

Monitoring is therefore required with blood tests (check for anaemia, liver function, renal function), ECG monitoring, eye examination and regular clinical check-ups.

Aside from the direct side effects of the drugs, there is also concern regarding the consequences for other conditions if the drugs start to be used for COVID-19. There is concern that patients with long term conditions such as rheumatoid arthritis or lupus will not be able to have adequate supply of hydroxychloroquine and chloroquine and therefore their condition may deteriorate. This needs to be a factor should be kept into consideration.


In a climate where we do not have any convincing medications or vaccines to prevent and treat the COVID-19, this trial is a great way to test old therapies against a new enemy. Although these drugs are generally safe, there is a risk of serious side effects if the patients are not adequately monitored. We will await the results of this trial and hope that it gives some positive news!

By Dr Yanish Purmah from UK

Mots clés

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