Narinder Nanu/AFP via Getty Images
This article was last reviewed on 15 Ocober 2021.
Hydroxychloroquine is a drug developed in the 1940s to treat malaria. It was hoped it could help treat coronavirus infections but several trials have shown it has no beneficial effects and might be harmful.
Hydroxychloroquine is a less toxic variant of another malaria drug called chloroquine, but hydroxychloroquine can still cause serious side effects, including heart problems and permanent damage to vision.
In most parts of the world, the malaria parasite has evolved resistance to both of these drugs, but hydroxychloroquine is now widely used for other purposes, such as treating the autoimmune disorders lupus and rheumatoid arthritis.
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Hydroxychloroquine has complex effects on the body. How it works against malaria and how it helps treat diseases such as lupus is still not well understood.
Some studies have suggested that both chloroquine and hydroxychloroquine have antiviral effects. For instance, in experiments in cells grown in dishes, chloroquine inhibits dengue virus. However, when the drug was given to people with dengue in a trial in Vietnam, no benefits were seen.
In February 2020, experiments in cells showed that chloroquine and hydroxychloroquine can inhibit the coronavirus. That led to both drugs being tested to see if they can treat covid-19.
Some small early studies suggested hydroxychloroquine did reduce the risk of dying from covid-19. As a result, several countries including China and the US authorised the use of hydroxychloroquine for treating people with severe coronavirus infections.
However, in June 2020 the results of a large randomised trial in the UK showed conclusively that hydroxychloroquine has no benefit when given to people hospitalised with covid-19. On the contrary, those given hydroxychloroquine stayed in hospital longer and those who were not on ventilators when given the drug were more likely to die.
Several other trials of hydroxychloroquine, either alone or in combination in with other drugs, have found no benefits for either hospitalised or non-hospitalised patients. Some, but not all of these studies, found evidence of harm.
As a result, the drug is not recommended for the treatment of covid.
