Dexamethasone

This article was last reviewed on 14 December 2021.

Dexamethasone was the first medicine shown to reduce deaths from covid-19. It belongs to a class of drugs called steroids, which damp down the immune system. Our immune response is normally what saves us from attack by viruses and bacteria, but in people with severe covid-19, it seems to overreact. Immune cells congregate in the lungs, releasing high levels of immune signalling chemicals called cytokines, which attract yet more immune cells, in a vicious circle known as a cytokine storm. This leads to excessive inflammation in the lungs, with fluid leaking into the air spaces, hindering intake of oxygen.

Steroid drugs like dexamethasone are often used to treat other diseases caused by an overreactive immune system, like allergies, and have also been used previously to treat people in intensive care with lung inflammation. But steroids reduce the immune system’s ability to fight bacteria, so it was unclear if they would be beneficial overall in covid-19, where there is a risk that patients develop secondary bacterial infections.

The answer came in 2020 from a large randomised trial of giving dexamethasone or placebo to people with severe covid-19 in the UK. In people who were on ventilators, 41 per cent of those who got the placebo died, while 29 per cent of those who got the steroid died. This is a relatively large effect, compared with drug treatments for other diseases. There was also a smaller survival advantage in people who were less severely ill and needed supplementary oxygen but weren’t on a ventilator.

People outside of hospital should not start taking dexamethasone or other steroids on their own initiative, though, because the negative effects on the immune system might outweigh any benefits. In fact, the UK trial found dexamethasone gave no survival benefit for hospital patients with covid-19 who were not sick enough to need extra oxygen.