Dexamethasone
Of all the drugs being given to President Trump, dexamethasone is by far the most ominous: it is usually reserved for people who are seriously ill.
A cheap, widely used steroid, it is the only drug proven to save the lives of Covid-19 patients. It is thought to work by calming the immune system, which goes into overdrive in some people and turns on their own vital organs.
The Recovery trial, which involved thousands of NHS patients, showed that for people on ventilators it reduced the risk of death. For patients on oxygen, it reduced the risk that they would die and that they would need invasive ventilation, in which a tube is placed into the airway and oxygen forced in.
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