The cheap steroid touted as a 'breakthrough' coronavirus drug may carry a small risk for people who don't need respiratory support

• On June 16, the authors of a major clinical trial of dexamethasone said the steroid reduced deaths by one-third for COVID-19 patients on ventilators. The UK's National Health Service (NHS) gave the drug immediate approval.
• The drug is used to tamp down immune system reactions, which can be helpful in late stages of the disease when the immune system has gone into overdrive.
• The full results of the trial have only just been released, 9 days later, and in it there is a mention of possible harm to people with milder cases.
• The risk for harm was not statistically significant, the study said, but some researchers say it makes sense because the drug can hamper the body's immune system reactions during a time when they are most needed.

Last week, the British scientists behind a major clinical trial on dexamethasone announced the cheap steroid reduced deaths by one-third for COVID-19 patients on ventilators. That day, June 16, the British government gave dexamethasone immediate approval to be used as a treatment for the disease caused by the novel coronavirus.

Nine days later, the team finally released the results of their highly-anticipated study for others to review, and buried among the promising data is a mention of the possible harm dexamethasone could cause to people with milder cases of the disease.

The report, which has not yet been peer-reviewed or officially published, found that, though the steroid is a boon to critically ill patients, timing is critical, and giving the drug too early could, in rare cases, have adverse effects.

Of the 6,400 patients included in the study, those with mild cases who took dexamethasone died at a slightly higher rate than other patients with mild cases who didn't take the drug.

Crucially, the risk for harm was statistically insignificant. But experts say it makes sense: dexmethasone functions by tamping down immune system responses. For people with mild cases, taking the drug may be hampering their immune system during the time immune system functions are most needed to fight off disease.

Dr. Samuel Brown, an assistant professor of pulmonary and critical care medicine at University of Utah School of Medicine, told the New York Times that the drug "may harm some patients, and we're not entirely sure which patients those are."

Dexamethasone is used in cancer patient to tamp down the immune system during treatments

Dexamethasone is a steroid that was first approved in the US in 1958. The cheap, generic medication has become widely used in cancer patients for a variety of roles. In some blood cancers, dexamethasone can have a cell-killing effect. Other times, it is used to prevent nausea.

COVID-19 researchers eyed the steroid for a different reason: its effect on the immune system. New cancer therapies called immunotherapies often use a patient's own immune system to fight the tumor. But a common side effect is these treatments can trigger an immune response. Dexamethasone is used to tamp down that immune reaction.

The drug seems to help prevent the immune system from overreacting in COVID-19 patients

The UK researchers wondered if it may be able to do the same in critically ill COVID-19 patients. In the late stages of the disease, the body's immune response can go into overdrive, often causing more damage than the virus.

That theory was further supported by clinical results published in February in The Lancet. A study of 277 patients with acute respiratory distress syndrome showed dexamethasone led to more ventilator-free days and fewer deaths.

"It seems biologically plausible that you can extend that benefit to patients who have this new cause of the same syndrome," Dr. Taison Bell, an infectious disease and critical care physician at the University of Virginia, told Business Insider.

Why dexamethasone is probably pointless for people with mild cases, and could even be harmful

Dexamethasone does not appear to help mild cases because in the early stages of having a disease, your immune system is crucial for fighting it off. Dexamethasone can suppress the immune system from reacting properly and fighting off the disease.

Dr. Nina Shah, a blood cancer physician and associate professor of medicine at UCSF Health, who commonly uses dexamethasone to treat cancer patients, says it makes sense that dexamethasone could have an adverse effect on people with mild cases of COVID-19.

"The most concerning thing about using any steroid is its anti-inflammatory activity, which is exactly why they're using it here," she told Business Insider. "And so there's a chance it could potentially impair the immune system from doing its job. So here you really have to thread the needle of having too much immune system activity and too little activity."

She noted that the dose used in this trial, of 6 milligrams daily for 10 days, is much lower than typical doses used in cancer treatment settings. "Based on my experience treating people with 40 milligrams in one day, I don't think 6 milligrams is such a huge dose to worry about as far as side effects," she said.

She did note that possible side effects included higher blood sugar, agitation, and that risk of suppressing the immune system.