Dexamethasone is a corticosteroid and is included in standard of care.

https://www.canada.ca/en/public-health/corporate/mandate/about-agency/external-advisory-bodies/list/covid-19-clinical-pharmacology-task-group/statement-dexamethasone.html

"Recommendations

The Clinical Pharmacology Task Group recommends that among hospitalized patients with COVID-19 who require supplemental oxygen or mechanical ventilation, dexamethasone 6 mg IV for 10 days (or until discharge, if earlier) or equivalent glucocorticoid dose should be strongly considered. This guidance is not meant to replace clinical judgment or specialist consultation.

This guidance will be updated as peer-reviewed evidence emerges, particularly regarding risks and benefits in older age groups, for those with different clinical presentations, and for different demographic subgroups such as sex and age.

This statement was approved by the Clinical Pharmacology Task Group on July 12, 2020."

Clinical evidence of efficacy to date

On June 22, 2020, Horby et al. released a preliminary report of clinical findings from the dexamethasone treatment arm of the RECOVERY trial on a pre-print website without peer review, one arm of many investigational treatment arms from the RECOVERY trial, a large randomized controlled multi-centre trial conducted at 176 NHS hospitals in the UK (n=2,104 randomized to dexamethasone; n=4,321 patients randomized to receive standard of care)Footnote12.

• Inclusion criteria: Hospitalized patients with confirmed or clinically suspected COVID-19 (no specified disease severity, age, or other demographic/clinical factor; age was restricted to over 18 years of age until May 9, 2020 when a protocol modification removed the restriction). Pregnant and breastfeeding women were eligible.
• Baseline characteristics: The majority of patients were male (64%); mean age 66.1 years.
• Intervention: Treatment was standard of care plus low-dose dexamethasone (6mg once daily by oral or i.v. administration up to 10 days) or standard of care alone.
• Primary Outcome: The authors reported a significant reduction in the primary outcome of 28-day mortality for patients on 6 mg daily treatment of dexamethasone (454/2104 (21.6%) compared to those receiving standard of care alone (1065/4321; 24.5%; RR 0.83 (0.74-0.92); p<0.001) with available data (4.8% of patients had not completed 28 day follow-up).
• Secondary outcomes (not adjusted for multiplicity):
  • Significantly more patients in the dexamethasone group were discharged from hospital by day 28 (1360/2104 (64.6%)) than those treated with standard of care alone (2639/4321 (61.1%); RR 1.11 (1.04-1.19); p=0.002).
  •  For those patients not receiving invasive mechanical ventilation at time of randomization, patients randomized to the dexamethasone treatment arm had significantly less risk of requiring invasive mechanical ventilation or death (425/1780; 23.9%) vs. those receiving standard of care alone (939/3638 [25.8%]; RR 0.91 [0.82-1.00]) or invasive mechanical ventilation alone (921/1780 [5.2%] - dexamethasone arm, compared to 258/3638 [7.1%] -  standard of care arm; RR 0.76 [0.61-0.96]).
• The following subgroup analyses were reported but were not prespecified in the trial registry and do not appear to be adjusted for multiple testing (and therefore there is an elevated risk of finding statistical significance when it does not exist):
  • Subgroup analyses: Oxygen requirement. The impact of dexamethasone on reducing mortality was greatest for patients receiving invasive mechanical ventilation, where 28-day mortality was reduced by 35% (29% for those randomized to dexamethasone vs. 40.7% for those receiving standard of care alone, RR 0.65 [95% CI 0.51-0.82]). Twenty-eight-day mortality of patients receiving oxygen without invasive mechanical ventilation was reduced by 20% in response to dexamethasone treatment (21.5% dexamethasone vs. 25% usual care, RR 0.80 [95% CI 0.70-0.92]). There was no reported evidence of clinical benefit of dexamethasone, and while not significant, there was a numerical increase in 28-day mortality rate (17% dexamethasone vs. 13.2% usual care), among patients not receiving respiratory support (rate ratio 1.22 [95% CI 0.93 to 1.61]).
  • Subgroup analyses: Age. Patients <70 years old had a numerically better clinical response to dexamethasone treatment compared to patients aged 70-80 years or 80 years and above, as observed by reduced incidence of mortality at 28-days. Of 1142 patients aged <70 years receiving dexamethasone, 124 died by day 28 (10.9%) compared to 413/2506 patients receiving standard of care (16.5%; [RR 0.64; 0.52-0.78]). For patients aged ≥70 <80, mortality rate at day 28 was 146/467 (31.3%) for those randomized to dexamethasone, compared to 262/860 for those receiving standard of care alone (30.5%). For patients aged ≥80, mortality rate at day 28 was 184/495 (37.2%) for those receiving dexamethasone compared to 390/955 for those receiving standard of care alone (40.8%).
  • Subgroup analyses: Days since symptom onset. Consistent with increased clinical benefit observed for those patients requiring additional oxygen support, dexamethasone treatment had a greater impact at reducing mortality for patients with >7 days since symptom onset at time of trial randomization. 28-day mortality for patients with >7 days since symptom onset: 201/1184 (17.0%; dexamethasone) vs. 581/2507 (23.2%; standard of care) (RR 0.68 [0.58-0.80]). 28-day mortality for patients with ≤7 days since symptom onset: 252/916 (27.5%; dexamethasone), vs. 478/1801 (26.5%; standard of care) (RR 1.01; 0.87-1.17).
  • The study did not perform subgroup analyses on whether the patients received treatment by oral or intravenous (i.v.) administration of dexamethasone. Unlike i.v. administered dexamethasone, oral dexamethasone is only 70-80% bioavailable. It is therefore unknown whether outcomes were affected by differing concentrations of drug according to route of administration.