Decadron (Dexamethasone) 0.5‑6 mg Tablets: Prescription Long-Acting Corticosteroid with 25× Anti-Inflammatory Potency for Cerebral Oedema, Severe Allergic Reactions, and COVID-19

Information last reviewed: May 2026 — for educational purposes only.

Decadron (dexamethasone) is a synthetic fluorinated corticosteroid with the highest anti-inflammatory potency among commonly used oral glucocorticoids — approximately 25–30 times the potency of cortisol on a milligram-to-milligram basis. This makes smaller absolute doses effective for powerful anti-inflammatory and immunosuppressive indications where prednisone doses would be larger and more burdensome. A critically important characteristic of dexamethasone is its minimal mineralocorticoid activity — unlike cortisol or prednisolone, dexamethasone does not meaningfully bind aldosterone receptors, resulting in minimal sodium retention, oedema, or potassium loss at typical doses. This makes it particularly valuable in cerebral oedema management, where reducing brain swelling without adding excess fluid retention is essential.

Dexamethasone gained worldwide attention through the Oxford RECOVERY trial (2020), which demonstrated that 6 mg/day for 10 days significantly reduced 28-day mortality in hospitalised COVID-19 patients requiring oxygen or mechanical ventilation — the first treatment proven to reduce mortality in COVID-19. The proposed mechanism is dexamethasone's suppression of the cytokine storm (hyper-inflammatory response) that causes severe pulmonary injury in advanced COVID-19. This landmark finding resulted in dexamethasone becoming WHO-recommended standard of care for hospitalized, oxygen-requiring COVID-19 patients.

What Is Dexamethasone?

Dexamethasone is a long-acting glucocorticoid with a biological half-life of 36–54 hours — substantially longer than prednisone (12–36 hours) or cortisol (8–12 hours). This long duration of action means once-daily dosing is typically adequate, and it also means dexamethasone causes more sustained HPA axis suppression per dose interval than shorter-acting glucocorticoids. For the dexamethasone suppression test (DST) used in Cushing's syndrome diagnosis, a 1 mg dose is administered at 11 PM and cortisol is measured at 8 AM: normal adrenal function is suppressed (cortisol <1.8 mcg/dL), while Cushing's syndrome produces failure of suppression (cortisol >1.8 mcg/dL). Dexamethasone is also used as prophylactic anti-emesis in chemotherapy regimens (typically 8–20 mg IV pre-chemo) and as a component of multiple myeloma regimens (Rd: lenalidomide + dexamethasone).

Prescription Status

Dexamethasone is prescription-only in the United States. Its high potency and multiple specialised indications require physician oversight for safe dosing, duration, and tapering. It is not available OTC in any form in the US.

Strengths and Available Forms

• 0.5 mg tablet — used in DST (dexamethasone suppression test); low-dose anti-inflammatory conditions
• 0.75 mg tablet — equivalent to approximately 5 mg prednisone in anti-inflammatory potency
• 1 mg tablet — standard DST dose; also low-dose anti-inflammatory indications
• 1.5 mg tablet
• 2 mg tablet
• 4 mg tablet — commonly used for cerebral oedema (4 mg every 6 hours); anti-emesis (4 mg IV pre-chemo)
• 6 mg tablet — COVID-19 RECOVERY trial dose; once daily × 10 days for oxygen-requiring patients
• Oral solution 0.5 mg/5 mL — for paediatric or liquid-required dosing
• IV/IM injection formulations — hospital use for acute cerebral oedema, status asthmaticus, acute anaphylaxis adjunct; not typically dispensed for community use

Loading dose for vasogenic cerebral oedema (brain tumour): typically 10 mg IV loading dose, then 4 mg every 6 hours PO/IV, tapering as symptoms improve over days to weeks.

Price of Decadron and Generic Dexamethasone

Generic dexamethasone tablets are inexpensive and widely available. The 6 mg short-course COVID-19 regimen (10 tablets) costs very little. Higher-strength tablets for cerebral oedema conditions are also low cost. IV formulations used in hospital are compounded or commercially available at institutional pricing.

Frequently Asked Questions

How does dexamethasone compare to prednisone in potency and how are doses converted?

Dexamethasone has approximately 25–30× the anti-inflammatory potency of cortisol and 6–7× the potency of prednisone on a milligram basis. The standard equipotent dose conversion table approximates: 0.75 mg dexamethasone ≈ 5 mg prednisone ≈ 4 mg methylprednisolone ≈ 5 mg prednisolone ≈ 20 mg hydrocortisone ≈ 25 mg cortisone. Therefore, 6 mg/day dexamethasone (COVID-19 dose) is roughly equivalent to 40 mg/day prednisone in anti-inflammatory effect but with minimal fluid-retaining properties. Dexamethasone's long half-life (36–54 hours) means it needs to be dosed once daily, while prednisone typically requires once or twice daily dosing.

Why does dexamethasone not cause as much fluid retention as other steroids?

Mineralocorticoid activity is responsible for the sodium and water retention and potassium loss seen with cortisol and high-dose prednisone. Dexamethasone binds the mineralocorticoid receptor (MR) with negligible affinity — effectively zero mineralocorticoid activity — because the fluorine substitution at C-9 of the dexamethasone molecule sterically interferes with MR binding. As a result, dexamethasone does not cause significant sodium retention, weight gain from oedema, hypertension, or hypokalaemia at therapeutic doses. This property is exploited in the management of SIADH (dexamethasone does not worsen hyponatraemia), cerebral oedema, and settings where fluid overload would be dangerous.

What was dexamethasone's role in the COVID-19 RECOVERY trial?

The UK RECOVERY (Randomised Evaluation of COVID-19 Therapy) trial — published in NEJM in July 2020 — randomised 6,425 hospitalised COVID-19 patients to either dexamethasone 6 mg once daily for up to 10 days or usual care alone. Among patients requiring invasive mechanical ventilation, mortality was reduced by 35% (29% vs 41%); for those requiring oxygen without ventilation, by 20% (23% vs 26%). Critically, dexamethasone showed no benefit and possible harm in patients not requiring respiratory support — consistent with the hypothesis that dexamethasone benefits only the inflammatory (later) phase of COVID-19 illness, not the initial viral replication phase. This finding changed global COVID-19 treatment protocols and is considered one of the most important clinical trial results of the pandemic era.

← Back to Corticosteroids