Dexamethasone

Glucocorticoid·Endocrinology - Systemic Corticosteroids

Cerebral oedema, severe croup, multiple myeloma, severe COVID-19, antiemetic

Authority requiredPBSSTEROIDDexmethsone, Decadron0.5 mg tablet+2

Max Dose

Variable

Half-life

36-54 h

Mineralo. Effect

ZERO

Psychiatric SE

HIGH RISK

Rapid Summary

Overview

Ultra-potent, long-acting synthetic glucocorticoid. 25-30 times more potent than Hydrocortisone. Brilliant brain penetration and absolute zero fluid-retaining (mineralocorticoid) activity.

Maximum Dose

Max varies widely (e.g., 40 mg/day for myeloma, 4-8 mg for antiemetic).

Clinical Focus

The absolute drug of choice for cerebral oedema (brain tumors) and severe pediatric croup.

Bottom Line

Dexamethasone is the most potent long-acting corticosteroid for cerebral oedema, croup, and CINV prophylaxis, but even short courses cause significant hyperglycaemia and long-term use has devastating metabolic effects.

Formulation & Access

Brand Names

Dexmethsone, Decadron

Oral Routes

Tablets (0.5 mg, 4 mg). Oral liquid.

Parenteral

Ampoules (4 mg/1 mL, 8 mg/2 mL) for IV / IM.

Prescribing & PBS

Authority Required (PBS).

Indications & Use

Primary

PBSTGA

Cerebral oedema, severe croup, multiple myeloma, severe COVID-19, antiemetic.

Clinical Place

Reserved for when intense, long-lasting anti-inflammatory power is needed without ANY salt/water retention.

Quick reference

Class & Role

Glucocorticoid — Ultra-potent, long-acting synthetic glucocorticoid.

Route / Formulation

Tablets (0.5 mg, 4 mg). Oral liquid. (Dexmethsone, Decadron)

Usual Dose & Max

IV / PO 4-16 mg/day in divided doses. Max varies widely (e.g., 40 mg/day for myeloma, 4-8 mg for antiemetic).

Key Indication Doses

Cerebral Oedema (Tumor): IV / PO 4-16 mg/day in divided doses. Croup (Paediatric): PO 0.15 mg/kg STAT as a single dose (Max 12 mg). Chemotherapy Antiemetic: PO / IV 4-8 mg given prior to chemo. COVID-19 (Severe): PO / IV 6 mg OD for 10 days.

Best Uses

Avoid / Cautions

Systemic fungal infections, live vaccines. Pregnancy Category A/C. (Unlike Prednisolone, Dexamethasone actively crosses the placenta. Intentionally used to mature fetal lungs in premature labour, but avoid chronic use).

Key Risks

Metabolic: Extreme hyperglycemia (often requires insulin on the ward), Cushing's syndrome. Neurological: Steroid-induced psychosis, mania, severe insomnia, delirium. Immunological: Profound immunosuppression (risk of thrush, severe infections). Musculoskeletal: Proximal myopathy (muscle wasting), avascular necrosis.

Key Interactions

NSAIDs (Massive risk of bleeding gastric ulcers).

Monitoring

Strict BSL checks. Even non-diabetic patients can hit sugars of 20+ on high doses of Dex. Give morning doses only (unless antiemetic) to prevent severe insomnia.

Clinical Pearl

Hydrocortisone causes water retention. If you have a brain tumor, holding onto water increases brain swelling and kills you. Dexamethasone has zero water retention, aggressively shrinking the brain swelling instead. That is why it is the only steroid used in neurosurgery.

Access

Authority requiredDexmethsone, Decadron0.5 mg tablet

Brand: Dexmethsone, Decadron
PBS status: Authority required
Formulation: Tablets (0