What is the hydrocortisone (corticosteroid) equivalent dose to 5mg of dexamethasone (glucocorticoid)?

Dexamethasone to Hydrocortisone Dose Equivalency

5 mg of dexamethasone is equivalent to approximately 1,250 mg of hydrocortisone based on the established conversion ratio of 0.1 mg dexamethasone = 10 mg hydrocortisone. 1, 2

Conversion Calculation

Using the guideline-established equivalency ratio:

• 0.1 mg dexamethasone = 10 mg hydrocortisone 1
• Therefore: 5 mg dexamethasone × (10 mg hydrocortisone / 0.1 mg dexamethasone) = 1,250 mg hydrocortisone

This conversion is explicitly confirmed in the guidelines, which state that 8 mg dexamethasone equates to 200 mg hydrocortisone, establishing the 1:25 potency ratio. 1

Clinical Context and Important Caveats

Duration of Action Differences

• Dexamethasone provides prolonged glucocorticoid coverage (24-48 hours) due to its long half-life, whereas hydrocortisone has a plasma elimination half-time of only approximately 90 minutes. 1
• The 6-8 mg dexamethasone dose commonly used for postoperative nausea prophylaxis provides adequate stress coverage for 24 hours, equivalent to 200 mg hydrocortisone. 1

Critical Limitation: Mineralocorticoid Activity

• Dexamethasone has NO mineralocorticoid activity and is therefore inadequate as sole glucocorticoid stress coverage in patients with primary adrenal insufficiency. 1, 2, 3
• Patients with primary adrenal insufficiency require fludrocortisone supplementation when dexamethasone is used. 3

Potency Considerations

• While the anti-inflammatory potency ratio is approximately 1:25 (dexamethasone:hydrocortisone), dexamethasone is 80-100 fold more potent than hydrocortisone in suppressing adrenal androgen production, which is relevant in specific conditions like congenital adrenal hyperplasia. 4

Common Pitfalls to Avoid

• Do not use simple arithmetic conversion when switching between these medications in chronic therapy - the prolonged duration of action of dexamethasone means that 5 mg dexamethasone given once will provide glucocorticoid effect far longer than a single 1,250 mg dose of hydrocortisone. 1
• Do not substitute dexamethasone for hydrocortisone in primary adrenal insufficiency without adding mineralocorticoid replacement. 1, 2, 3
• Do not assume bioequivalence in all clinical scenarios - the pharmacokinetic profiles differ substantially, with hydrocortisone requiring more frequent dosing (every 6 hours for stress coverage) versus dexamethasone's once-daily administration. 1