Dexamethasone to Hydrocortisone Injection Dose Conversion
When converting from dexamethasone to hydrocortisone injection, use a potency ratio of approximately 1:100 (dexamethasone to hydrocortisone), meaning 1 mg of dexamethasone equals approximately 100 mg of hydrocortisone. 1
Conversion Ratios
The conversion between these corticosteroids depends on the clinical context:
Standard Glucocorticoid Equivalency
- Dexamethasone is 25 times more potent than hydrocortisone for general anti-inflammatory effects 2
- However, for adrenal suppression and stress coverage, dexamethasone is 80-100 fold (or greater) more potent than hydrocortisone 3
- Dexamethasone 6-8 mg IV provides equivalent coverage to hydrocortisone 200 mg over 24 hours 1, 4, 5
Practical Conversion Guidelines
For perioperative stress coverage:
- Dexamethasone 6-8 mg IV = Hydrocortisone 200 mg/24 hours 1, 4
- This means approximately 0.75-1 mg dexamethasone = 100 mg hydrocortisone in the stress dose context 1
For replacement therapy:
- The standard oral equivalency uses: Dexamethasone 10 mg = Prednisone 60 mg = Methylprednisolone 48 mg 2
- Since prednisone is 4 times more potent than hydrocortisone, 10 mg dexamethasone ≈ 240 mg hydrocortisone for replacement purposes 2
Clinical Application
When Switching from Dexamethasone to Hydrocortisone Injection:
For acute stress/crisis situations:
- If patient received dexamethasone 8 mg IV, switch to hydrocortisone 100 mg IV every 6 hours (400 mg/24 hours total) 4
- Alternatively, use hydrocortisone 200 mg/24 hours as continuous infusion 4
For perioperative coverage:
- Replace dexamethasone 6-8 mg with hydrocortisone 100 mg IM/IV every 6 hours 1, 4
- Continue for 24-48 hours postoperatively, then transition to oral dosing 4
For labor and delivery:
- Use hydrocortisone 100 mg IM initially, followed by 50 mg IM every 6 hours 1
Important Clinical Considerations
Critical Differences Between Agents
Mineralocorticoid activity:
- Dexamethasone lacks mineralocorticoid activity, making it inadequate as sole coverage for patients with primary adrenal insufficiency 1
- Hydrocortisone has mineralocorticoid activity, which is essential in primary adrenal insufficiency 1
- When switching from dexamethasone to hydrocortisone in primary adrenal insufficiency, ensure fludrocortisone is added once enteral feeding is established 4
Duration of action:
- Dexamethasone has a much longer biological half-life than hydrocortisone 2
- Dexamethasone 6-8 mg provides sufficient coverage for 24 hours, while hydrocortisone requires dosing every 6 hours 1, 5
Common Pitfalls to Avoid
- Do not use the 25:1 ratio for stress dosing - this significantly underestimates dexamethasone's potency for adrenal suppression and will result in inadequate hydrocortisone dosing 3
- Avoid dexamethasone for routine replacement therapy in adrenal insufficiency, as it should be avoided in this context 2
- Monitor for excessive glucocorticoid coverage if switching during ongoing treatment, as overlapping doses may cause hyperglycemia 5
- In neonates, recognize that high-dose dexamethasone (0.5 mg/kg/day) is equivalent to at least 15-20 mg/kg/day of hydrocortisone, far exceeding typical replacement doses 2