Prednisone to Hydrocortisone Conversion and Daily Dosing
If 2.5mg of prednisone is equivalent to 10mg of hydrocortisone, then a person taking 2.5mg of prednisone would need 10mg of hydrocortisone as their full daily dose. 1
Conversion Ratio and Equivalence
The conversion between prednisone and hydrocortisone follows a 1:4 ratio:
- 2.5mg prednisone = 10mg hydrocortisone
- 5mg prednisone = 20mg hydrocortisone
- 7.5mg prednisone = 30mg hydrocortisone
This equivalence is clearly established in clinical guidelines for adrenal insufficiency and other conditions requiring glucocorticoid replacement 1.
Physiologic Replacement Considerations
When considering physiologic replacement for adrenal insufficiency:
- The typical full daily hydrocortisone dose ranges from 15-20mg in divided doses 1
- For patients on prednisone, the equivalent physiologic replacement would be 3.75-5mg daily
- A dose of 2.5mg prednisone represents a relatively low replacement dose, equivalent to 10mg hydrocortisone
Administration Patterns
For optimal physiologic replacement with hydrocortisone:
- Hydrocortisone is typically given in divided doses (2/3 in morning, 1/3 in early afternoon) to mimic natural cortisol rhythm 1
- The 10mg hydrocortisone equivalent to 2.5mg prednisone could be given as:
- 7mg in the morning and 3mg in early afternoon
- Or 5mg twice daily
Clinical Implications
When switching between these medications:
- Prednisone has a longer half-life (12-36 hours) compared to hydrocortisone (8-12 hours)
- Prednisone may provide more stable blood levels but less physiologic rhythm
- Hydrocortisone better mimics the natural diurnal pattern but requires multiple daily doses
Monitoring Considerations
When managing patients on either medication:
- Monitor for signs of over-replacement: weight gain, hypertension, hyperglycemia
- Monitor for signs of under-replacement: fatigue, nausea, hypotension
- Adjust dosing based on clinical response rather than laboratory values alone
Special Situations
- During acute illness or stress: Increase dosing by 2-3 times the maintenance dose 1
- For surgical procedures: Higher doses may be required (50-100mg hydrocortisone equivalent)
- Tapering: When discontinuing therapy, gradual tapering is essential to prevent adrenal crisis
Remember that this conversion applies to glucocorticoid effects - mineralocorticoid effects differ between these medications, with hydrocortisone having more mineralocorticoid activity than prednisone.