What is the equivalent dose of hydrocortisone for a patient taking prednisone 10 mg?

Prednisone to Hydrocortisone Conversion

Prednisone 10 mg is equivalent to hydrocortisone 40 mg. 1, 2

Conversion Ratios and Pharmacology

The conversion between different glucocorticoids is based on their relative potency:

• Hydrocortisone is the standard reference glucocorticoid (identical to cortisol)
• Prednisone is approximately 4 times more potent than hydrocortisone 1
• Therefore, the conversion ratio is 1:4 (prednisone:hydrocortisone)

This means:

• 10 mg prednisone = 40 mg hydrocortisone
• 5 mg prednisone = 20 mg hydrocortisone
• 2.5 mg prednisone = 10 mg hydrocortisone

Dosing Considerations

When converting between these medications, several factors should be considered:

Dosing Schedule

• Hydrocortisone has a shorter half-life (approximately 90 minutes) compared to prednisone 1
• While prednisone can often be given once daily, hydrocortisone typically requires multiple daily doses to mimic the natural cortisol rhythm 1
• A common hydrocortisone dosing schedule is:
  • 20 mg in the morning upon awakening
  • 10 mg at midday
  • 10 mg in the late afternoon (not too close to bedtime) 1

Clinical Context

The appropriate dosing may vary based on:

1. Replacement therapy: For adrenal insufficiency, total daily hydrocortisone doses typically range from 15-25 mg 1

2. Anti-inflammatory therapy: For inflammatory conditions, higher doses may be needed initially with subsequent tapering

3. Stress dosing: During periods of physiological stress (surgery, illness), patients on chronic glucocorticoid therapy may require increased doses 1

Important Considerations and Pitfalls

• Mineralocorticoid activity: Hydrocortisone has more mineralocorticoid activity than prednisone, which may affect fluid and electrolyte balance 1

• Timing of administration: For replacement therapy, hydrocortisone should be timed to mimic the natural cortisol rhythm, with the largest dose in the morning 1

• Drug interactions: Medications that affect CYP3A4 enzyme can alter hydrocortisone metabolism, potentially requiring dose adjustments 1

• Tapering: When switching between glucocorticoids or discontinuing therapy, gradual tapering is important to prevent adrenal insufficiency 2

• Liver disease: In patients with active liver disease, conversion of prednisone to prednisolone (its active form) may be impaired, potentially affecting the expected equivalence 3

The conversion from prednisone to hydrocortisone is important in various clinical scenarios including perioperative management, adrenal insufficiency treatment, and when transitioning between different glucocorticoid formulations.