What is the equivalent oral dose of hydrocortisone for an adult patient with adrenal insufficiency or a severe inflammatory disorder when transitioning from intravenous (IV) hydrocortisone to oral hydrocortisone?

Transitioning from IV to Oral Hydrocortisone

When transitioning from IV hydrocortisone to oral hydrocortisone in adults with adrenal insufficiency, use a 1:1 dose equivalence and double the patient's usual maintenance dose for 48 hours post-stress, then return to standard maintenance dosing of 15-25 mg/day in divided doses. 1, 2, 3

Immediate Post-Stress Transition Protocol

For patients recovering from major stress or surgery:

• Once the patient is stable and able to take oral medications, discontinue IV hydrocortisone and immediately start oral hydrocortisone at double the usual maintenance dose for 48 hours 1, 2
• After 48 hours, reduce to the patient's standard maintenance regimen 1, 2
• The typical maintenance dose is 15-25 mg/day divided into 2-3 doses (e.g., larger morning dose with smaller afternoon dose to mimic circadian rhythm) 3, 4

Dose Equivalence Considerations

The bioavailability of oral hydrocortisone is essentially complete:

• IV and oral hydrocortisone have approximately 1:1 dose equivalence 5, 6
• However, oral absorption creates peak-and-trough patterns with an elimination half-life of approximately 1.5 hours, requiring multiple daily doses 7, 8
• The FDA label indicates dosing ranges from 20-240 mg/day depending on disease severity, but for adrenal insufficiency replacement, 15-25 mg/day is standard 5, 4

Specific Clinical Scenarios

Post-major surgery or adrenal crisis:

• If the patient was receiving IV hydrocortisone 200 mg/24h continuous infusion, transition to oral hydrocortisone at double the usual maintenance dose (typically 30-50 mg/day in divided doses) for 48 hours 1, 2
• Then reduce to standard maintenance of 15-25 mg/day 3, 4

Post-minor procedures:

• If the patient received a single 100 mg IV dose, transition to double the usual oral dose for 24 hours only, then return to normal maintenance 2

Dosing Schedule for Oral Maintenance

Optimal oral dosing regimen to approximate physiological cortisol:

• Administer in 2-3 divided doses with the largest dose in the morning (e.g., 10 mg at 0730h, 5 mg at 1200h, 5 mg at 1630h) 8
• This mimics the circadian rhythm with higher morning cortisol levels 7, 8
• Avoid evening doses to allow a cortisol-free interval at night 7

Critical Pitfalls to Avoid

Do not abruptly stop IV hydrocortisone without oral coverage:

• Ensure the patient can tolerate oral intake before discontinuing IV therapy 1, 2
• If prolonged nil-by-mouth status is anticipated, continue IV dosing 1

Do not forget mineralocorticoid replacement in primary adrenal insufficiency:

• Add fludrocortisone 0.05-0.3 mg/day once enteral feeding is established in patients with Addison's disease 3, 4
• Secondary adrenal insufficiency does not require fludrocortisone as aldosterone production is preserved 3

Monitor for inadequate replacement:

• Current immediate-release oral formulations result in suboptimal plasma cortisol profiles, with 45-79% of patients over- or under-treated at various time points throughout the day 8
• Clinical signs of under-replacement include fatigue, hypotension, and hypoglycemia 4
• Signs of over-replacement include weight gain, hyperglycemia, and cushingoid features 8

Pediatric Considerations

For children transitioning from IV to oral:

• Once stable, administer double the usual oral doses for 48 hours, then reduce to normal doses over up to one week 1, 2
• Standard pediatric maintenance dosing is 0.56-8 mg/kg/day in 3-4 divided doses (20-240 mg/m²/day) 6