IV Dexamethasone to Oral Prednisolone Conversion
Use a conversion ratio of 1 mg dexamethasone = 6.67 mg prednisolone (approximately 1:7 ratio) when transitioning from IV dexamethasone to oral prednisolone. 1, 2
Standard Conversion Calculation
- The FDA-approved equivalency table indicates that 2.25 mg dexamethasone equals 15 mg prednisolone, yielding a 1:6.67 conversion ratio. 1
- For practical dosing, round to a 1:7 ratio (1 mg dexamethasone = 7 mg prednisolone) for ease of calculation. 1
- This conversion applies specifically to oral or intravenous administration; intramuscular or intra-articular routes may alter relative potencies. 1
Example Conversions:
- 4 mg IV dexamethasone = approximately 28 mg oral prednisolone 1
- 8 mg IV dexamethasone = approximately 56 mg oral prednisolone 1
- 20 mg IV dexamethasone = approximately 140 mg oral prednisolone 1
Post-Pulse Transition Protocol
When transitioning from high-dose IV dexamethasone pulse therapy to oral prednisolone maintenance:
- Start oral prednisolone at 0.5-1 mg/kg/day (maximum 60 mg/day) after completing IV pulse therapy, regardless of the exact dexamethasone dose used. 3, 4
- Maintain the initial high dose for approximately 1 month before beginning tapering to ensure adequate disease control. 3
- Do not reduce the oral dose below 15 mg/day during the first 3 months of treatment for conditions like vasculitis. 3, 4
Tapering Schedule
- Begin tapering after the first month by reducing prednisolone by 5-10 mg weekly until reaching 20 mg daily. 3, 4
- Below 20 mg daily, taper more slowly (1-2.5 mg decrements every 1-2 weeks) to minimize relapse risk. 3
- Complete tapering typically occurs over 3-6 months depending on clinical response and disease severity. 3, 4
Pharmacokinetic Considerations
- Dexamethasone has a significantly longer half-life (approximately 190 minutes) compared to prednisolone (approximately 100 minutes), which explains its more prolonged immunosuppressive effects. 2
- Both medications demonstrate similar bioavailability when given orally (>80%), making oral prednisolone an appropriate maintenance option after IV dexamethasone. 5, 2
- The receptor-binding affinity of dexamethasone is approximately 5-7 times higher than prednisolone, which correlates with the dose equivalency ratio. 2, 6
Common Pitfalls to Avoid
- Do not use a 1:1 conversion ratio between dexamethasone and prednisolone, as this will result in significant underdosing. 1, 2
- Avoid abrupt discontinuation after long-term therapy; always taper gradually to prevent adrenal insufficiency. 1
- Do not assume methylprednisolone and prednisolone are equivalent; methylprednisolone is approximately 1.25 times more potent than prednisolone. 3, 1
- Monitor for disease rebound during the first 2-4 weeks after transitioning from IV to oral therapy, as this is when relapse risk is highest. 3
Monitoring Requirements
- Assess for signs of disease recurrence during tapering, particularly when reducing below 20 mg/day prednisolone. 3
- Monitor for steroid-related adverse effects including hyperglycemia, hypertension, weight gain, and bone density loss. 3
- Consider prophylaxis for Pneumocystis jiroveci pneumonia and gastric protection with proton pump inhibitors during prolonged high-dose therapy. 7, 8
- Implement bone protection strategies (calcium 1000-1500 mg/day, vitamin D 800-1000 IU/day) if therapy is anticipated to exceed 3 months. 8