What is the equivalent dose of dexamethasone for methylprednisolone 2 mg twice a day?

Methylprednisolone to Dexamethasone Conversion

The equivalent dose of dexamethasone for methylprednisolone 2 mg twice daily is 0.75 mg once daily. 1

Corticosteroid Equivalence Calculation

The conversion between methylprednisolone and dexamethasone is based on their relative potencies:

• Methylprednisolone has a relative potency of 5 compared to hydrocortisone
• Dexamethasone has a relative potency of 25-30 compared to hydrocortisone 1

Therefore:

1. Methylprednisolone 2 mg BID = 4 mg total daily dose
2. Dexamethasone is approximately 5-6 times more potent than methylprednisolone
3. 4 mg methylprednisolone ÷ 5.33 (average potency ratio) = 0.75 mg dexamethasone

Clinical Considerations for Conversion

When converting between corticosteroids, several factors should be considered:

• Duration of action: Dexamethasone has a longer half-life (36-72 hours) compared to methylprednisolone (12-36 hours) 2
• Dosing frequency: Due to its longer half-life, dexamethasone can be administered once daily, while methylprednisolone typically requires multiple daily doses 1
• Mineralocorticoid effects: Dexamethasone has minimal mineralocorticoid effects compared to methylprednisolone

Disease-Specific Considerations

The appropriate conversion may vary depending on the condition being treated:

• For inflammatory conditions, the British Association of Dermatologists suggests that equivalent doses should be maintained when switching between corticosteroids 3
• For COVID-19 pneumonia, some evidence suggests that methylprednisolone may have different clinical effects than equivalent doses of dexamethasone, with one study showing better outcomes with methylprednisolone 4, 5

Practical Application

For a patient currently on methylprednisolone 2 mg twice daily:

• Convert to dexamethasone 0.75 mg once daily
• Monitor clinical response after conversion
• Adjust dosing as needed based on therapeutic response and side effects

Common Pitfalls to Avoid

1. Incorrect potency ratio: Using incorrect relative potency values can lead to under or overdosing
2. Ignoring half-life differences: Failure to account for the longer half-life of dexamethasone may lead to inappropriate dosing frequency
3. Abrupt discontinuation: When switching between corticosteroids for long-term therapy, gradual tapering is recommended to avoid adrenal insufficiency 1

The conversion ratio addresses dose equivalence but not duration of effect, so dosing frequency should be adjusted based on the half-life of the specific steroid.