What is the equivalent dose of prednisolone (corticosteroid) to dexamethasone (corticosteroid) in a patient requiring corticosteroid therapy?

Prednisolone to Dexamethasone Dose Equivalency

The standard conversion ratio is 5:1, meaning 5 mg of prednisolone equals approximately 1 mg of dexamethasone. 1, 2, 3

Standard Conversion Ratios

The following equivalencies are established by authoritative guidelines:

• Prednisolone 5 mg = Dexamethasone 1 mg 2
• Prednisolone 20 mg = Dexamethasone 4 mg 2, 3
• Prednisolone 60 mg = Dexamethasone 10 mg 2

These ratios are based on the fundamental principle that dexamethasone is approximately 5 times more potent than prednisolone in terms of glucocorticoid activity. 2

Pharmacologic Basis

The conversion is rooted in relative potency to hydrocortisone:

• 10 mg hydrocortisone = 2.0 mg prednisolone = 0.1 mg dexamethasone 1
• This establishes dexamethasone as 25 times more potent than hydrocortisone, while prednisolone is 5 times more potent than hydrocortisone 2
• The FDA drug label confirms that 15 mg prednisolone is equivalent to 2.25 mg dexamethasone 3

Critical Clinical Considerations

Dosing Strategy

• Dexamethasone should be given as a single daily dose rather than divided doses 2
• A single 8 mg dose of dexamethasone provides glucocorticoid coverage equivalent to 200 mg hydrocortisone for 24 hours 1

Important Limitations

• Dexamethasone has NO mineralocorticoid activity, making it inadequate for stress coverage in patients with primary adrenal insufficiency 1
• In such patients, hydrocortisone or prednisolone (which have mineralocorticoid effects) must be used 1

Context-Specific Adjustments

• For perioperative conversion: Prednisolone 30 mg oral = Dexamethasone 6 mg IV 2
• When converting between oral and IV routes, bioavailability differences are minimal as both have excellent oral absorption 1

Common Pitfalls to Avoid

• Do not use the 5:1 ratio for intramuscular or intra-articular administration, as relative potencies change significantly with these routes 3
• Monitor for hyperglycemia more closely with dexamethasone, particularly at higher doses 2
• Consider increased infection risk with either agent, but dexamethasone's longer half-life (36-54 hours) means prolonged immunosuppression compared to prednisolone 2
• Avoid confusing methylprednisolone with methylprednisone when making conversions 2

Practical Conversion Examples

For common clinical scenarios:

• Prednisolone 10 mg daily → Dexamethasone 2 mg daily 2
• Prednisolone 40 mg daily → Dexamethasone 8 mg daily 1, 2
• Prednisolone 1 mg/kg (e.g., 70 mg) → Dexamethasone 14 mg 2

The 5:1 conversion ratio has been validated across multiple clinical contexts including perioperative management, inflammatory conditions, and immunosuppression, making it the most reliable standard for clinical practice. 1, 2, 3