Fludrocortisone is the drug of choice for primary adrenal insufficiency (Addison's disease) as mineralocorticoid replacement. Compared to hydrocortisone, fludrocortisone has:

• A Pure mineralocorticoid activity with no glucocorticoid activity at any dose
• B 10-fold lower mineralocorticoid potency than aldosterone and is therefore given in gram doses
• C Equivalent mineralocorticoid and glucocorticoid potency to dexamethasone with additional aldosterone-like activity
• D Approximately 125-fold greater mineralocorticoid potency and 15-fold greater glucocorticoid potency compared to hydrocortisone, making it unsuitable as sole replacement but appropriate for mineralocorticoid supplementation ✓

Explanation

Fludrocortisone (9-alpha-fluorohydrocortisone) has potent mineralocorticoid activity (~125 times hydrocortisone) and significant glucocorticoid activity (~15 times hydrocortisone). In Addison's disease it is given at 0.05–0.2 mg/day to replace aldosterone-like activity; at these doses its glucocorticoid contribution is minor and patients still require separate hydrocortisone replacement (usually 15–25 mg/day). This dual receptor activity distinguishes it from pure mineralocorticoids.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.