Pharmacology · Corticosteroids (glucocorticoids)
Fludrocortisone !
A corticosteroid used for its strong salt-retaining (mineralocorticoid) effect, to replace aldosterone when the adrenal glands fail.
Updated 2026-11-01
The figure shows aldosterone, the natural hormone, in the ligand-binding domain of the human mineralocorticoid receptor; fludrocortisone mimics it in the same pocket.
Mechanism of action
Fludrocortisone is a 9α-fluorinated cortisol with very strong mineralocorticoid activity. It binds the mineralocorticoid receptor in the distal tubule and collecting duct; the receptor changes gene transcription so that more sodium channels and Na+/K+-ATPase are made. Sodium and water are reabsorbed and potassium and hydrogen ions are lost in the urine. At replacement doses its glucocorticoid effect is usually not important.
- Fludrocortisone binds the mineralocorticoid receptor in the distal nephron
- More sodium channels and Na+/K+-ATPase are made
- Sodium and water are kept; potassium is excreted
- Blood volume and blood pressure rise
Pharmacokinetics
- Absorption
- Given by mouth as tablets
- Metabolism
- In the liver; enzyme inducers speed its clearance
Indications
- Primary adrenal insufficiency (Addison disease), together with hydrocortisone Adrenal insufficiency →
- Salt-losing congenital adrenal hyperplasia
Adverse effects
Common
- Fluid retention and oedema
- High blood pressure
- Hypokalaemia
- Headache
Contraindications
- Systemic fungal infections
- Hypersensitivity to the product
Key interactions
- Amphotericin B or potassium-depleting diuretics (thiazides, furosemide)
- Greater hypokalaemia
- Digoxin
- More arrhythmias and digoxin toxicity if potassium falls
- Barbiturates, phenytoin, rifampicin
- Faster clearance and weaker effect
- Oral anticoagulants
- Prothrombin time response may fall; it is monitored
- Oestrogens
- More binding globulin, so the corticosteroid dose may need lowering
What is monitored
- Blood pressure, including lying and standing
- Serum potassium and sodium
- Weight and oedema
Administration and safety
- Given by mouth, usually alongside a glucocorticoid in Addison disease
- In stress (surgery, trauma, severe illness) extra corticosteroid cover may be needed, as ordered
Nursing care
- Check blood pressure and weight; report rapid weight gain or swelling
- Check potassium; watch for muscle weakness or cramps
- Teach the patient to carry identification stating steroid dependence
- Ask about dizziness, severe headache or shortness of breath
Pregnancy and breastfeeding
Replacement in adrenal insufficiency continues in pregnancy when needed; the dose is reviewed with blood pressure and electrolytes.
Test yourself
Think of the answer, then tap the question to see it.
Why does a patient with Addison disease often need fludrocortisone besides hydrocortisone?
Primary adrenal failure loses aldosterone too; fludrocortisone replaces the mineralocorticoid effect that keeps sodium and removes potassium.
Which electrolyte disturbance does excess fludrocortisone cause?
Hypokalaemia with metabolic alkalosis, plus sodium and water retention with hypertension and oedema.
Is fludrocortisone needed in secondary (pituitary) adrenal insufficiency?
Usually not: aldosterone is controlled mainly by the renin-angiotensin system, not ACTH, so it is preserved.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Fludrocortisone Acetate: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2017); DailyMed - FLUDROCORTISONE ACETATE tablet (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 39 (McGraw Hill, 2025).
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Representative model, for educational purposes only.