Fludrocortisone Dosing in Congenital Adrenal Hyperplasia
Most patients with CAH require 50-200 μg of fludrocortisone daily as a single morning dose, with children and younger adults often requiring higher doses up to 200 μg daily, adjusted based on blood pressure, serum electrolytes, and clinical symptoms. 1
Standard Dosing Recommendations
Adults and Adolescents
- The typical starting dose is 100 μg (0.1 mg) daily, with a therapeutic range of 50-200 μg per day 1, 2
- The FDA-approved dosing for salt-losing adrenogenital syndrome (the most common severe form of CAH) is 100-200 μg (0.1-0.2 mg) daily 3
- Administer as a single dose in the morning upon awakening 2
Pediatric Patients
- Children and younger adults typically require higher doses per body surface area than older patients 1, 2
- In a large German/Austrian registry of 1,288 children with classic CAH, 74.1% received fludrocortisone with a median daily dose of 88.8 μg 4
- Most pediatric patients with salt-wasting CAH require mineralocorticoid replacement 5
Dose Adjustment Algorithm
When to Increase Fludrocortisone
- Hyponatremia (low sodium) 2
- Hyperkalemia (high potassium) 2
- Orthostatic hypotension despite adequate sodium intake 2
- Persistent salt cravings 2
When to Decrease Fludrocortisone
- Development of hypertension - reduce dose but do NOT stop completely 1, 2
- Peripheral edema 2
- Supine hypertension 1
Critical Monitoring Parameters
- Blood pressure in both supine and standing positions 2
- Serum sodium and potassium levels 1, 2
- Body weight 1
- Clinical symptoms: salt cravings, lightheadedness, edema 2
Age-Specific Considerations
In children under 8 years of age, fludrocortisone dose is a significant risk factor for hypertension 6. A large cohort study found that 18.5% of young children with CAH had hypertension compared to only 4.9% of adolescents, with fludrocortisone dose per m² correlating significantly with blood pressure until age 8 years 6.
Therefore, in young children:
- Start at the lower end of the dosing range (50-100 μg daily) 1
- Monitor blood pressure carefully and frequently 6
- Adjust dose based on BP response, not just electrolytes 6
Important Clinical Pitfalls to Avoid
Never Stop Fludrocortisone Completely for Hypertension
If essential hypertension develops, reduce the fludrocortisone dose but do not discontinue it 1, 2. Abrupt discontinuation can trigger adrenal crisis with life-threatening hypotension, hyponatremia, and hyperkalemia 2.
Under-Replacement is Common and Dangerous
Under-replacement with fludrocortisone is common and may predispose patients to recurrent adrenal crises 2. Do not be overly conservative with dosing out of fear of hypertension, especially in patients with persistent salt cravings or orthostatic symptoms.
Dietary and Medication Interactions
- Advise patients to take salt and salty foods ad libitum 1, 2
- Avoid potassium-containing salt substitutes marketed as "healthy" alternatives 2
- Avoid liquorice and grapefruit juice - they potentiate mineralocorticoid effects 1, 2
- Diuretics, acetazolamide, carbenoxolone, and NSAIDs should be avoided as they interact with fludrocortisone 2
- Drospirenone-containing contraceptives may require higher fludrocortisone doses due to anti-mineralocorticoid effects 2
Special Situations
Pregnancy
Small adjustments to fludrocortisone doses may be needed during pregnancy, particularly during the last trimester 1, as progesterone has anti-mineralocorticoid effects 2.
Perioperative Management
Add fludrocortisone back when enteral feeding is established after surgery in children 1. During major surgery, focus is on stress-dose hydrocortisone; resume fludrocortisone once oral intake resumes 1.
Follow-Up Schedule
Patients should be reviewed at least annually with assessment of 1:
- Health and well-being
- Weight measurement
- Blood pressure (supine and standing)
- Serum electrolytes (sodium and potassium)
Between visits, patients should monitor for symptoms requiring dose adjustment: new onset salt cravings, dizziness upon standing, or development of ankle swelling 2.