Adjusting Fludrocortisone Dose in Adult Adrenal Insufficiency Based on Sodium and Potassium
Fludrocortisone dose should be adjusted based on serum electrolytes, blood pressure, and clinical symptoms, with most patients requiring 50-200 μg daily as a single morning dose, increasing when sodium is low or potassium is high, and decreasing when hypertension develops. 1
Baseline Dosing
- Most patients with primary adrenal insufficiency (PAI) should take 50-200 μg fludrocortisone as a single daily dose 1
- Children and younger adults may require higher doses (up to 500 μg daily) 1
- The dose should be taken in the morning upon awakening 1
Monitoring Parameters for Dose Adjustment
- Serum sodium and potassium levels (primary laboratory parameters) 2
- Blood pressure in both supine and standing positions 1
- Clinical symptoms: salt cravings, lightheadedness, peripheral edema 1
- Plasma renin activity (PRA) can be used as a supplementary marker 2, 3
Dose Adjustment Algorithm Based on Electrolytes
When to Increase Fludrocortisone Dose:
- Hyponatremia (serum sodium below normal range) 2
- Hyperkalemia (serum potassium above normal range) 2
- Elevated plasma renin activity 2, 3
- Orthostatic hypotension or persistent salt cravings despite adequate sodium intake 1
When to Decrease Fludrocortisone Dose:
- Development of essential hypertension (dose should be reduced, but not stopped) 1
- Hypokalemia (serum potassium below normal range) 3
- Peripheral edema 1
- Suppressed plasma renin activity with normal electrolytes 3
Special Considerations
- Under-replacement with fludrocortisone is common and may predispose patients to recurrent adrenal crises 1
- Patients should be advised to take salt and salty foods ad libitum 1
- Avoid potassium-containing salt substitutes which are often marketed as "healthy" 1
- Avoid liquorice and grapefruit juice as they potentiate the mineralocorticoid effect of hydrocortisone 1
Medication Interactions Requiring Dose Adjustment
- Diuretics, acetazolamide, carbenoxolone, and NSAIDs should be avoided as they interact with fludrocortisone 1
- Drospirenone-containing contraceptives may require higher fludrocortisone doses 1
- Pregnancy, particularly in the third trimester, may require increased fludrocortisone due to progesterone's anti-mineralocorticoid effects 1
Monitoring Schedule
- Patients with PAI should be reviewed at least annually 1
- Assessment should include measurement of weight, blood pressure, and serum electrolytes 1
- The timing of blood sampling for PRA is not critical when monitoring fludrocortisone replacement 3
Common Pitfalls to Avoid
- Stopping fludrocortisone completely when hypertension develops (reduce dose instead) 1
- Normalizing elevated PRA may lead to overtreatment with symptoms of mineralocorticoid excess (hypokalemia, edema) 3
- Optimal fludrocortisone replacement may be associated with mildly elevated PRA levels 3
- Failing to adjust fludrocortisone during pregnancy or periods of increased physical stress 1, 4
Remember that fludrocortisone dose requirements may decrease over time in patients with longer follow-up (>60 months), so regular monitoring remains important even in stable patients 2.