Duration of Fludrocortisone Effect After Discontinuation
Fludrocortisone has a biological half-life of 18 to 36 hours, meaning its mineralocorticoid effects on blood pressure and electrolyte balance persist for approximately 1.5 to 3 days after the last dose. 1
Pharmacokinetic Profile
The FDA drug label provides clear pharmacokinetic data for fludrocortisone:
The biological half-life is the clinically relevant parameter, as it reflects how long the drug's physiological effects on sodium retention, potassium excretion, and blood pressure persist after discontinuation.
Clinical Evidence of Washout Period
Research studies examining fludrocortisone withdrawal provide practical insights into the timeline:
- 1-2 weeks post-discontinuation: In patients with Addison's disease who stopped fludrocortisone, plasma renin activity and angiotensin II levels rose markedly, and hyperkalaemia developed in all patients after 1-2 weeks of withdrawal 2
- Electrolyte changes: The development of hyperkalemia and changes in sodium balance occurred within this 1-2 week timeframe, indicating loss of mineralocorticoid effect 2
Practical Clinical Implications
For Monitoring After Discontinuation
- Days 1-3: Residual mineralocorticoid activity present due to biological half-life 1
- Week 1-2: Full loss of drug effect becomes apparent with rising plasma renin activity, potential hyperkalemia, and orthostatic symptoms 2
- Beyond 2 weeks: Complete washout achieved, with maximal physiological changes from withdrawal evident 2
Important Caveats
For patients with primary adrenal insufficiency, fludrocortisone should never be routinely discontinued or tapered, as mineralocorticoid replacement is lifelong and essential for maintaining blood pressure and electrolyte homeostasis. 3 The drug is replacement therapy, not suppressive therapy, and patients with Addison's disease require continuous treatment 3
If fludrocortisone must be temporarily held (e.g., for diagnostic testing), expect the full mineralocorticoid effects to dissipate within 2-4 days based on the biological half-life, with complete physiological changes evident by 1-2 weeks 1, 2.