Spironolactone dose-response relationships in healthy subjects

Area of Science:

• Pharmacology
• Nephrology
• Endocrinology

Background:

• Fludrocortisone administration induces significant urinary electrolyte changes.
• Spironolactone is a known antimineralocorticoid agent.
• Understanding spironolactone's dose-response is crucial for its clinical application.

Purpose of the Study:

• To evaluate the dose-response relationship of spironolactone in reversing fludrocortisone-induced electrolyte alterations.
• To determine the optimal dosage range for spironolactone's antimineralocorticoid activity.
• To assess the dissociation between sodium and potassium excretion responses to spironolactone.

Main Methods:

• Healthy subjects received single oral doses of spironolactone (25-400 mg) or placebo.
• Urinary electrolytes were collected and analyzed during two periods (2-10 h and 12-16 h post-treatment).
• Statistical analysis focused on log-linear dose-response relationships for sodium, potassium, and Na/K ratio.

Main Results:

• Statistically significant log-linear dose-response relationships were observed for sodium excretion, potassium excretion, and the Na/K ratio (P < 0.001).
• Urinary sodium response did not monotonically increase with log spironolactone dose.
• Potassium excretion plateaued between 100-200 mg, with no significant depression at 12-16 h post-treatment compared to placebo (P > 0.1).

Conclusions:

• Sodium and potassium responses to spironolactone are dissociated in terms of maximal effect dose and duration.
• Urinary electrolyte functions or the Na/K ratio alone are insufficient to describe renal antimineralocorticoid activity.
• Dose-response relationships were steep and linear between 25-100 mg spironolactone, suggesting this range for future studies using this model.