Name: Spironolactone (Aldactone)
Class: Diuretic (Potassium Sparing Diuretic) (Aldosterone Antagonist)
Mechanism: Competitive inhib. of aldosterone ® block of aldost.-stim. Na+ reabsorption and K+/H+ excretion in late distal tubule and collecting duct. Also reduces aldost.-stim. ammoniagenesis throughout the nephron.
Absorption: Oral. Takes up to 2 days to be effective.
Dist.:
Metabolism.: Hepatic.
Excretion, t½: 20 hr.
Toxicity/S.E.s: Hyperkalemia, gynecomastia, amenorrhea. Absolutely contraindicated w/hyperkalemia.
Utility: Most efficacious in pts. w/high plasma levels of aldosterone (e.g., 1° hyperaldosteronism due to an adrenal tumor or hyperplasia; 2° hyperaldost. due to cirrhosis, etc.).
Special Features: Only diuretic that acts through the blood side of the tubule. Rel. weak diuretic.