Final answer:
Spironolactone works by antagonizing aldosterone receptors in the distal tubules of the kidney, resulting in increased excretion of sodium and water and decreased excretion of potassium.
Step-by-step explanation:
The mechanism of action of the potassium-sparing diuretic drug spironolactone is the antagonism of aldosterone receptors. Spironolactone works by binding to aldosterone receptors in the distal tubules of the kidney, blocking the action of aldosterone. By inhibiting aldosterone, spironolactone reduces sodium reabsorption and increases potassium retention, resulting in increased excretion of sodium and water and decreased excretion of potassium.