Spironolactone is a specific antagonist of the mineralocorticoid receptor in the distal tubules of the kidney. Spironolactone counteracts the actions of aldosterone and thus has a natriuretic and potassium-sparing effect. It is the drug of choice in the treatment of hyperaldosteronism (100-150 mg divided over different doses daily).
I. Spironolactone can be used to treat hypertension due to pheochromocytoma.
II. Hypokalemia is a contraindication for the use of spironolactone.
Extra info: For the preoperative treatment of pheochromocytoma alpha and beta-blocking agents are required. Spironolactone has a potassium-sparing effect and will (partly) cure the hypokalemia. Hyperkalemia is a contraindication.