spironolactone

Spironolactone is a potassium-sparing diuretic and a synthetic steroidal antimineralocorticoid. It acts as a competitive antagonist of the mineralocorticoid receptor in the distal tubule and collecting duct, reducing aldosterone-dependent sodium reabsorption and promoting potassium retention. Because of its antiandrogen effects, it has uses beyond diuresis in some conditions.

Medical uses include treatment of edema associated with congestive heart failure, liver cirrhosis with ascites, and nephrotic syndrome; adjunctive therapy for resistant hypertension; and diagnosis or treatment of primary hyperaldosteronism. It is sometimes used in heart failure patients in combination with other diuretics to improve outcomes. Off-label, it is used for polycystic ovary syndrome, androgenic alopecia in women, and acne due to its antiandrogen properties.

Side effects and safety considerations include hyperkalemia, particularly in chronic kidney disease, the elderly, or when used with other potassium-sparing agents or with ACE inhibitors or ARBs. Other common adverse effects are gynecomastia, menstrual irregularities, breast tenderness, and gastrointestinal upset. Dehydration and rash may occur; severe liver injury is rare. Spironolactone is contraindicated in pregnancy because of potential feminization of a male fetus; its use during lactation should be considered carefully.

Pharmacokinetics: it is well absorbed orally and is rapidly hepatically metabolized to active metabolites such as canrenone. The diuretic effect typically begins within 24 to 48 hours, with maximal effect developing over several days.

Monitoring and interactions: potassium and creatinine levels should be regularly checked. Caution is advised with NSAIDs and concomitant potassium-sparing agents or renin–angiotensin system inhibitors.