Overview
Spironolactone is a potassium-sparing diuretic that prevents the body from absorbing too much salt while preventing potassium levels from dropping too low. It is commonly prescribed to treat heart failure, hypertension (high blood pressure), and edema (fluid retention) associated with conditions like liver cirrhosis.

Mechanism of Action
It functions as a competitive antagonist of the aldosterone receptor in the distal convoluted tubule and collecting duct of the nephron. By blocking aldosterone, it promotes the excretion of sodium and water while retaining potassium, reducing fluid volume and lowering blood pressure.

Dosage and Administration
The dosage varies depending on the condition. For edema, the initial adult dose is typically 25 to 200 mg per day in divided doses. For heart failure, it is usually 12.5 to 25 mg once daily. It should be taken with food to increase absorption and reduce gastrointestinal irritation.

Side Effects
Common side effects include hyperkalemia (dangerously high potassium levels), dizziness, headache, and stomach upset. Due to its antiandrogenic properties, it can cause gynecomastia (breast enlargement) in men and menstrual irregularities in women.

Contraindications
It is contraindicated in patients with hyperkalemia, severe kidney failure, or Addison’s disease. Caution is advised when used with other potassium-sparing diuretics, ACE inhibitors, or potassium supplements due to the risk of severe hyperkalemia.

Pregnancy and Lactation
Spironolactone should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. It is excreted in breast milk, so nursing mothers should either discontinue breastfeeding or stop taking the medication.