Known brand names include Aldactone.
A potassium-sparing "water pill" that blocks aldosterone. It treats heart failure with reduced ejection fraction, resistant high blood pressure, swelling from cirrhosis or nephrotic syndrome, and primary hyperaldosteronism.
Spironolactone blocks aldosterone, a hormone that tells the kidneys to hold on to salt and get rid of potassium. It does this by taking the hormone's place on its receptors in a late section of the kidney's filtering tubes. With aldosterone blocked, the kidneys pass more salt and water into the urine while keeping potassium. The body quickly turns it into active breakdown products, such as canrenone, that also block aldosterone.
Losing extra salt and water lowers swelling and blood pressure, and it can be combined with other water pills that act at earlier points in the kidney. It may take about 2 weeks or longer for its full effect to show. Because it makes the body keep potassium, potassium can climb too high, especially with weak kidneys, potassium supplements, salt substitutes, or certain other blood pressure drugs. Losing too much fluid can also cause dehydration, low blood pressure, and worse kidney function.
Spironolactone is a water pill that helps the body hold on to potassium. In advanced heart failure with a weakly pumping heart, it helps people live longer, clears swelling, and keeps them out of the hospital. It is also added for high blood pressure that other drugs have not controlled, and lowering blood pressure cuts the risk of strokes and heart attacks. It controls these conditions but does not cure them.
It treats fluid buildup, called edema, in adults with liver scarring when limiting salt and fluid has not helped, and in a kidney condition called nephrotic syndrome when other treatments fall short. It also treats primary hyperaldosteronism, in which the adrenal glands make too much of the hormone aldosterone, either for a short time before surgery or long term for people who cannot have surgery. In heart failure, it is usually taken along with other heart failure medicines. Its safety and effectiveness in children have not been established.
Breast growth in men is the most common side effect, and it usually goes away after stopping. Irregular periods, breast pain, lower sex drive, upset stomach, dizziness, headache, and drowsiness also happen. The label treats high potassium as the main danger, along with dehydration, low blood pressure, worse kidney function, mineral and blood sugar changes, confusion in people with liver disease, and rare severe skin or blood reactions.