SPIRONOLACTONE causes increased amounts of sodium and water to be excreted while potassium is retained. Spironolactone acts both as a diuretic and as an antihypertensive drug by this mechanism. It may be given alone or with other diuretic agents that act more proximally in the renal tubule. SPIRONOLACTONE treats high blood pressure and heart failure. It may also be used to reduce swelling related to heart, kidney, or liver disease. It helps your kidneys remove more fluid and salt from your blood through the urine without losing too much potassium. It belongs to a group of medications called diuretics.