This medicine belongs to the class of medications known as diuretics (water pills). Aldactone works by making the body lose excess water and salt but reduces the loss of potassium from the body. Since this medication increases urine output, it is better to take it early in the day (with breakfast if you are taking a once-daily dose, or with breakfast and lunch if you are taking divided doses). Aldactone is used to treat high blood pressure and edema or swelling from heart, kidney or liver diseases. It is also used to treat patients who have low potassium levels. This medication should be taken only if your doctor prescribed to you. Avoid unnecessary use. Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.