List of products in the National Drug Code with proprietary name . Ethacrynic acid is a "water pill" (diuretic) that works in your kidneys to increase the amount of urine you make. This helps your body get rid of extra water. This medication is used to decrease swelling (edema) caused by conditions such as cancer, congestive heart failure, liver disease, and kidney disease. This effect can help your kidneys work better and lessen symptoms such as trouble breathing and swelling in your ankles, feet, hands, or belly. This medication should not be used for infants.