Diuresis. Conceptual image of the effect of diuretics on the kidney. A diuretic is any drug that encourages the excretion of urine. Common diuretics include caffeine and alcohol. Medically, diuretics can be used to treat heart failure, cirrhosis of the liver and hypertension (high blood pressure). The diuretic alleviates the symptoms of these disease by causing sodium and water loss through urine.