Diuretics are a major class of blood pressure medications, often used as a first-line treatment of hypertension. Diuretics, also known as "water pills," cause the kidneys to dump more fluid from the blood into the urine, thus lowering blood volume and blood pressure. There are several classes of diuretics, with different mechanisms of action and indications.
Hydrochlorothiazide and the Thiazide Diuretics
The kidney is made up of many tiny tubes called nephrons that filter the blood. Thiazide diuretics inhibit salt transporters located toward the far end of the nephrons. These are one of the most commonly used classes of diuretics. In addition to the treatment of high blood pressure, they may be used to treat swelling or congestive heart failure. Side effects include lowering the blood pressure too much, low potassium, increased blood glucose, fat and cholesterol, as well as impotence. Examples of drugs in this class include hydrochlorothiazide and chlorthalidone.
Furosemide and the Loop Diuretics
These medications are potent diuretics. They include furosemide, bumetanide and ethacrynic acid. Loop diuretics also inhibit electrolyte transporters in the nephrons. They may be used for high blood pressure, swelling, congestive heart failure or fluid on the lungs. They can also cause low potassium and other electrolytes, dehydration and low blood pressure.
Spironolactone and the Potassium Sparing Diuretics
Because a major side effect of other classes of diuretics is the loss of potassium, it helps to have potassium-sparing diuretics such as spironolactone, amiloride and triamterene. The combination of this class with another tends to keep potassium level even. Conditions they treat are similar to the others. A potential side effect can be dangerously high potassium, which can cause potentially fatal heart rhythms.
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