Diuretics and Potassium

Diuretics are a common, inexpensive, and effective medication used to treat high blood pressure. Diuretics work by causing the kidneys to increase the amount of salt and water excreted from the body. Over time, this increased excretion causes plasma volume to decrease, which reduces the volume of the liquid contained within the arteries. This decreased volume, in turn, reduces the amount of “pushing” caused by the blood on the artery walls, leading to a decrease in blood pressure.

Some common diuretics include:

• Hydrochlorothiazide
• Furosemide
• Spironolactone
• Amiloride

As a result of increased water and salt removal, most diuretics also cause the body to lose potassium. This can be problematic because potassium is important in regulating blood vessel tone, blood pressure, and the pumping action of the heart.

Different strategies are used to minimize the potassium loss that occurs as a side effect of using diuretics. Sometimes an ACE inhibitor is prescribed along with the diuretic, because ACE inhibitors cause the retention of potassium. In other cases, special kinds of diuretics –- called potassium sparing diuretics -– are used. Unlike other diuretics, these drugs do not increase the amount of potassium lost from the body. Some potassium sparing diuretics include:

• Amiloride
• Spironolactone
• Triamterene

If you’re taking a diuretic and have low potassium, your doctor might try adding an ACE inhibitor or switch you to one of the potassium sparing diuretics. In the majority of cases, one of these two steps will resolve the problem. If your potassium remains low after making these changes, you may need to increase the amount of potassium in your diet, or have simple blood tests to make sure that the problem is not being caused by some underlying condition like a hormone imbalance.