What Are Diuretics?

Reviewed by: HU Medical Review Board | Last reviewed: March 2022 | Last updated: March 2023

Diuretics, also known as water pills, signal the kidneys to remove salt and water from the body. This aids in the reduction of swelling that commonly occurs in heart failure.1 Diuretics taken as prescribed are considered safe and used to treat multiple conditions that involve fluid accumulation including hypertension, heart failure, kidney failure, cirrhosis of the liver, and glaucoma.2

Diuretics to treat heart failure

There are different classes of diuretics and each works in a distinct way in the kidneys to remove fluid buildup from the body which reduces pressure on blood vessel walls.2-3 As the kidneys eliminate the excess water from the blood, the total blood volume that the heart has to pump is reduced, which causes blood pressure to go down and makes it easier for the heart to pump forward.4

The different kinds of diuretics include carbonic anhydrase inhibitors, loop diuretics, potassium-sparing diuretics, and thiazide diuretics.3

Loop diuretics are the preferred diuretic for use in patients with heart failure. They are also used to treat hypertension and edema due to chronic kidney disease.4 They cause the kidneys to excrete more urine, decreasing the volume of water in the body thus lowering blood pressure.4

Potassium-sparing diuretics, like an aldosterone antagonist, also reduce the amount of water in the body without also losing potassium.4 They are often prescribed with another diuretic to better control blood pressure and to help prevent low potassium levels.4

Carbonic anhydrase inhibitors help remove sodium, potassium, and water from the kidneys. Relatively weak diuretics, they are also are effective at reducing fluid levels in the eyes and are prescribed to treat glaucoma and sometimes used off-label to treat altitude sickness.4

Thiazide diuretics can also be prescribed for heart failure. They are relatively weak drugs which act to decrease the amount of sodium reabsorbed back into the body. This causes increased fluid elimination as urine.2 This type of diuretic reduces the amount of salt and water in the body and widens blood vessels to lower blood pressure. Thiazide diuretics are often the first medication prescribed to treat high blood pressure.4 Make sure to let your cardiologist know if you have gout, diabetes, or lupus as thiazide diuretics can worsen these conditions.

Why are they prescribed?

Prescribed for people with heart failure and high blood pressure, diuretics reduce fluid retention resulting in symptom improvements such as difficulty breathing and swelling. They help people to feel better. They help to regulate the salt and water balance of the body. These drugs increase the elimination of these fluids, allowing the kidneys to get rid of extra water. Diuretics will cause an increased frequency in urination; the reason that diuretics are referred to water pills.1-2

Diuretics are a class of drugs often used for people who take other heart failure medications including ACE inhibitors or ARBs, beta-blockers, other diuretics, and digoxin.1,3 They lower the pressure in the blood vessels, ease the workload on the heart, can relieve shortness of breath, and reduce swelling and bloating.

Diuretics treatment goals

The main goal of diuretics is to reduce the amount of fluid in the body. This leads to symptom relief, lower blood pressure and a decreased risk of hospitalization for heart failure.2

Commonly prescribed diuretics include:2-3

  • Aldactone®, CaroSpir® - (spironolactone)
  • Aquazide H®, Microzide®- (hydrochlorothiazide HCTZ)
  • Bumex®- (bumetanide)
  • Demadex®- (torsemide)
  • Diamox®– (acetazolamide)
  • Diuril®- (chlorothiazide)
  • Dyrenium®- (triamterene)
  • Edecrin®- (ethacrynic acid)
  • Lasix®- (furosemide)
  • Lozol®- (indapamide)
  • Midamor®- (amiloride)
  • Mykrox®, Zaroxolyn®- (metolazone)
  • Thalitone®- (chlorthalidone)

There are different dosages for each of these formulations, and people with HF may be prescribed different dosages at different points to manage their symptoms.

Common side effects of diuretics

Common side effects of diuretics include muscle weakness, fatigue, or low potassium. Most people experience an increased frequency of urination. Medications can take time to work properly and get adjusted. Diuretics tend to work quickly and doses may need to be adjusted frequently. If you find that frequently going to the bathroom interferes with your sleep or certain activities, talk to your doctor about adjusting the medication schedule.1

Various diuretics may have drug interactions with other medicines you are taking. Be sure to mention to your doctor all medications, vitamins, minerals, over the counter products, or herbal supplements you take including:4

  • Antidepressants, if you take thiazide or loop-acting diuretics
  • Cyclosporine, if you take potassium-sparing diuretics
  • Digitalis, if you have low potassium levels
  • Lithium
  • Other high blood pressure drugs

Depending on the diuretic prescribed some people may need to take a potassium supplement or make dietary changes. Your health care provider will decide whether or not you should take potassium.1 As with most heart failure medications, your doctor will generally order regular blood tests to evaluate its effectiveness and any side effects.1

It is important to take all medicines as prescribed. This will improve the effectiveness of the medication and may reduce any complications. If you have difficulty taking medications, do not stop on your own, contact your health care team for assistance.

These are not all the possible side effects of diuretics. Patients should talk to their doctor about what to expect with treatment with diuretics.

If you have trouble breathing, swelling in your face, lips, tongue or throat, or sudden chest pain call 911 or other emergency services or go directly to an emergency room.

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