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What are Diuretics

Diuretics (also called 'water pills' or 'fluid pills' ) are drugs that increase urine production in the kidneys, promoting the removal of salt and fluid from the body. Reducing the amount of fluid in the blood vessels results in reduction in blood pressure. There are several types of diuretics. Each type works in a distinct way and in different parts of the kidney.

How they work

Diuretics work in the kidney where it changes how much salt (potassium, sodium or chloride) is reabsorbed, which increases the amount of urine the body produces. There are different types of diuretics that work in specific areas of the kidney and some are more effective than others.

What they treat

Diuretics are used to treat conditions that have fluid retention, such as heart failure, kidney failure and cirrhosis of the liver. They are also effective at reducing blood pressure and so are used in the treatment of hypertension (high blood pressure). Carbonic anhydrase diuretics are mainly used in the treatment of glaucoma and are sometimes used off-label for altitude sickness.

Diuretic Groups 

Thiazide diuretics increases amount of urine produced by reducing sodium re-absorbtion in the kidney. Another effect they have is to widen the blood vessels which also helps reduce blood pressure. Examples are

  • bendroflumethiazide 
  • chlorothiazide
  • chlorthalidone
  • hydrochlorothiazide
  • indapamide
  • metolazone. 

Loop diuretics are powerful diuretics that work in a part of the kidney called the loop of Henle where they reduce sodium, chloride and potassium reabsorption. This increases the amount of urine produced which helps reduce blood pressure and also helps remove any extra fluid that has been accumulating around the body (odema) or the lungs. Examples are

  • bumetanide
  • furosemide
  • torsemide.

Potassium sparing diuretics are weaker diuretics that have their effect by increasing the amount of water and sodium that passes through the kidneys to increase urine volume. Because there is no increase in the amount of potassium that is passed through the kidney sometimes you may end up with higher potassium levels. Examples are

  • amiloride
  • eplerenone
  • spironolactone
  • triamterene

Carbonic anhydrase inhibitors are weaker diuretics that act by increasing the amount bicarbonate, sodium, potassium and water excreted from the kidney. Carbonic anhydrase inhibitors are also used to reduce fluid levels in the eye and is sometimes used off-label for altitude sickness. An example is

  • acetazolamide

Side Effects

Diuretics may cause some side effects which can depend on the type of diuretic taken. Generally the more common side effects of diuretics may include changes in potassium, sodium, calcium or magnesium blood levels, changes in heartbeat, you may have dizziness, headache, tiredness, dry mouth, gastric upset, gout, increase sugar levels or muscles cramps. Related medical conditions: Edema, Congestive heart failure, Hypertension (high blood pressure), Ascites.

Types of Diuretics

Please refer to the drug classes listed below for further information.