Potassium-sparing Diuretics

Potassium-sparing diuretics are weak diuretics. They are most often prescribed in combination with thiazides or loop diuretics, to prevent hypokalaemia (low amounts of potassium in the blood) or to increase the amount of fluid removed from the body. Side-effects are uncommon when routine low doses are used. Most people are able to take these medicines.

What are potassium-sparing diuretics?

A diuretic is a medicine which increases the amount of water that you pass out from your kidneys. (A diuretic causes a diuresis - an increase in urine.) So, they are sometimes called water tablets. There are different types of diuretics. Potassium-sparing diuretics are one type; they include amiloride and triamterene. There are two other medicines which are also potassium-sparing diuretics: eplerenone and spironolactone. These medicines work in a slightly different way to amiloride and triamterene. They are sometimes referred to as aldosterone antagonists.

Other types of diuretics include loop diuretics (for example, furosemide) and thiazide diuretics (for example, bendroflumethiazide). Potassium-sparing diuretics come in different brand names and are also available as combined tablets, with loop diuretics and thiazide diuretics.

How do potassium-sparing diuretics work?

Amiloride and triamterene work by making the kidneys pass out more fluid. They do this by interfering with the transport of salt and water across certain cells in the kidneys. As more fluid is passed out by the kidneys, less fluid remains in the bloodstream. So any fluid which has accumulated in the tissues of the lungs or body is drawn back into the bloodstream to replace the fluid passed out by the kidneys. This eases symptoms such as oedema (fluid retention in legs) and breathlessness caused by the congestion of fluid. As well as increasing the amount of water that you pass out from your kidneys, potassium-sparing diuretics also help your kidneys retain (keep) potassium in the body.

As stated above, eplerenone and spironolactone work in a slightly different way to amiloride and triamterene. These medicines block the action of a hormone called aldosterone and this causes the kidney to pass out more fluid and keep potassium. This is why they are sometimes referred to as aldosterone antagonists.

When used on their own, potassium-sparing diuretics are weak diuretics. Loop diuretics and thiazide diuretics are stronger than potassium-sparing diuretics with regards to making the kidneys pass out more fluid. However, they also increase the amount of potassium passed out of the body through the kidneys.

Potassium-sparing diuretics are often combined with either a loop diuretic or a thiazide diuretic. This is because they help to keep the right amount of potassium in your blood and they help other diuretics to remove fluid from the body.

What are potassium-sparing diuretics used for?

Potassium-sparing diuretics (amiloride, and triamterene) are weak diuretics, most often prescribed in combination with thiazides or loop diuretics, to prevent hypokalaemia (low amounts of potassium in the blood)

Aldosterone antagonists (spironolactone and eplerenone) are prescribed with other diuretics to increase the amount of fluid removed from the body and to prevent hypokalaemia.

Diuretics are commonly used in the treatment of heart failure. In this condition, fluid accumulates in your body, due to the heart not pumping blood around the body as well as it normally would. So, you may become breathless (as fluid accumulates in the lungs) and your ankles and legs may swell with extra fluid in the tissues (oedema). Diuretics are also used to treat other conditions which cause fluid to build up in the body, such as certain liver and kidney disorders and high blood pressure. (But, a thiazide diuretic is more commonly used to treat high blood pressure.)

What are the possible side-effects?

Side-effects are uncommon when routine low doses are used. The higher the dose, the greater the risk of side-effects developing. The leaflet which comes in the tablet package provides a full list of possible side-effects. The more common or serious possible side-effects are listed below:

Amiloride and triamterene

Possibe side effects include: stomach upset, stomach ache or cramp, dry mouth, dizziness or feeling faint, especially when getting up from sitting or lying down (due to too low blood pressure). Other side-effects that have been reported include: skin rash, feeling sleepy or confused, headache, aches and pains, muscle cramps, weakness, diarrhoea or constipation.

Spironolactone and eplerenone

Possible side effects include: feeling or being sick, sexual problems, enlargement of the breasts (both in men and women), irregular menstrual periods, confusion and skin rash.

Who cannot take potassium-sparing diuretics?

There are very few people who are not able to take these medicines. They should not be taken by anyone who has high levels of potassium in their blood, severe kidney problems, or Addison's disease. In addition, potassium supplements should not be taken with these medicines. Some salt substitutes that you can buy are high in potassium. These should be avoided if you take a potassium-sparing diuretic.

How to use the Yellow Card Scheme

If you think you have had a side-effect to one of your medicines, you can report this on the Yellow Card Scheme. You can do this online at the following web address: www.mhra.gov.uk/yellowcard.

The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that your medicines may have caused. If you wish to report a side-effect, you will need to provide basic information about:

  • The side-effect.
  • The name of the medicine which you think caused it.
  • Information about the person who had the side-effect.
  • Your contact details as the reporter of the side-effect.

It is helpful if you have your medication and/or the leaflet that came with it with you while you fill out the report.