What are diuretics?

Diuretics are commonly called ‘water tablets’. They work by increasing urine output. There are several different types of diuretics and they are commonly given as tablets. Many, but not all people with PH are prescribed diuretics. Diuretics work by causing the kidneys to increase the amount of salt and sodium that is filtered out of the blood and into the urine. When these salts are filtered out of the blood by the kidneys, water is also drawn alongside (like a magnet). As diuretics remove fluid from the body, they are often used to treat conditions where excess fluid has been retained in the body (known by the medical term ‘oedema’). Removing water from the blood decreases the volume of fluid circulating through the blood vessels. This subsequently decreases the pressure within the blood vessels. Heart failure can cause fluid to build up around the lungs, causing shortness of breath. Diuretics are used to help the body remove this excess fluid and therefore relieve the symptoms of heart failure. By doing this, they make it easier for the heart to pump blood around the body. This is useful in heart failure where the pumping mechanism of the heart is less effective. As diuretics cause people to produce more urine, many people prefer to take them in the morning rather than before going to bed, as this reduces the likelihood of needing to get up in the
night to visit the toilet.

Common diuretics used are:

  • furosemide (previously called frusemide)
  • bumetanide
  • bendroflumethiazide
  • metolazone
  • spironolactone.
  • amiloride

How to take diuretics

Diuretics are taken to make patients produce more urine. For very practical reasons it is recommended that these are taken in the morning (for once daily dosing) with a second dose at lunchtime if prescribed. In exceptional circumstances, you can make minor adjustments to the time at which you take your diuretic. You could take it later in the day, to make it easier for you to deal with, eg car journeys or important appointments. If you have an appointment with a doctor or nurse on one of these days, you should tell them of this change. Otherwise they may think your diuretic is not working properly.

Side effects of diuretics

People taking diuretics should have regular blood tests to monitor their kidney function. Below is a list of possible side effects with diuretics. Don’t worry too much about the possibility of side effects. Just because a side effect is stated here, it doesn’t mean that you will experience it.

• Headache.
• Thirst.
• Disturbed sleep.
• A drop in blood pressure that occurs when going from lying down to sitting or standing, which results in dizziness and light-headedness.
• Fatigue.
• Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain.
• Dizziness.
• Loss of appetite.
• Changes in the levels of chemical components, electrolytes, in the blood (found by urine or blood tests).
• A general feeling of being unwell (malaise).
• Rash or itching.

Some people may experience fatigue when first taking diuretics, but this usually passes after they have been on the medication for some time. Any of the following symptoms should be reported to the doctor promptly. This is so that the amount of fluids and salts in your body can be checked: excessive thirst, lethargy, confusion, weakness, drowsiness, muscle cramps, lower than normal production of urine, feeling sick and vomiting.

If you do get side effects, you should discuss these with your PH specialist, nurse or GP. They may be able to suggest a different type of medicine.