Bendroflumethiazide


1. About bendroflumethiazide

Bendroflumethiazide is a type of medicine called a diuretic. It's used to treat high blood pressure (hypertension) and the build-up of fluid in your body (oedema).

Diuretics are sometimes called "water tablets" because they make you pee more. This helps get rid of extra fluid in your body.

Bendroflumethiazide is only available on prescription. It usually comes as tablets. It can also come as a liquid you swallow, but this has to be specially ordered.


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  • You'll usually take bendroflumethiazide once a day in the morning.
  • If you take bendroflumethiazide later in the day you may have to wake up in the night to go to the toilet.
  • Common side effects include: needing to pee more often, mild stomach upset, dehydration, and low or high levels of salts (electrolytes) such as potassium or sodium in your blood.
  • Speak to your doctor or a pharmacist if you have diarrhoea or vomiting from a stomach bug or other illness. You may need to stop taking bendroflumethiazide for a short time.
  • Bendroflumethiazide is not usually recommended during pregnancy or while breastfeeding.

3. Who can and cannot take bendroflumethiazide

Bendroflumethiazide can be taken by most adults and children, including babies.

Bendroflumethiazide is not suitable for everyone. To make sure it is safe for you, tell your doctor if you:

  • have ever had an allergic reaction to bendroflumethiazide or any other medicine
  • have underactive adrenal glands (Addison's disease)
  • have low levels of sodium, potassium or magnesium in your blood
  • have high levels of calcium or uric acid in your blood
  • have liver problems
  • have kidney problems or difficulty peeing
  • are being sick (vomiting) or have diarrhoea
  • have diabetes
  • have gout
  • have a rare blood disease called porphyria
  • have an inflammatory condition called lupus
  • are pregnant, trying to get pregnant or breastfeeding

4. How and when to take bendroflumethiazide

Your dose will depend on what you are taking bendroflumethiazide for, your age and how well your kidneys work.

The usual adult dose for:

  • high blood pressure is 2.5mg once a day
  • build-up of fluid is 5mg to 10mg once a day – this may be reduced to a single dose taken 1 to 3 times a week

Occasionally, your doctor might prescribe bendroflumethiazide to be taken twice a day.

Your dose may be lower if you are over 65 or have kidney problems.

For babies and children, your doctor will use your child's weight or age to work out the right dose.

When to take it

It's usual to take bendroflumethiazide once a day, in the morning. If you take it later in the day you may have to wake up in the night to go to the toilet.

If your doctor prescribes it twice a day, take it once in the morning and again around midday.

It's best to take bendroflumethiazide at the same time every day to keep it working properly.

Sometimes your doctor may advise you to take bendroflumethiazide less often. You may only need to take it 2 or 3 times a week, in which case take it on the same days each week.

How to take it

You can take bendroflumethiazide with or without food.

Swallow the tablets whole with a drink of water. Speak to a pharmacist if you or your child finds it difficult to swallow tablets.

If you're taking bendroflumethiazide as a liquid, make sure you shake the bottle well. Use a plastic medicine spoon or oral syringe to help you measure each dose. If you do not have one, ask your pharmacist. Do not measure the liquid with a kitchen teaspoon, as it will not give the right amount.

What if I forget to take it?

If you forget to take bendroflumethiazide, take your forgotten dose as soon as you remember. However, if you normally take your dose in the morning and you do not remember before late afternoon, skip the missed dose and take your next dose at the usual time.

Do not take a double dose to make up for a forgotten dose.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember your medicines.

What if I take too much?

Taking more than your prescribed dose of bendroflumethiazide can cause weak or fast heartbeats, seizures or fits (body jerking and shaking uncontrollably), dizziness and confusion – these are signs of dehydration.

The amount of bendroflumethiazide that can lead to an overdose varies from person to person.

If you go to A&E, do not drive yourself. Get someone else to drive you or call for an ambulance.

Take the bendroflumethaizide packet, or the leaflet inside it, plus any remaining medicine with you.


5. Side effects

Like all medicines, bendroflumethiazide can cause side effects, although not everyone gets them.

You are less likely to get side effects if you are on a low dose, such as 2.5mg daily.

Side effects often get better as your body gets used to the medicine.

Common side effects

Common side effects of bendroflumethiazide include:

  • feeling thirsty, with a dry mouth
  • feeling or being sick (nausea or vomiting)
  • stomach pain
  • diarrhoea
  • loss of appetite
  • constipation
  • severe joint pain
  • feeling dizzy and faint
  • unexpected weight loss, frequent thrush, bladder or skin infections, tiredness, blurred vision and increased thirst

Serious side effects

It happens rarely, but some people have a serious side effect after taking bendroflumethiazide.

Call your doctor straight away if you:

  • have any bruises or bleeding (including nosebleeds) that you cannot explain – these could be a sign of blood problems
  • have severe and sudden stomach pain – this could be a sign of pancreas problems
  • have itching, yellowing of the whites of your eyes, yellowing of your skin (this may be less obvious on brown or black skin), dark pee or pale poo – these could be signs of liver problems
  • are feeling very thirsty, have dark yellow and strong-smelling pee, are feeling dizzy or lightheaded, or are peeing fewer than 4 times a day – you could be at risk of dehydration

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to bendroflumethiazide.

These are not all the side effects of bendroflumethiazide. For a full list, see the leaflet inside your medicine packet.


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7. How to cope with side effects of bendroflumethiazide

What to do about:

  • feeling thirsty with a dry mouth – it's important not to get dehydrated, but how much you drink will depend on why you're taking bendroflumethiazide. Check with your doctor how much water you can drink while you're taking this medicine.
  • feeling or being sick (vomiting) – stick to simple meals and do not eat rich or spicy food. If you're being sick, try frequent small sips of water to avoid dehydration. Speak to your doctor if your symptoms continue for more than a week, if you are vomiting frequently or if you are not able to drink water and may be at risk of dehydration.
  • stomach pain – try to rest and relax. It can help to eat and drink slowly, and have smaller, more frequent meals. Putting a heat pad or covered hot water bottle on your stomach may also help. If you are in a lot of pain, speak to your pharmacist or doctor.
  • diarrhoea – drink plenty of water or other fluids. However, check with your doctor how much water you can drink while you're taking bendroflumethiazide. Speak to a pharmacist if you are peeing less than usual or have dark yellow and strong-smelling pee, as you could be at risk of dehydration. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
  • loss of appetite – eat when you would usually expect to be hungry. If it helps, eat smaller meals but more often than usual. Snack when you're hungry and choose nutritious snacks that are high in calories and protein, such as dried fruit and nuts.
  • constipationget more fibre into your diet by eating fresh fruit, vegetables and cereals, and drink plenty of water. However, check with your doctor how much water you can drink while you're taking bendroflumethiazide. Try to exercise more regularly, for example, by going for a daily walk or run. If this does not help, talk to your pharmacist or doctor. You may also want to watch this short video on how to treat constipation.
  • severe joint pain – if you get severe joint pain and the skin over the joint is hot, swollen and red, this could be a sign of gout. The redness may be less noticeable on brown or black skin. Speak to your doctor if you have these symptoms.
  • feeling dizzy and faint – these could be signs of low blood pressure. If you feel dizzy or faint, stop what you're doing. Try sitting or lying down until the symptoms pass, and then get up slowly. A drink of water may also help. Do not drive, ride a bike or operate machinery if you are affected. Speak to your doctor if this keeps happening.
  • unexpected weight loss, frequent thrush, bladder or skin infections, tiredness, blurred vision and increased thirst – speak to your doctor, as these could be signs of high blood sugar or another condition, and your doctor might want to run some tests.

8. Pregnancy and breastfeeding

Bendroflumethiazide is not normally used during pregnancy. There are other medicines that are more suitable for treating high blood pressure in pregnancy.

If you're trying to get pregnant or are already pregnant, talk to your doctor about whether taking bendroflumethiazide is right for you. It's likely that you will be switched to a different medicine for high blood pressure.

Bendroflumethiazide and breastfeeding

Bendroflumethiazide is not normally recommended when breastfeeding. It is not expected to cause any harm to your baby, but it can reduce the amount of breast milk you produce.

If you need to take bendroflumethiazide while you're breastfeeding your doctor or midwife will monitor your baby's weight.

Talk to your doctor, as other medicines might be better while you're breastfeeding.


9. Cautions with other medicines

Some medicines can affect the way bendroflumethiazide works.

Tell your doctor if you're taking any of these medicines before starting bendroflumethiazide:

  • lithium, a medicine used to treat depression and bipolar disorder
  • allopurinol, a medicine to treat gout
  • non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen, or aspirin for pain relief
  • insulin or any other medicine used to treat diabetes
  • ciclosporin, a medicine used for preventing transplant rejection or to treat other medical conditions such as psoriasis or rheumatoid arthritis

Also tell your doctor if you're taking medicines that can affect your heart rhythm. There are lots of these, so check with your doctor or pharmacist. Examples include:

Tell your doctor if you're taking medicines that affect levels of potassium, sodium, calcium and magnesium and other salts or electrolytes in your blood. There are lots of these, so check with your doctor or pharmacist. Examples include:

Mixing bendroflumethiazide with herbal remedies and supplements

There's very little information about taking herbal remedies and supplements with bendroflumethiazide. They are not tested in the same way as pharmacy and prescription medicines.


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Page last reviewed: 27/07/2021
Next review due: 27/07/2024