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 pills' because they make you pee more. This helps get rid of extra fluid in your body.

Bendroflumethiazide is only available on prescription. It comes as tablets or as a liquid you swallow.

Key facts

  • It's usual to take bendroflumethiazide once a day.
  • Most people need to pee about 2 hours after taking bendroflumethiazide and then again within a few hours.
  • Do not take bendroflumethiazide after 4pm or you may have to wake up in the night to go to the toilet.
  • You may experience changes to your cholesterol levels or other fats (lipids). Your doctor will carry out regular blood tests to check this and will advise you what to do if there are any changes.
  • Bendroflumethiazide is also called by the brand names Aprinox and Neo-Naclex.
  • Bendroflumethiazide is not usually recommended during pregnancy or while breastfeeding.

Who can and can't take bendroflumethiazide

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

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

  • have had an allergic reaction to bendroflumethiazide or any other medicines in the past
  • 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
  • have 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

How and when to take it

How much to take

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

The usual 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 1 to 3 times a week

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 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.

Do not take bendroflumethiazide too late in the day (after 4pm) or at night, otherwise you may have to wake up to go to the toilet.

How to take it

You can take bendroflumethiazide with or without food.

Swallow the tablets whole with a drink of water.

If you're taking bendroflumethiazide as a liquid, make sure you shake the bottle well. It will come with a plastic spoon or syringe to help you measure the correct amount. If you don't have one, ask your pharmacist. Do not measure the liquid with a kitchen teaspoon, as it won't give the right amount.

What if I forget to take it?

Take your forgotten dose as soon as you remember, unless it is after 4pm. In this case, leave out 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?

Too much bendroflumethiazide can cause weak or fast heartbeats, fits (seizures), dizziness and confusion - these are signs of dehydration.

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

Go to emergency unit straight away if you take too much bendroflumethiazide and feel unwell

If you go to an emergency unit, 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.

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 can't 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 skin or whites of the eyes (jaundice), dark pee or pale poo - these could be signs of liver problems
  • are feeling 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 to bendroflumethiazide (anaphylaxis).

Call your local emergency service if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

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

How to cope with side effects

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. Speak to your doctor if your symptoms continue for more than a week.
  • 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. 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 - 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. Have nutritious snacks that are high in calories and protein, such as dried fruit and nuts.
  • constipation - eat more high-fibre foods such as fresh fruit, vegetables and cereals, and drink plenty of water. Try to exercise more regularly - for example, by going for a daily walk or run. If this doesn't help, talk to your pharmacist or doctor. Watch this short video  about how to treat constipation.
  • severe joint pain - if you get severe joint pain and the skin over the joint is red, hot and swollen, this could be a sign of gout. 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 get up more slowly. A drink of water may also help. Do not drive 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.

Pregnancy and breastfeeding

Bendroflumethiazide isn't normally recommended in pregnancy. However, your doctor may prescribe it if they think the benefits of the medicine outweigh the risks.

If you're trying to get pregnant or already are pregnant, talk to your doctor about the benefits and possible harms of taking bendroflumethiazide.

It will depend on how many weeks pregnant you are and why you're taking the medicine. There may be other treatments that are safer for you.

Bendroflumethiazide and breastfeeding

Bendroflumethiazide isn't normally recommended when breastfeeding. It can reduce the amount of breast milk you produce.

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

Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

Cautions with other medicines

Some medicines can interfere with the way bendroflumethiazide works.

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

  • non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen, or aspirin for pain relief
  • medicines to treat heart problems, including amiodarone, digoxin, disopyramide, flecainide and sotalol
  • medicines to treat sickness or nausea (antiemetics), such as domperidone, metoclopramide and prochlorperazine
  • antidepressants, such as amitriptyline, citalopram and venlafaxine
  • medicines for other mental health problems, such as chlorpromazine, pimozide, trifluoperazine and lithium
  • medicines that affect levels of salts (electrolytes) in your blood, including potassium, sodium, calcium and magnesium, corticosteroids or other diuretics
  • medicines used for asthma, including inhalers such as formoterol, salbutamol or salmeterol
  • allopurinol, a medicine to treat gout
  • ciclosporin, a medicine used to treat psoriasis or rheumatoid arthritis
  • insulin or any other medicine used to treat diabetes
  • carbamazepine, a medicine for epilepsy
  • calcium or vitamin D supplements, including alfacalcidol or calcitriol

Mixing bendroflumethiazide with herbal remedies and supplements

There's very little information about taking herbal remedies and supplements with bendroflumethiazide.


For safety, tell your pharmacist or doctor if you're taking any other medicines, including herbal remedies, vitamins or supplements.

Common questions