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Bendroflumethiazide - Brand names: Aprinox, Neo-Naclex

On this page

  1. About bendroflumethiazide
  2. Key facts
  3. Who can and cannot take bendroflumethiazide
  4. How and when to take bendroflumethiazide
  5. Side effects
  6. How to cope with side effects of bendroflumethiazide
  7. Pregnancy and breastfeeding
  8. Cautions with other medicines
  9. Common questions about 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.

2. Key facts

  • 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.

Urgent advice: Contact 111 for advice now if:

  • you or your child have taken too much bendroflumethiazide

Go to or call 111.

If you need advice for a child under 5 years, call 111.

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.

Immediate action required: Call 999 now if:
  • your lips, mouth, throat or tongue suddenly become swollen
  • you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
  • your throat feels tight or you're struggling to swallow
  • your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
  • you suddenly become very confused, drowsy or dizzy
  • someone faints and cannot be woken up
  • a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)

You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.

These can be signs of 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.


You can report any suspected side effect using the Yellow Card safety scheme.

Visit Yellow Card for further information.

6. 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.

7. Pregnancy and breastfeeding

Bendroflumethiazide and pregnancy

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.

Non-urgent advice: Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

8. 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.

Important: Medicine safety

Tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements.

9. Common questions about bendroflumethiazide

How does bendroflumethiazide work?

Bendroflumethiazide is a type of medicine called a thiazide diuretic.

A thiazide diuretic makes your body get rid of extra fluid through your kidneys. It increases the amount of salts (such as sodium and potassium) and water you pee out.

This means you have less fluid in your tissues, which helps get rid of swelling and a build-up of fluid in your body (oedema). You will also have less fluid in your blood vessels, which helps reduce your blood pressure.

How long does bendroflumethiazide take to work?

Bendroflumethiazide takes around 2 hours to start working. When you first start taking bendroflumethiazide it may take 3 or 4 days for your blood pressure to come down.

How long does it work for?

A dose of bendroflumethiazide works for about 12 to 24 hours.

You need to keep taking bendroflumethiazide regularly at the dose recommended by your doctor for it to continue to work.

How long will I take it for?

For high blood pressure you will probably need to take bendroflumethiazide for a long time, maybe even for the rest of your life.

For fluid build-up it will depend on what's causing it, so check with your doctor how long you will need to take bendroflumethiazide for.

Is it safe to take for a long time?

Bendroflumethiazide is safe to take for a long time if it's needed.

Check with your doctor how long you will need to take bendroflumethiazide for, and make sure you see your doctor or nurse regularly to check your blood pressure and for blood tests. This is to make sure your kidneys are working well and the salts (electrolytes) in your blood are properly balanced.

How often you'll need these tests will depend on the reason you're taking bendroflumethiazide, if your dose has changed recently or if you have any other health problems.

What will happen if I stop taking it?

If you stop taking bendroflumethiazide, your blood pressure is likely to rise. If you're taking it for a build-up of fluid (oedema), you may find extra fluid starts to become a problem again.

The levels of salts (electrolytes) in your blood might also change. Your doctor may suggest having a blood test after a week or two to check this.

How much fluid should I drink while I'm taking bendroflumethiazide?

Unless you have been advised by a doctor or nurse to limit how much fluid you drink, it's usually best to drink normally while you're taking bendroflumethiazide.

A good rule is to drink enough so that you're not thirsty for long periods.

Speak to a doctor if you're feeling unwell and not able to drink properly.

Steadily increase the amount you drink when you're exercising and during hot weather. If your pee's pale yellow or clear, then you're probably drinking enough fluid.

Are there other treatments that could help?

There are other diuretics, including other thiazide diuretics, that can help treat high blood pressure or a build-up of fluid.

Examples of other thiazide diuretics include indapamide, chlortalidone, hydrochlorothiazide and metolazone. Examples of other types of diuretics include furosemide, bumetanide, amiloride and spironolactone.

There are also lots of other types of medicines to lower your blood pressure. They work in a different way to diuretics and include:

If you have high blood pressure, you'll often need to take more than one medicine to get the best effect.

If you cannot take bendroflumethiazide because of side effects, you may be able to switch to another medicine. Your doctor will advise which blood pressure medicines are best for you depending on your age, ethnicity and health.

Does it affect asthma or asthma medicines?

Bendroflumethiazide does not make asthma worse.

However, some medicines used to treat asthma can cause low levels of potassium in your blood, and this is also a side effect of bendroflumethiazide.

Speak to your doctor if you have asthma and have questions about whether bendroflumethiazide is safe for you.

Is it safe to take bendroflumethiazide when I'm vomiting or have diarrhoea?

If you get diarrhoea or vomiting, from a stomach bug or other illness, or you're not able to eat or drink properly, tell your doctor or speak to a pharmacist.

You may need to stop taking bendroflumethiazide for a short time. This is because taking bendroflumethiazide can increase the risk of acute kidney injury, which is damage to your kidneys that can happen suddenly if you are not able to eat or drink properly or if you lose too much fluid due to diarrhoea or vomiting.

Can I take bendroflumethiazide before surgery?

Tell your doctor that you're taking bendroflumethiazide if you're going to have a general anaesthetic.

Bendroflumethiazide can reduce your blood pressure when it's used with a general anaesthetic.

Your doctor may advise you to stop taking bendroflumethiazide 24 hours before surgery.

Will it affect my fertility?

There's no evidence to suggest that taking bendroflumethiazide will reduce fertility in either men or women.

However in rare cases, bendroflumethiazide can cause erectile dysfunction (impotence).

Speak to your doctor if you're having problems getting or keeping an erection. If bendroflumethiazide is the cause, it usually gets better within a few weeks of stopping treatment.

If you're trying to get pregnant, speak to a pharmacist or your doctor. Bendroflumethiazide is not generally recommended during pregnancy so your doctor may advise switching to a different medicine.

Will it affect my contraception?

Bendroflumethiazide will not affect any type of contraception including emergency contraception.

However, some types of hormonal contraception, like the combined pill and contraceptive patch or vaginal ring, are not usually recommended for women with high blood pressure. Talk to your doctor if you're taking a hormonal contraceptive.

Can I drive or ride a bike?

Bendroflumethiazide can make you feel dizzy. If this happens to you, do not drive a car, ride a bike, or use tools or machinery until you feel better.

Can I drink alcohol with it?

Drinking alcohol with bendroflumethiazide can lower your blood pressure or cause dehydration and make you feel dizzy or lightheaded.

During the first few days of taking bendroflumethiazide, or after increasing your dose, wait to see how the medicine affects you before you drink any alcohol.

If you feel OK, you can drink alcohol in moderation by following the national guidelines of no more than 14 units a week for men and women. A standard glass of wine (175ml) is 2 units. A pint of lager or beer is usually 2 to 3 units of alcohol.

If you have high blood pressure it's best not to drink alcohol in large amounts regularly as this can raise your blood pressure further.

Is there any food or drink I need to avoid?

Low-salt (or low-sodium) diets are not recommended when taking this medicine. This is because bendroflumethiazide can cause low levels of salts (or electrolytes) in your body.

Caffeinated drinks, such as tea, coffee, hot chocolate, cola and energy drinks, are not recommended. They can increase the effects of bendroflumethiazide, and make you need to pee more.

You can reduce the amount of caffeine you're having by swapping to decaffeinated drinks and drinking plenty of other fluids, such as water or squash.

Can lifestyle changes help?

You can boost your general health and the health of your heart by making some key lifestyle changes. These will also help if you have high blood pressure.

  • Lose weight if you're overweight.
  • Quit smoking – smoking increases your heart rate and blood pressure. Quitting smoking brings down your blood pressure and reduces your risk or heart disease and stroke. Try to avoid secondhand smoke too.
  • Limit your alcohol units – drinking too much alcohol raises blood pressure over time. If you have high blood pressure, you should avoid drinking large amounts of alcohol regularly, as it can raise your blood pressure.
  • Exercise – regular exercise lowers blood pressure by keeping your heart and blood vessels in good condition. It does not need to be too energetic, walking every day can help.
  • Eat well – aim to eat a diet that includes plenty of fruit and vegetables, wholegrains, fat-free or low-fat dairy products, and lean proteins. It's a good idea to follow these tips for a lower salt diet too. Eating too much salt is the biggest cause of high blood pressure. The more salt you eat, the higher your blood pressure will be. Aim for no more than 6g of salt a day, but avoid very strict low salt or low sodium diets while you are taking bendroflumethiazide.
  • Deal with stress – when you're anxious or upset, your heart beats faster, you breathe more heavily and your blood pressure often goes up. Find ways to reduce stress in your life. Try napping or putting your feet up when possible. Spend time with friends and family to be social and help avoid stress.
  • Vaccinations – if you have a serious long-term health condition such as being very overweight, coronary heart disease, heart failure, diabetes, liver disease or chronic kidney disease, it's recommended that you have the flu vaccine every year and the pneumococcal vaccine as recommended by your GP. Ask your doctor about these vaccinations. You can have them free on the NHS if you are eligible.

If you have oedema, you can also try:

  • lying down and raising your legs using a pillow 3 to 4 times a day to improve your circulation
  • taking gentle exercise, such as walking
  • avoiding standing for long periods of time