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

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 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.

2. 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.

3. Who can and cannot 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

4. How and when to take it


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.

Urgent advice: Go to A&E straight away if:

  • you take too much bendroflumethiazide and feel unwell

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 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 .

Immediate action required: Call 999 or go to A&E now 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.


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

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.

7. 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.

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

  • trying to get pregnant
  • pregnant
  • breastfeeding

8. 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:

Mixing bendroflumethiazide with herbal remedies and supplements

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

Important: Medicine safety

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

9. Common questions

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 the body (oedema). You will also have less fluid in your blood, which helps reduce blood pressure.

How long does bendroflumethiazide take to work?

Bendroflumethiazide takes around 2 hours to start working. It takes 3 to 6 hours for your body to produce increased amounts of pee.

How long does it work for?

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

How long will I take it for?

Depending on the reason you're taking bendroflumethiazide, you may have to take it for a long time - perhaps even for the rest of your life.

Is it safe to take for a long time?

Bendroflumethiazide is safe to take for a long time, but you will have to see your doctor or nurse every so often for blood and urine tests. This is to make sure the chemicals 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 come off it?

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

It's usually best to drink normally while you're taking bendroflumethiazide. A good rule is to drink enough fluid so that you're not thirsty for long periods.

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.

However, if you have heart failure or kidney problems, you might need to limit how much fluid you drink. In this case, your doctor or nurse will tell you exactly how much you need to drink each day.

Are there other treatments that could help?

There are other water tablets (diuretics), including other thiazides, that can help treat high blood pressure or a build-up of fluid.

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

Does it affect asthma?

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 ill?

If you get diarrhoea or vomiting from a stomach bug or other illness, tell your doctor or speak to a pharmacist. You may need to stop taking bendroflumethiazide for a short time until you can eat and drink normally again.

Can I take bendroflumethiazide before surgery?

Tell your doctor that you're taking bendroflumethiazide if you're going to be asleep under a general anaesthetic for an operation, or if you're going to have a major operation - such as a caesarean section - without 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 firm evidence to suggest that taking bendroflumethiazide will reduce fertility in either men or women. In rare cases, bendroflumethiazide can cause erectile dysfunction (impotence) in men.

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 before taking bendroflumethiazide.

Will it affect my contraception?

Bendroflumethiazide won't affect any type of contraception.

However, some types of hormonal contraception, like the combined pill and contraceptive patch, aren't 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 can alter your blood pressure and make you feel dizzy or lightheaded.

During the first few days of taking bendroflumethiazide or after increasing the dose, 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 while you're taking bendroflumethiazide. It may raise your blood pressure, make you feel dizzy and cause dehydration.

Is there any food or drink I need to avoid?

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

Caffeinated drinks - such as tea, coffee, cola and energy drinks - are not recommended. They can increase the effects of bendroflumethiazide, making 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 - plus the health of your heart - by making some key lifestyle changes. These will also help if you have high blood pressure or heart failure.

  • Quit smoking - smoking increases your heart rate and blood pressure. Quitting smoking brings down your blood pressure and relieves heart failure symptoms. Try to avoid secondhand smoke too.
  • Cut down on alcohol - drinking too much alcohol raises blood pressure over time and makes heart failure worse. 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 doesn't need to be too energetic - walking every day can help.
  • Eat well - aim to eat a diet that includes plenty of fruit and veg, wholegrains, fat-free or low-fat dairy products, and lean proteins. It's a good idea to cut down on salt too. Eating too much salt is the biggest cause of high blood pressure - the more you eat, the higher your blood pressure will be. Aim for no more than 6g of salt a day.
  • Deal with stress - when you're anxious or upset, your heart beats faster, you breathe more heavily and your blood pressure often goes up. This can make heart failure worse too. Find ways to reduce stress in your life. To give your heart a rest, 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 heart failure, it's recommended that you have a flu jab every year and a pneumonia vaccination (also called the pneumococcal vaccine) every 5 years. Ask your doctor about these vaccinations. You can have them free on the NHS if you have heart failure.

If you have oedema, you can also try:

  • raising your legs 3 to 4 times a day to improve your circulation
  • avoiding standing for long periods of time