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Alendronic acid - Brand names: Fosamax, Binosto, alendronate sodium, alendronate

On this page

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

1. About alendronic acid

Alendronic acid is a type of medicine called a bisphosphonate. Bisphosponates are prescribed to help your bones stay as strong as possible. Taking alendronic acid can help if you have, or are at risk of developing, osteoporosis. This is a condition that causes your bones to get weaker and be more likely to break.

Osteoporosis can happen for many reasons, but you are more likely to get it if:

  • you're a woman who has been through the menopause
  • you take steroids, such as prednisolone, every day for a long time (which means 3 months, or longer)
  • you've had a certain type of cancer treatment – some treatments can increase your risk of developing osteoporosis. Your oncology doctor or nurse will discuss this with you

Talk to your doctor if you are worried about the health of your bones because of the medicines you take, or changes to your hormone levels because of the menopause.

Alendronic acid is only available on prescription. You can take it as a standard tablet, a soluble tablet that dissolves in water, or as a liquid that you drink.

2. Key facts

  • Alendronic acid is good for your bones – it makes them stronger and less likely to break.
  • You'll usually take it as a tablet or liquid, once a week.
  • Take alendronic acid first thing in the morning, before you have anything to eat or drink and before you take any other medicines. Stay sitting or standing for 30 minutes so the medicine does not irritate your food pipe (oesophagus).
  • It's important to look after your teeth and have regular dental check-ups while taking alendronic acid because it can sometimes damage the jaw bone, but this is rare.
  • Alendronic acid is known as Fosavance when it's mixed with colecalciferol (vitamin D3)

3. Who can and cannot take alendronic acid

Alendronic acid can be taken by most adults aged 18 and over. It's sometimes prescribed for children with osteoporosis.

Do not give it to children under the age of 18 unless it's prescribed by a doctor.

Alendronic acid is not suitable for some people. To make sure it's safe for you, tell your doctor if you:

  • have ever had an allergic reaction to alendronic acid or any other medicine
  • have problems digesting food, swallowing or other problems with your food pipe (oesophagus)
  • have taken alendronic acid before but it made you feel dizzy and unable to stand or sit upright for at least 30 minutes after taking it
  • have low calcium levels in your blood – alendronic acid sometimes causes low blood calcium, so your calcium levels could become even lower
  • have kidney problems
  • have cancer, or are having chemotherapy or radiotherapy
  • have problems with your teeth, or are waiting for dental treatment such as having a tooth out
  • smoke, or used to smoke – this may increase your risk of dental problems
  • are pregnant, trying to get pregnant or breastfeeding

4. How and when to take alendronic acid

Follow your doctor's instructions about how and when to take your medicine.

Dosage and strength

The usual dose of alendronic acid for adults is 70mg taken once a week. There is also a 10mg tablet you take once a day.

You will usually take alendronic acid once a week:

  • as a standard tablet
  • as a liquid that you drink
  • as a tablet that dissolves in water (dispersible)

Whether you take alendronic acid daily or weekly, you need to take your medicine at the same time each day or day of the week. If it's weekly, choose a day that suits your routine.

How to take alendronic acid

It's important to follow the instructions for this medicine very carefully. If you do not, it may not work or it could irritate and damage your food pipe as you swallow it.

The best time to take your medicine is usually 30 minutes before you have breakfast. Take it on an empty stomach, before you have anything to eat or drink (other than plain tap water) and before you take any other medicines that you swallow.

Alendronic acid works best on an empty stomach because your body can absorb it properly.

It's important to take alendronic acid while you're sitting up or standing. Try to stay upright for 30 minutes after taking your medicine – you can be sitting, standing or walking.

5. Side effects

Like all medicines, alendronic acid can cause side effects in some people, but many people have no side effects, or only minor ones.

Common side effects

These common side effects happen in more than 1 in 100 people. Talk to your doctor or pharmacist if they bother you or do not go away:

  • constipation
  • diarrhoea
  • feeling dizzy (or signs of vertigo)
  • headaches, muscle or joint pain
  • swollen joints, hands or legs
  • indigestion, bloating or wind
  • itching or a mild rash
  • feeling sleepy or tired
  • hair loss

Serious side effects

Some people may have serious side effects when taking alendronic acid. These include heartburn (or heartburn that gets worse), problems or pain when swallowing, or chest pain. These may be signs of ulcers in your food pipe (oesophagus). If this happens, stop taking alendronic acid and speak to a doctor.

Other serious side effects are rare, but call a doctor straight away if you have:

  • a loose tooth, mouth sores, or swelling or pain in your mouth or jaw – contact your dentist as well as your doctor, as this could be a sign of damage to your jaw bone
  • pain, weakness or discomfort in your thigh, hip or groin – this happens rarely but may be an early sign of a broken thigh bone
  • severe pain in your joints, muscles or bones
  • ear pain, discharge from your ear or an ear infection – these can be signs of damage to the bones in your inner ear
  • black or red poo – these can be signs of an ulcer or bleeding from your gut
  • blurred vision, painful or red eyes – these can be signs of swelling of the eye
  • muscle cramps or spasms, a tingling sensation in your fingers or around your mouth – these can be symptoms of low calcium levels in your blood

In rare cases, alendronic acid may cause a serious allergic reaction (anaphylaxis).

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 alendronic acid. 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 alendronic acid

What to do about:

  • constipationeat more high-fibre foods such as fresh fruit, vegetables and cereals, and drink plenty of water. Try to increase your level of exercise if you can, by going for a daily walk or run. If this does not help, talk to your pharmacist or doctor. This short video explains more about how to treat constipation.
  • diarrhoea – drink plenty of water. Speak to a pharmacist if you have signs of dehydration, such as peeing less than usual or having dark, strong-smelling pee. Do not take any medicines to treat diarrhoea without speaking to a pharmacist or doctor.
  • feeling dizzy – stop what you're doing, and sit or lie down until you feel better. Do not drive or use tools or machinery until your dizziness has gone.
  • headaches, muscle or joint pain – make sure you rest and drink plenty of fluids. Try not to drink too much alcohol. Ask your pharmacist to recommend a painkiller, and talk to your doctor if the pain lasts longer than a week or is severe.
  • swollen joints, hands or legs – try to rest. Avoid standing for long periods if you have swollen legs, and put your feet on a stool or cushion to raise your legs when you're sitting. Talk to your doctor if the swelling is severe or lasts longer than a week.
  • indigestion, bloating or wind – make sure you follow the directions for taking alendronic acid carefully and remain upright for at least 30 minutes after taking it. It might help to eat smaller meals more often. You could also try eating and drinking more slowly, and increase your level of exercise if you can. If the symptoms get worse, contact your doctor straight away.
  • itching or a mild rash – it may help to take an antihistamine , which can reduce these symptoms. You can buy antihistamines from a pharmacy but check with the pharmacist to see what type is suitable for you when taking this medicine.
  • feeling sleepy or tired – do not drive, cycle or use tools or machinery, if you're feeling tired. Try not to drink any alcohol, as this will make you feel more tired.
  • hair loss – thinning hair or mild hair loss in itself can be stressful but it is not usually a sign of anything to worry about. Talk to your pharmacist or doctor if you're concerned. Some hair loss treatments are available.

7. Pregnancy and breastfeeding

Alendronic acid and pregnancy

Alendronic acid is not recommended during pregnancy. This is because there has not been enough research into its safety.

Alendronic acid and breastfeeding

It's generally OK to take alendronic acid while breastfeeding. This is because we only expect very small amounts to pass into breast milk. It may not be suitable in a very small number of cases. Check with your doctor about what's best for you and your baby.

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

  • trying to get pregnant
  • pregnant
  • breastfeeding

For more information about how alendronic acid can affect you and your baby during pregnancy, find out more on the Best Use of Medicines in Pregnancy (BUMPS) website.

8. Cautions with other medicines

If you've been prescribed alendronic acid, do not take other medicines that you have to take by mouth (orally) at the same time. This is because it enters the stomach, soaks up the alendronic acid and stops it working properly.

If you do need to take another medicine by mouth, wait for at least 30 minutes.

Some medicines can affect the way alendronic acid works.

Tell your doctor if you're taking:

  • supplements or multivitamins containing calcium, iron, magnesium or zinc
  • antacids to relieve indigestion or heartburn
  • laxatives containing magnesium
  • cancer medicines such as bevacizumab or thalidomide
  • steroids such as prednisolone or dexamethasone – these may increase the risk of damage to your jaw bone
  • non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, which can increase the risk of irritating your food pipe, stomach or gut. Taking low-dose aspirin is OK
  • antibiotics such as gentamicin, amikacin or tobramycin – these can lower the calcium in your blood
  • deferasirox, a medicine used to remove excess iron from the body – this may increase the risk of bleeding from your gut

Also tell your doctor if you are having chemotherapy.

Mixing alendronic acid with herbal remedies or supplements

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

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 alendronic acid

How does alendronic acid work?

Alendronic acid increases the amount of calcium in your bones (your bone mineral density). This makes your bones stronger and less likely to break.

How long does it take to work?

Alendronic acid usually starts to work after 1 month. However, it may take 6 to 12 months for the medicine to fully protect your bones.

How good is it at preventing further broken bones?

If you have osteoporosis, or you've recently broken a bone, you're at risk of future breaks (fractures). However, you can significantly reduce the chance of this happening by taking alendronic acid.

If you're a woman in this "at risk" group, taking alendronic acid for at least 12 months can halve your chances of going on to fracture your wrist, hip or spine.

How long will I take it for?

You'll usually take alendronic acid long term, for at least 3 to 5 years. Your doctor will then review your ongoing need for it.

If you're having long-term treatment with steroids, you'll usually take alendronic acid until your steroid treatment stops. Your doctor will then review whether you need to carry on.

For other health problems, such as arthritis and diabetes, your doctor will usually assess your risk of broken bones every 3 to 5 years. This may include tests to check the strength (density) of your bones.

Depending on the results, you'll either keep taking alendronic acid, take a break from it or stop taking it completely.

How long do the effects last after I stop taking it?

Once you stop taking alendronic acid, the effects of the medicine will gradually wear off. Your bones may continue to benefit for up to 5 years afterwards.

The longer you take the medicine, the longer the effects will last.

Is it safe to take long term?

Alendronic acid is generally prescribed for a long time. While you're taking it, you're less likely to break a bone.

In a very small number of people, taking alendronic acid for more than 2 years can increase their chances of getting a rare type of bone damage in their inner ear and certain types of breaks to their thigh bones.

For this reason, your doctor will look at the benefits and risks of your treatment after 3 to 5 years and decide whether you should keep taking alendronic acid. This may involve some tests to check the strength (density) of your bones.

The benefits of taking alendronic acid generally outweigh the risks. If you're concerned or have any questions, talk to your doctor or pharmacist.

What happens if I do not take it?

Missing the odd dose probably will not affect the health of your bones. But if you keep forgetting to take your alendronic acid, or you do not want to take it, for whatever reason, then speak to your doctor. There are other treatments that can help your bones.

Any medicine can have side effects, but the benefits of alendronic acid usually far outweigh the risks.

By not taking it, you're more likely to break a bone. Broken bones are painful and can have serious consequences. In older people, for example, a broken hip can mean a loss of mobility for some time, although there is every chance of full recovery.

What can I do to keep my teeth healthy while taking it?

It's important to take good care of your teeth while you're taking alendronic acid, because it might affect your jaw bone.

It's a good idea to:

  • keep your teeth clean and have a dental check-up every 6 months. Your doctor may also recommend a dental check-up before your treatment starts
  • contact your doctor or dentist if you have any problems with your mouth or teeth, such as pain, swelling or loose teeth
What happens if I need dental treatment?

If you're having dental implants or having a tooth out while taking alendronic acid, there's a very small chance of damage to your jaw bone.

For safety, tell your dentist that you're taking alendronic acid. They may recommend a different type of dental treatment.

Will taking alendronic acid affect my arthritis?

Some types of arthritis and arthritis medicines can increase your risk of developing osteoporosis. Taking alendronic acid reduces this risk.

If you have arthritis and your doctor prescribes alendronic acid, let them know if the pain or swelling in your joints gets worse when you start taking this medicine.

Will it affect my fertility?

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

However, if you're trying to get pregnant, speak to a pharmacist or your doctor before taking alendronic acid. This is because most women will need to stop taking alendronic acid before getting pregnant.

Will it affect my contraception?

Alendronic acid does not affect any type of contraception including the contraceptive pill or emergency contraception.

Can I drive or ride a bike?

Alendronic acid may make you feel dizzy. It can also cause blurred vision, and bone, muscle or joint pain.

If this happens to you, do not drive, cycle or use any machinery or tools until the effects have worn off.

It's an offence to drive a car if your ability to drive safely is affected. It's your responsibility to decide if it's safe to drive. If you're in any doubt, do not drive.

Talk to your doctor or pharmacist if you're unsure whether it's safe for you to drive while taking alendronic acid. GOV.UK has more information on the law on drugs and driving.

Is there any food or drink I need to avoid?

Do not have anything to eat or drink before you take your alendronic acid first thing in the morning. You can drink tap water but this medicine must be taken on an empty stomach.

Take your alendronic acid first thing in the morning, on an empty stomach. Do not have anything to eat or drink beforehand, other than plain tap water. It's important to follow the instructions carefully (the how and when to take this medicine section has more detail), so that your medicine works properly.

Do not take your medicine with mineral water. If it's not safe to drink your tap water for any reason, you can boil it and let it cool before drinking it.

After taking your medicine, wait for 30 minutes. You can then eat and drink normally.

Can I drink alcohol with it?

Yes, you can drink alcohol while taking alendronic acid. However, drinking a lot of alcohol affects the strength of your bones and can increase your risk of breaks (fractures).

Can lifestyle changes help?

You can help keep your bones healthy by making some key lifestyle changes.

  • Eat food for strong bones – include some foods high in calcium and vitamin D.
  • Get vitamin D from sunlight – spend some time in the sun (wearing adequate sun protection).
  • Stop smoking – smoking harms your bones.
  • Cut down on alcohol – try not to drink more than 14 units of alcohol a week.
  • Exercise more – walking and low-impact aerobics are good for your bones. So are strength-training exercises where you use your own body weight.

Related conditions

Page last reviewed: 10 September 2021
Next review due: 10 September 2024