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).

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


7. 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.

8. Pregnancy and breastfeeding

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.


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.

10. 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.

11. Common questions about alendronic acid

Related conditions

Page last reviewed: 10/09/2021
Next review due: 10/09/2024