Alendronic acid is a type of medicine called a bisphosphonate. It helps your bones stay as strong as possible.

It can help if you have or are at risk of getting a health problem called osteoporosis. This is where your bones get weaker and more likely to break.

Osteoporosis can happen for many reasons, but you're more likely to get it if you're a woman who has been through the menopause or if you take steroids, such as prednisolone, for a long time. Some types of cancer treatment can also increase your risk of getting osteoporosis.

Alendronic acid is only available on prescription. It comes as tablets, soluble tablets that dissolve in water to make a drink, or as a liquid that you drink.

• Alendronic acid is good for your bones - it makes them stronger and less likely to break.
• Most people take it as a weekly tablet or liquid.
• 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 doesn't 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 also known as alendronate sodium or alendronate. It is also called by the brand names Fosamax and Binosto. When mixed with colecalciferol (vitamin D3), it's called Fosavance.

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

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

• have had an allergic reaction to alendronic acid or any other medicine in the past
• have digestive problems, problems swallowing or any problems with your food pipe
• can't sit up or stand for at least 30 minutes
• 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 or breastfeeding, or trying to get pregnant

You'll usually take alendronic acid once a week, as a tablet. It also comes as a liquid or soluble tablet that you take once a week, or as a tablet you take once a day.

Follow your doctor's instructions about exactly how and when to take your medicine. If you're taking a weekly dose, you need to take your medicine on the same day each week, so choose a day that suits your routine.

How much will I take?

The usual dose for adults is 70mg taken once a week, or 10mg taken once a day.

How to take it

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

Take your medicine first thing in the morning, when you get up. 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 when your stomach is empty, so your body can absorb it properly. It's important to take alendronic acid while you're sitting up or standing. Stay upright for 30 minutes after taking your medicine - you can be sitting, standing or walking.

Tablets - swallow the tablet whole with a large glass of plain tap water (at least 200ml). Do not take it with mineral water. Do not chew, break, crush or suck the tablet.

Soluble tablets - dissolve a tablet in half a large glass of plain tap water (at least 120ml). Do not use mineral water. Wait until the fizzing has stopped and the tablet has completely dissolved. Drink your medicine, and then drink at least 30ml (2 tablespoons) of plain tap water. Do not swallow or chew the undissolved tablet. Do not let it dissolve in your mouth.

Liquid - each 70mg dose of liquid comes in its own bottle. Swallow the full dose in one go, then drink at least 30ml (2 tablespoons) of plain tap water. Don't worry if you spill any of the liquid by mistake - rinse it off and wash your hands.

If it's not safe to drink your tap water for whatever reason, you can boil the water and let it cool before drinking.

What if I forget to take it?

Once a day (10mg) - if you forget to take your daily dose, don't worry. Take your next dose on the following day, in the morning. Never take 2 doses at the same time to make up for a forgotten one.

Once a week (70mg) - if you forget to take your weekly dose on the usual day, don't worry. As soon as you remember, wait until the next day and then take your medicine first thing in the morning. Never take 2 doses to make up for a forgotten one. After this, go back to taking your weekly dose on your usual day.

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 to take your medicine.

What if I take too much?

If you take an extra 10mg or 70mg dose of alendronic acid by accident, it's unlikely to harm you. Immediately drink a full glass of milk and stay upright for at least 30 minutes. Do not make yourself vomit, as this may irritate your food pipe.

If your child takes an extra dose, get them to drink a full glass of milk immediately. Contact their doctor straight away. Keep your child sitting up or standing for at least 30 minutes. Do not make them vomit, as this may irritate their food pipe.

Speak to your pharmacist or doctor if you're worried, have any symptoms or take more than 1 extra dose of alendronic acid.

If you're taking a weekly 70mg dose, talk to your pharmacist or doctor if you accidentally take more than 1 extra dose in the same week.

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 the side effects bother you or don't 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. 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

Serious allergic reaction

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.

What to do about:

• constipation - eat more high-fibre foods such as fresh fruit, vegetables and cereals, and drink plenty of water. Try to exercise more regularly, by going for a daily walk or run for example. If this doesn't help, talk to your pharmacist or doctor. Watch this short video about how to treat constipation.
• diarrhoea- drink plenty of water, taking frequent small sips. 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 passes.
• headaches, muscle or joint pain - make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask your pharmacist to recommend a painkiller. 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. For swollen ankles, 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 and more frequent meals, eat and drink slowly, and exercise regularly. If the symptoms get worse, contact your doctor straight away.
• itching or a mild rash - it may help to take an antihistamine, which you can buy from a pharmacy. Check with the pharmacist to see what type is suitable for you.
• feeling sleepy or tired - do not drive, or use tools or machinery, if you're feeling tired. Do not drink any alcohol, as this will make you feel more tired.
• hair loss - thinning hair or mild hair loss isn't usually anything to worry about. Talk to your pharmacist or doctor if you're concerned. Some hair loss treatments are available.

Alendronic acid isn't usually recommended during pregnancy. This is because there hasn't been enough research into its safety.

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

Alendronic acid and breastfeeding

Although it's generally safe to take this medicine while breastfeeding, it may not be suitable in some cases. Check with your doctor about what's best for you and your baby.

When taking alendronic acid, it's really important not take any other medicines by mouth at the same time. Wait for at least 30 minutes before taking your other medicines - they can interfere with how well your body absorbs alendronic acid and stop it working properly.

There are some medicines that may interfere with 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 and thalidomide, or if you're having chemotherapy or taking steroids such as prednisolone and dexamethasone - these may increase the risk of damage to your jaw bone
• non-steroidal anti-inflammatories (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

Mixing alendronic acid with herbal remedies or supplements

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