Bifosfonatos

What are bisphosphonates?

Examples of conditions which bisphosphonates can help treat are:

• Osteoporose - a condition where bones become thin and more prone to fracture.

• Doença de Paget do osso.

• Cancer that has spread to the bones (bone metastases from cancers such as breast cancer).

• Very high amounts of calcium in the blood in people who are very ill with advanced cancer.

The rest of this leaflet is only about bisphosphonates for osteoporosis that your doctor may prescribe in order to prevent broken bones (fractures). See the separate leaflet called Osteoporosis to learn about this condition.

How are bisphosphonates administered?

The bisphosphonates that are usually prescribed for this are tablets. Those available in the UK are alendronate (the most used one), risedronate e ibandronic acid and they have various different marcas. In some circumstances, bisphosphonates can also be given by injection (intravenous bisphosphonates). The ones available in the UK for injection are ibandronic acid e zolendronic acid.

How do bisphosphonates work?

Bisphosphonates work by slowing down the cells which break down bone (osteoclasts). Therefore they slow down bone loss, allowing the bone cells (osteoblasts) that help to build the bone to work more effectively. They can help to strengthen bone and help to prevent it getting any weaker. People who take a bisphosphonate are less likely to break (fracture) a bone.

Who should have bisphosphonates?

Your doctor may prescribe a bisphosphonate if you:

• Have osteoporosis and have already had a broken bone (fracture). Bisphosphonates help in preventing bone fractures.

• Have a low bone density e your doctor thinks you are at risk of getting a bone fracture. Read more about risk factors in the leaflet called Osteoporosis.

• Take long courses (more than three months) of steroids (corticosteroids) - por exemplo, prednisolone tablets.You may also be prescribed bisphosphonates if you take repeated short courses of high-dose steroids. A common side-effect of taking steroids is to cause osteoporosis. See the separate leaflet called Preventing Steroid-induced Osteoporosis.

How long do bisphosphonates take to work?

It takes several months for bisphosphonates to work. Usually there is an increase in bone density 6-12 months after you start taking one. This then helps to prevent breaks (fractures) and bone pain of the spine, the hip, and other bones such as the wrist. But you can still have a fracture while you are taking a bisphosphonate - they do not totally reduce the risk risk. They usually need to be taken for some years to see the full effect.

How long should you stay on bisphosphonates?

Not everyone agrees on how long bisphosphonates should be taken for. Most doctors recommend that a bisphosphonate be taken for at least three to five years. After this they will review you to see if you still need to take it. You may not need to continue taking a bisphosphonate. However, some people need to take a bisphosphonate for longer. Your doctor will advise.

There is some evidence from studies that bisphosphonates keep working on the bone for a few years after the medicine has been stopped. It may also be that taking them for longer than five years does more harm than good. More studies are being done to find out exactly what should be recommended in terms of how long bisphosphonates should be taken.

Which bisphosphonates might I be prescribed?

In the UK, bisphosphonates are usually prescribed in the form of tablets:

Alendronic acid
Usually taken once a week, although ácido alendrônico is also available as a daily tablet. This is also available as a liquid for people who have difficulty swallowing the tablets, although it is much more expensive for the NHS.

Risedronate
Risedronate is taken usually once a week, although also available as a daily tablet.

Ibandronic acid
Ibandronic acid is taken once a month (also available as an injection - see below).

Bisphosphonate injections

Bisphosphonate injections might be used in some cases - for example, if the tablets give you too many side-effects, or if you are at greater risk of fractures:

Ibandronic acidAn injection into your vein every three months. Each ibandronic acid injection takes less than a minute.

Ácido zoledrônico
This is an infusion once a year. Zolendronic acid is slowly given into the vein over at least 15 minutes. You will need a blood test before each infusion, to check on your calcium, vitamin D, magnesium levels and kidney function. Injections are usually given by a specialist nurse.

How to take bisphosphonate tablets

Bisphosphonates are taken either once a day, once a week (on the same day of the week), or once a month (on the same day of the month), depending on the one prescribed. Most people take their bisphosphonate first thing in the morning before they eat or drink anything. If you take a bisphosphonate with food, or drinks other than water, only a small amount of the medicine is absorbed.

You need to wait between 30 minutes and 2 hours before eating or drinking anything (other than water). The information leaflet that comes with your tablets will tell you exactly how long you should wait.

You need to swallow the tablet with a full glass of water and sit upright for 30 minutes afterwards. This is because bisphosphonates can irritate the upper part of your gullet (oesophagus - the tube that takes food and drink from your mouth to your stomach).

When taking bisphosphonates

Algumas considerações importantes são:

• What to do if you forget to take your tablets.

• Have regular dental check-ups.

• What to do if you have heartburn or difficulty swallowing.

• Take calcium and vitamin D tablets.

• Do not take certain other medicines.

What to do if you forget to take your tablets

• If you are taking a once-a-day bisphosphonate: skip the missed tablet for that day and continue taking them as usual the next day.

• If you are taking a once-a-week bisphosphonate: take the missed tablet when you remember and take the next tablet when it is normally taken. Do not take more than two tablets on the same day.

• If you are taking a once-a-month bisphosphonate and you are due to take your tablet within the next seven days then do not take another tablet. Take another tablet on the day you are next due to take one.

• If you are taking a once-a-month bisphosphonate and you are due to take your next tablet in more than seven days then take the tablet when you remember (in the morning). Do not take two tablets within the same week.

Regular dental check-ups

You must tell your dentist if you are taking a bisphosphonate. You will need to have regular dental check-ups. Also it is advisable to have a dental check-up before starting a bisphosphonate. This is because there is a very small chance that you will get a condition called osteonecrosis of the jaw.

In this rare condition the jawbone does not receive enough blood and the bone starts to weaken and die. It is usually painful, but not always. In most people, this goes away after they have stopped taking their medicine.

Heartburn or difficulty swallowing

Bisphosphonates can sometimes cause dificuldade para engolir, pain when you swallow, chest pain, or new/worsened heartburn. You must stop taking the bisphosphonate and speak with your doctor if you have any of these problems. Your doctor may consider prescribing a different bisphosphonate or a different type of medicine to help prevent broken bones (fractures).

Calcium and vitamin D

You need calcium and vitamin D to make bone. Many doctors will usually also prescribe calcium and vitamin D if you take a bisphosphonate. This is in order to make sure there is enough calcium and vitamin D in your body. There are quite a few calcium and vitamin D preparations. They include: a chewable tablet, an effervescent tablet, or a sachet. They can be prescribed as a combination of the two, just calcium, or just vitamin D.

Your doctor will advise which one is right for you. Your doctor will ask about your diet. If you are already having enough calcium in your diet, you should not take calcium supplements as well. This is because too much calcium may be harmful for you. Calcium and vitamin D are normally taken every day (at a different time to the bisphosphonate).

Tomando outros medicamentos

Bisphosphonates sometimes react with other medicines that you may take. So, make sure your doctor knows of any other medicines that you are taking, including ones that you have bought rather than been prescribed. Always check with your pharmacist before you buy any painkillers from the pharmacy or supermarket. Some painkillers - for example, ibuprofeno e aspirina - can irritate your gullet (oesophagus) if you take them with a bisphosphonate.

What are the side-effects of bisphosphonates?

The most common side-effects of bisphosphonates include:

• Sentindo-se mal (náusea).

• Indigestion and heartburn (dyspepsia).

• Dor na barriga (abdominal).

• Diarreia.

• Constipação.

These side-effects usually happen in the first month of treatment but usually go away after this and do not last long-term. The benefits of taking bisphosphonates usually outweigh the risks.

Other common side-effects are joint, and/or muscle pain (usually not severe). This pain can happen a few days or a few months after you first start treatment. This pain normally goes away after you stop taking a bisphosphonate. A full list of possible side-effects (each of which will only happen to a few people) is included in the leaflet which comes with the medicine.

Less common side-effects

Less commonly some people experience more serious side-effects to their gullet (oesophagus). The oesophagus is the upper part of the digestive system, the food pipe that carries food and drink from your mouth to your stomach. Sometimes bisphosphonates can cause inflammation or ulcers of the oesophagus, or a narrowing of the oesophagus.

Taking the medicine carefully according to the instructions makes these side-effects less likely. As mentioned above, if you develop any symptoms such as difficulty or pain swallowing, worsening heartburn, or chest pain, you should stop the tablets and see your doctor. There have been very rare reports of bisphosphonates possibly causing cancer of the oesophagus but there is no definite evidence for this currently.

Some studies have also suggested that bisphosphonates may cause an increased risk of fibrilação atrial.

Rare side-effects

A rare side-effect is osteonecrosis of the jaw or ear canal (external auditory canal). This occurs when the jawbone does not receive enough blood, and the bone starts to weaken and die. You must stop taking bisphosphonates if this happens.

These medicines sometimes react with other medicines that you may take. So, make sure your doctor knows of any other medicines that you are taking, including ones that you have bought rather than been prescribed.

Can I buy bisphosphonates?

You cannot buy bisphosphonates. They are only available from your chemist, with a doctor's prescription.

Who should not take bisphosphonates?

You cannot take a bisphosphonate if:

• You have low calcium levels in your blood (hypocalcaemia).

• You have uncorrected deficiência de vitamina D.

• Você está grávida ou amamentando.

• Your kidneys do not work very well.

• You cannot sit upright or stand for 30 minutes after you have taken the tablet.

• You have structural problems with your gullet (oesophagus) which slows down the length of time it takes for the bisphosphonate to reach your stomach. Examples of these include: a narrowing of the oesophagus, or Esôfago de Barrett.

In addition, you may not be able to take a bisphosphonate if you have a recent history of tummy problems such as úlceras estomacais, úlceras duodenais or inflammation of the upper gut.

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