Fosamax (Alendronic acid)
How does it work?
Fosamax tablets contain the active ingredient alendronic acid (as sodium alendronate), which is a type of medicine called a bisphosphonate. (NB: Alendronic acid tablets are also available without a brand name, ie as the generic medicine.) Bisphosphonates are medicines that prevent the breakdown of bone.
Bone is not a static structure. It is continually shaped, reformed and rebuilt by cells called osteoblasts and osteoclasts. These cells continously deposit and remove calcium and phophorous, stored in a protein network that makes up the structure of the bone. Old bone is broken down by the osteoclasts and new bone is formed by the osteoblasts.
In menopausal women blood levels of the female hormone oestrogen start to decrease. This results in an increase in breakdown of bone by the osteoclasts, which can lead to a loss of bone density. Bone loss is particularly rapid for the first ten years after the menopause and it may lead to the development of osteoporosis a condition in which the bones become weak and brittle and break (fracture) more easily.
Osteoporosis can also occur in men and as a result of long-term treatment with corticosteroid medicines such as prednisolone. Other risk factors include smoking, a family history of osteoporosis, early menopause and thin body build.
Alendronic acid is used both to prevent bone loss in people who are at risk of developing osteoporosis, and to prevent fractures in people who already have osteoporosis. The medicine works by binding very tightly to the bone and preventing the calcium being removed by the osteoclasts. This stops the osteoclasts from breaking down the bone, which helps to keep the bones strong and less likely to break.
As this medicine slows bone turnover and so prevents calcium being rebsorbed from the bones into the blood, it can cause the amount of calcium in your blood to fall to a low level. If your dietary intake of calcium and vitamin D is low, your doctor may ask you to take supplements to prevent this.
What is it used for?
- Preventing bone loss in women who have passed the menopause who are at risk of developing osteoporosis.
- Treatment of osteoporosis in women who have passed the menopause to prevent fractures.
- Treatment of osteoporosis in men to prevent fractures.
- Prevention and treatment of osteoporosis caused by long-term treatment with corticosteroids such as prednisolone.
How do I take it?
- It is very important that the instructions for taking these tablets are followed completely. This is because when alendronic acid is taken by mouth it can cause irritation and ulceration of the foodpipe (oesophagus). Following the instructions below minimises this risk. If you are unclear about anything ask your pharmacist for advice.
- One 10mg tablet is taken once a day.
- Your tablet should be taken in the morning at least 30 minutes before the first food, drink or medicine of the day.
- The tablet should be swallowed whole with a glass of plain water (at least 200ml, not mineral water) while you are sitting or standing in an upright position. Do not crush, chew or suck the tablet.
- You should not lie down for at least 30 minutes after taking the tablet.
- You should not eat or drink anything other than plain water for at least 30 minutes after taking the tablet. This is because food and some drinks (including mineral water) can interfere with the absorption of the medicine from the gut and hence make it less effective.
- You should not take any other medicine by mouth at the same time as this tablet, or for at least 30 minutes after taking the tablet. See the end of this factsheet for more details.
- If you experience any signs of irritation to your foodpipe during treatment with this medicine, for example new or worsening problems with swallowing, pain on swallowing, pain behind your breastbone, or heartburn, you should stop taking these tablets and inform your doctor.
- Your doctor may want you to have regular blood tests to monitor the level of calcium in your blood while you are taking this medicine.
- The class of medicines that alendronic acid belongs to (bisphosphonates) has been associated with a rare condition called osteonecrosis of the jaw. The majority of cases of this condition have been in cancer patients treated with bisphosphonates by injection into a vein, and many of these people were also having treatment with chemotherapy or corticosteroids. However, the condition has also been seen in people taking bisphosphonates by mouth. The risk may also be increased by poor oral hygiene, dental problems such as gum disease or poorly fitting dentures, teeth extractions, oral surgery and smoking. For this reason, you should have a dental examination and, if necessary, appropriate preventive dentistry, before you start treatment with this medicine. Discuss this with your doctor. It is important to look after your mouth and teeth as much as possible while you are taking this medicine. You should have regular check-ups with your dentist and get advice straight away if you have any problems with your mouth or teeth. When you see a dentist during treatment, make sure they know you are taking this medicine. Invasive dental procedures such as tooth extraction or surgery should be avoided if possible.
- Some people being treated with bisphosphonates (mainly people having long-term treatment for osteoporosis) have experienced an unusual fracture of their thigh bone. For this reason it is important to let your doctor know if you get any pain in your thighs, hips or groin while you are having treatment with this medicine. These symptoms could be an early indication of a possible fracture.
Use with caution in
- Decreased kidney function.
- People with active disorders of the upper part of the digestive system, such as difficulty swallowing, disorders affecting the foodpipe (eg reflux disease), ulcers, inflammation of the lining of the stomach (gastritis), inflammation of the small intestine (duodenitis).
- People who have had major disorders of the upper part of the digestive system in the last year, eg peptic ulcer, bleeding from the stomach or intestines, or surgery on the stomach or intestines.
- Disorders of the parathyroid gland (gland that produces hormones responsible for regulating calcium metabolism).
- Vitamin D deficiency.
Not to be used in
- People who have any abnormalities of the food pipe (oesophagus).
- People with conditions that cause delayed passage of food through the foodpipe (oesophagus), eg narrowing or obstruction of the foodpipe.
- People who cannot stand or sit upright for at least 30 minutes.
- People who have a low level of calcium in their blood (hypocalcaemia).
- Rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption (Fosamax tablets contain lactose).
This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.
Pregnancy and breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
- This medicine has not been studied in pregnant women, hence its safety has not been established. It should not be used during pregnancy.
- It is not known if this medicine passes into breast milk. It should not be used by breastfeeding mothers.
Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.
Common (affect between 1 in 10 and 1 in 100 people)
- Disturbances of the gut such as diarrhoea, constipation, indigestion, flatulence, acid reflux or abdominal pain.
- Ulceration of the food pipe.
- Difficulty swallowing.
- Pain in the joints, muscles or bones.
Uncommon (affect between 1 in 100 and 1 in 1000 people)
- Inflammation of the food pipe (oesophagitis).
- Inflammation of the stomach (gastritis).
- Dark coloured, tarry stools, due to the presence of blood altered by the intestinal juices (melaena).
- Skin reactions, such as itching, rash and redness.
Rare (affect between 1 in 1000 and 1 in 10,000 people)
- Ulceration, bleeding or perforation of the stomach or intestines.
- Low level of calcium in the blood (hypocalcaemia). This may cause symptoms such as pins and needles or muscle spasms/twitches/cramps. Tell your doctor if you experience symptoms like these.
- Inflammation of the middle layer of the eyeball (uveitis).
- Osteonecrosis of the jaw (see warning section above).
- Unusual fractures of the thigh bone (see warning section above).
Very rare (affect less than 1 in 10,000 people)
- Severe allergic skin reactions.
- Spinning sensations.
- Hair loss.
- Swelling of joints.
- Swelling of hands and feet.
- Feeling weak.
The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.
For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.
How can this medicine affect other medicines?
It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.
Other medicines may interfere with the absorption of alendronic acid from the gut and could therefore make the medicine less effective. For this reason, you should not take other medicines by mouth at the same time as Fosamax, or for at least 30 minutes after taking it. This is particularly important for the medicines listed below:
- antacids (indigestion remedies)
- calcium supplements
- iron supplements
- laxatives containing magnesium
- mineral supplements
- multivitamins containing minerals such as calcium, iron, magnesium or zinc
- zinc supplements.
There may be an increased risk of irritation to the foodpipe (oesophagitis) or digestive tract if non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, diclofenac or indometacin are taken in combination with this medicine. These types of painkiller are best avoided by people taking this medicine. Ask your pharmacist for further advice.
There may an increased chance of the amount of calcium in the blood falling too low if aminoglycoside antibiotics such as gentamicin are used in combination with this medicine.
Other medicines containing the same active ingredient
Alendronic acid daily tablets (10mg) and once weekly tablets (70mg) are also available without a brand name, ie as the generic medicine.
Fosavance contains alendronic acid in combination with vitamin D.