Alendronate (Oral)

Known as Fosamax in the US, alendronate is a bisphosphonate used most commonly in postmenopausal women to treat or prevent osteoporosis.


Alendronate, more commonly known by its US brand name alendronate, is a bisphosphonate drug designed to treat postmenopausal osteoporosis in women. It works by slowing down the resorption of bone tissue in order to increase bone density, which helps to maintain bone strength and reduce the risk of fracture associated with osteoporosis.

Although usually prescribed to women after menopause (since this is the time when osteoporosis is most common), alendronate is sometimes prescribed to men who suffer from osteoporosis too. It might also be prescribed to men and women who are suffering from osteoporosis caused by long-term corticosteroid use.

In some instances, alendronate is prescribed to help treat Paget's disease of bone. In this condition, the body's normal bone replacement processes are disrupted, meaning that when old bone tissue is replaced by new, the bones become misshapen and fragile. By slowing resorption of bone tissue, alendronate can help to reduce the progression of Paget's disease of bone.

Clinical trials have monitored the safety and effectiveness of alendronate over the course of four years. The medication is designed for long-term use, but patients are typically reevaluated periodically to assess the success of the treatment and look out for harmful side effects. Patients who are at a low risk of bone fracture may have the drug discontinued after three to five years of use, since alendronate can stay in the system for several years and it may no longer be necessary to continue taking it. However, in these cases, individuals should be reevaluated periodically to assess their risk of fracture.

Condition(s) treated?

  • Osteoporosis
  • Paget's disease

Type of medicine?

  • Bisphosphonate

Side Effects

Some side effects of Alendronate are mild and do not require medical attention. The most common of these include headache, nausea, constipation, diarrhea, unusual amounts of gas, and bloating. These side effects may dissipate as the body adjusts to the new medication but, if not, you could speak to your doctor about them for advice on lifestyle adjustments which might stop or reduce the severity of the side effects.

If constipation or diarrhea is prolonged, you may wish to consult your doctor for advice on a remedy. Prolonged diarrhea could lead to dehydration, so drink plenty of fluids. Eat more insoluble fiber, such as whole grains and wheat bran, to add bulk to stools and to make them less watery.

If constipation is left untreated, it can cause complications for the digestive system. Drink more fluids and eat more soluble fiber, such as beans, peas and fruits, to soften stools and make them easier to pass. Doctors may prescribe laxatives if constipation becomes very severe.

The following are known side effects of alendronate that occur so rarely that the incidence of them is unknown, and which do not usually require medical attention:

  • Blurred or otherwise changed vision
  • Pain in the eyes
  • Light sensitivity
  • Tearing of the eyes
  • Sensation of spinning or that you or your environment is moving
  • Hair loss or thinning hair

Some side effects of alendronate are serious and should be reported to a doctor immediately. The most common is abdominal pain or pain in the stomach. Less frequently, patients experience heartburn, pain or discomfort in the esophagus and difficulty swallowing. It's also been known for the drug to cause black, tarry stools or vomit which contains what looks like coffee grounds. All of these are signs of ulcers in the stomach or esophagus, which are serious and should be diagnosed and treated urgently.

In very rare instances, patients might experience pain or swelling in the joints or hips after taking alendronate. It's also possible to develop pain in the jaw. In these instances, report your symptoms to your doctor as soon as possible.

Although allergic reaction to alendronate is rare, it is possible. If you notice signs of allergic reaction, such as a rash, itching, swelling of the face, tongue or throat, dizziness or labored breathing, visit your doctor as soon as possible.

If you notice any other unusual symptoms when taking alendronate, discuss them with your doctor. They may not be things that require medical attention, but it's safer to mention them to your doctor so that they can be monitored. Often, side effects go away after a short time of taking a new medication, so it may simply be a case of waiting for your body to adjust. If side effects don't go away, your doctor may consider adjusting your dose or prescribing an alternative treatment, such as another type of bisphosphonate. You can also report side effects to the FDA if you feel that they are unusual.


Dosage of alendronate varies depending on the patient in question and their medical history.

For women who have osteoporosis after menopause, the recommended dosage is one 70 mg tablet once each week, or one 70 mg bottle of oral solution once each week, or one 10 mg tablet once each day. For postmenopausal women who are at risk of osteoporosis, the dosage is effectively halved to help prevent the condition, meaning that they will usually take either one 35 mg tablet once each week, or one 5 mg tablet once each day.

For men with osteoporosis, the recommended dosage of alendronate is one 70 mg tablet or oral solution once each week, or one 10 mg tablet once each day.

For men and women with osteoporosis caused by extended use of corticosteroids, the recommended dosage is one 5 mg tablet each day. However, postmenopausal women who are not undergoing estrogen replacement therapy are recommended to take one 10 mg tablet each day.

Individuals with Paget's disease of bone typically take 40 mg of alendronate each day for six months. The condition should then be evaluated every six months to decipher whether re-treatment is necessary.

How to take alendronate

Alendronate should be taken first thing in the morning each day, at least 30 minutes before food, drink or other medication. Only water should be consumed with the drug. Eating or drinking anything else will reduce the absorption of the medication and could make it less effective.

It is recommended that patients swallow the alendronate tablet with six to eight ounces of water. This should help to reduce irritation to the esophagus. Continue to sip a further two ounces of water to help the tablet be thoroughly absorbed. You should not lie down after taking the tablet for at least 30 minutes, which means you should take it only after you've got out of bed. Failure to follow this advice could cause irritation to the esophagus and could increase the risk of ulcers in the stomach or esophagus.

If patients are unable to sit or stand upright for 30 minutes following the administration of alendronate tablets, the treatment may not be suitable for them.

Missed doses

If you take alendronate tablets daily and realize you've missed a dose, simply skip the dose entirely and resume your normal dosing schedule. Do not double doses to catch up on a missed dose.

If you take alendronate once each week, take the missed dose on the morning after you remember. Don't take two doses on the same day, and once you've taken the missed dose, return to your normal schedule and take the next tablet on your originally chosen day.


Overdose of alendronate could result in the following symptoms:

In the event of overdose, do not induce vomiting as this could increase the risk of irritation to the esophagus. The patient should be kept upright, and milk or antacid medicines may be given to bind the alendronate.


Research has found that intravenous use of ranitidine (brand name Zantec, a medication used to decrease stomach acid production and treat stomach ulcers and GERD) doubles the bioavailability of oral alendronate, meaning that the body absorbs more alendronate than usual. It isn't clear what effect this has, but for this reason, doctors may avoid prescribing alendronate in patients who undergo intravenous ranitidine therapy.

It's also known that medications, supplements or vitamins which contain calcium or iron could affect the absorption of alendronate. For this reason, ask your doctor about any supplements that you are currently taking when you're prescribed alendronate. You may have to stop taking them, or you may simply have to take them at a different time of day to avoid reducing the effectiveness of the alendronate.

The following could also reduce the absorption of alendronate if consumed within 30 minutes of taking your dosage:

  • Antacids
  • Tea
  • Coffee
  • Soda
  • Mineral water


Alendronate is a bisphosphonate, which means that when consumed orally it can cause irritation to the upper gastrointestinal tract. For this reason, patients with a history of gastrointestinal problems may not be best suited to this treatment as it could exacerbate the underlying problem. However, if the benefits of the drug far outweigh the risks, doctors may continue to prescribe it. Examples of such gastrointestinal issues include:

All patients who take alendronate, whether they have previous gastrointestinal problems or not, should familiarize themselves with symptoms of esophageal ulcers and damage and report them to their doctor immediately. Examples of such symptoms include:

  • Increased frequency and severity of heartburn
  • Difficulty swallowing
  • Pain or discomfort in the esophagus
  • Coughing or vomiting blood
  • Vomiting a substance which looks like coffee grounds
  • Nausea

It is incredibly important to adhere to the administration instructions in regard to drinking water with alendronate tablets and avoiding lying down just after taking a dosage.

Taking alendronate during pregnancy

There has been too little research conducted into the effects of alendronate during pregnancy, so it is not known if it poses a risk to either the mother or the fetus. For this reason, the drug is categorized as C, meaning that it should only be used if the benefits of the drug far outweigh the potential risks.

Alendronate can stay in the body for several years after you have finished taking it. If you have been prescribed alendronate in the past (or are currently taking it) and are planning to have a baby or have just discovered that you are pregnant, speak to your doctor. They may prescribe an alternative medication or treatment.

It is not known whether alendronate can pass into breast milk or if it has an adverse impact on infants who are nursing. If you plan on breastfeeding and are taking alendronate, ask your doctor for advice.

Possible increased risk of thighbone fracture

In 2008, research from Singapore was released which suggested that long-term use of alendronate could increase the risk of thighbone fracture without major trauma. 17 women had reported fractures of this nature, 13 of which had pain in the leg before developing the fracture. All had been taking the drug for an average of five years. Subsequent research in New York found a similar trend, and found that alendronate could increase the risk of low-energy fractures in the thighbone.

It is believed that the reason for this is that alendronate slows down born resorption, which can impair the formation of new bone. This affects the bone's ability to repair the microscopic cracks which occur from normal wear and tear. If microscopic damage accumulates, a fracture may eventually occur. However, there is still much research to be done to fully understand the problem and assess how prevalent it is. Overall, the benefits of alendronate greatly outweigh the risk of thigh bone fracture.

Mineral metabolism of alendronate

Individuals with low calcium levels (hypocalcemia) or low vitamin D levels should treat these problems before beginning alendronate therapy. Once levels of calcium or vitamin D have reached a normal level, alendronate can be prescribed but mineral levels should continue to be monitored throughout treatment.

Patients undergoing therapy with alendronate may experience a drop in calcium and phosphate levels. This is particularly noticeable in those with Paget's disease of bone and those taking corticosteroids. Monitoring of these mineral levels is therefore important.

Bone, joint and muscle pain

Some people who take alendronate experience severe pain in the joints, muscles and bones. In these instances, stopping the medication usually rectifies the problem, but in some, the pain recurs when alendronate or an alternative bisphosphonate is prescribed. If the pain is very severe and outweighs the benefits of the drug, it is better to discontinue use of alendronate in these instances. Report painful symptoms to your doctor as soon as possible if you experience them.


Osteonecrosis (death of bone) of the jaw (ONJ) has been known to occur in patients taking bisphosphonates such as alendronate. The risk of this increases in patients who experience the following while taking alendronate:

  • Major dental procedures such as tooth extraction and dental implants
  • Cancer diagnosis
  • Chemotherapy
  • Periodontal disease
  • Anemia
  • Poor oral hygiene

To reduce the risk of ONJ, it is often recommended that alendronate is discontinued while patients undergo invasive dental procedures or other treatments which might lead to osteonecrosis.


Alendronate should be stored at room temperature, away from light and moisture. Do not keep it in a bathroom or bathroom cabinet, as the heat and moisture from the bath or shower could affect the medicine. Keep them in a secure container away from children and pets.

If you have expired or unused alendronate medication, ask your healthcare provider for advice on how to dispose of it correctly. Do not simply pour them down the toilet or drain or put them in the trash, as they could be harmful to the environment.


Alendronate, commonly known under its brand name Fosamax, is a bisphosphonate drug primarily used to treat or prevent osteoporosis in postmenopausal women. It might also be used to treat osteoporosis in men, osteoporosis caused by extended corticosteroid use, or to treat Paget's disease of bone.

The way alendronate works is to slow down the resorption of old bone tissue in order to make bones denser. This helps to reduce the thinning of bones and reduces the risk of fractures. It is designed for long-term use, and tends to be prescribed for at least 3 to 5 years after which point the risk of fracture will be reevaluated. The medication can stay in the body for several years, so in some cases it may be possible to discontinue use of the drug after this point.

The biggest risk of alendronate is esophageal irritation and ulcers. The drug can cause heartburn and irritate the lining of the esophagus and the stomach. In rare instances the effects are severe enough to cause hospitalization. Patients with a history of gastrointestinal illnesses are often not prescribed the drug, since their risk of developing esophageal irritation is increased. If the benefits of the drug outweigh the risks, however, it may be prescribed under close supervision and regular monitoring.

To minimize the risk of esophageal irritation, patients are advised to take alendronate first thing in the morning after they have got out of bed and before they eat or drink anything. The tablets or oral solution should be taken with plenty of water, and patients should wait at least 30 minutes (but preferably 1 to 2 hours) before eating anything or drinking any beverage other than water. They should also sit or stand up during this time and should not lie down, as doing so could cause esophageal irritation.

There have been some instances of long-term alendronate use leading to low-impact fractures of the thigh. It isn't fully understood why this problem occurs, but experts believe it is due to the way that bone resorption is reduced by the drug. Bone resorption is necessary for bone to repair microscopic cracks or damage, so if this process is slowed, microscopic damage to the bone might not be fully repaired and over time this might accumulate until full fracture occurs. However, the frequency at which this occurs is unknown, and the benefits of the drug far outweigh this potential risk.

Last Reviewed:
December 10, 2017
Last Updated:
April 04, 2018