Alendronate (a·luhn·drow·nayt) is a medication used to treat or prevent osteoporosis (loss of bone strength) and to treat other conditions that cause bones to weaken, such as Paget's disease.¹ ²

Alendronate, also known as alendronic acid, belongs to a class of drugs called bisphosphonates. It is only available with a doctor’s prescription. Alendronate is available as a generic drug or under the brand names Binosto and Fosamax. Alendronate works by slowing bone loss and increasing bone mineral density.³

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What is alendronate used to treat?

Alendronate is a medication used mainly to treat osteoporosis (weakening of the bones) in postmenopausal women. It can also treat Paget's disease of the bone and osteoporosis caused by corticosteroid use. Alendronate works by slowing down bone loss and helping to rebuild bones.¹

How do you take alendronate?

Alendronate comes in a tablet, effervescent tablet (to dissolve in water), or an oral solution. Take alendronate first thing in the morning, before you eat or drink anything.

Alendronate tablets should be swallowed whole. Do not chew or dissolve them in your mouth.

Do not lie down right immediately after taking alendronate. Instead, maintain an upright posture (sit, stand, or walk) for at least half an hour. To reduce the risk that the tablet will irritate your esophagus, it should reach your stomach as quickly as possible.

Take your alendronate tablet at least half an hour before having your first drink or food of the day. Also, take it before any other medications (unless directed differently by your doctor).

Alendronate is most effective when taken on an empty stomach.

Do not miss any follow-up visits to your doctor for tests or checkups.


Alendronate comes in tablets, effervescent tablets to dissolve in water, or an oral solution.

Alendronate is available in the following strengths and formats:

Tablet (5mg, 10mg, 35mg, 40mg, 70mg)

Effervescent tablet (70mg)

Oral solution (70mg per 75mL)

A typical osteoporosis prevention dose is:

  • 35mg weekly or 5mg daily (taken orally)

A typical osteoporosis treatment dose:

  • 70mg weekly or 10mg daily (taken orally)

Typical Paget’s disease management dose:

40mg daily for a course of 6 months (taken orally) Always follow your doctor’s instructions and take medication as prescribed.

Seeing results


Most people who take alendronate for osteoporosis have a change in bone markers that indicate effectiveness (bone resorption) about a month into treatment. These changes typically level off around three to six months into treatment.⁴ Monitoring may happen with blood and urine tests first.⁵ Then, your doctor will usually order a bone density test (dual-energy X-ray absorptiometry) within one to two years.⁶ Alendronate can slow down bone loss but cannot stop it completely. Therefore, take alendronate for as long as your doctor indicates.

Paget’s disease of bone

In one study that followed patients with Paget’s disease for almost 12 years, it took an average of three to four months of taking 70mg of alendronate a week to achieve remission.⁷ Typical monitoring occurs every three to six months with an alkaline phosphatase test (ALP) taken by blood sample.⁸

Potential side effects of alendronate

Common side effects

The most frequent side effects of alendronate are gastrointestinal. Typical side effects may include:  

  • Diarrhea

  • Heartburn

  • Nausea

  • Constipation

  • Abdominal pain

  • Gas or bloating

  • Headache

  • Muscle, bone, or joint pain

Less common side effects

Infrequent sides effects of alendronate may include:

  • Low blood calcium levels (hypocalcemia)

  • Irritation or ulceration of the tube between your mouth and stomach (esophagus) 

  • Allergic reactions

Severe side effects

Alendronate can cause severe side effects. These may include:

  • Eye pain, loss of vision, sensitivity to bright light

  • Ulceration of the esophagus (ulcer between the throat and stomach)

  • Osteonecrosis of the jaw (ONJ) (exposure of the jaw bone)

  • Severe joint, muscle, and bone pain

  • Atypical femur fractures⁹

Talk to your doctor about any side effects. If you experience severe side effects while taking alendronate, seek medical attention immediately.

Long-term use of alendronate

Alendronate is considered effective in the long-term management of osteoporosis. 

For example, alendronate increased bone mineral density in a study of postmenopausal women with osteoporosis. It also decreased the risk of vertebral fractures over four years.¹⁰

If you take alendronate for osteoporosis, you will likely take it for three to five years, possibly longer depending on your doctor’s ongoing assessment of your treatment needs.¹¹

Your doctor may recommend stopping alendronate after six months if you take it for Paget’s disease.¹²

Alendronate is a first-line treatment for osteoporosis, but there are concerns about its long-term safety.¹⁰

Missed doses

If you forget to take alendronate, do not take two doses the next day. Just skip the missed dose and go back to your regular schedule. Do not take more or less alendronate than prescribed by your doctor.


Alendronate should be stored at room temperature, away from light and moisture. Do not store alendronate in the bathroom. Also, keep alendronate away from children and pets.


Numbness, tingling, muscle cramps, irritability, convulsions, or unusual behavior or thoughts could indicate an alendronate overdose.¹³

If you have taken more than the prescribed amount of alendronate or have taken it accidentally, go to the nearest emergency room immediately.

What to discuss with your doctor before taking alendronate?

Before starting to take alendronate, talk with your doctor about:

  • Your complete medical history.

  • Allergies you have or past allergic reactions to medications (especially alendronate).

  • Medications you currently take (prescribed or non-prescribed), including vitamins and supplements.

  • Whether you are pregnant or trying to get pregnant. 

  • Whether you are currently breastfeeding or planning to breastfeed. 

  • Upcoming medical or dental procedures (or plans to have one). 

  • Whether or not you consume alcohol, how much, and how frequently.

  • Your lifestyle and dietary habits.

Your doctor needs to know about any other medical conditions you have, especially kidney disease or low blood calcium levels. 

Alendronate is not suitable for everyone, so it's essential to have an open and honest conversation with your doctor before starting treatment.

Stopping alendronate

Do not stop taking alendronate without speaking to your doctor first. Stopping alendronate may cause bone loss and increase the risk of fractures.

If alendronate proves ineffective for you, your doctor will advise you about appropriate alternatives.

Alendronate and pregnancy

Alendronate is not recommended for use in pregnant women. It is a Category C drug under the US Food and Drug Administration (FDA) classification system. If you are thinking about becoming pregnant or becoming pregnant while taking alendronate, contact your doctor immediately.

Alendronate and breastfeeding

It is unknown whether or not alendronate passes into breast milk. If breastfeeding, talk to your doctor about the risks of taking alendronate.

Alendronate and children

Alendronate is not recommended for those under 18 years of age and can cause serious side effects in children.

Interactions with other drugs

Alendronate can interact with other medications, vitamins, or supplements you might be taking. Tell your doctor about everything you're taking, especially:

  • Antacids, calcium supplements, or multivitamins Calcium, antacids, and mineral multivitamins can interfere with the absorption of alendronate. Speak to your doctor or a pharmacist for guidance on how to time these throughout your day.

  • Furosemide (Lasix) Using this diuretic, also known as a “water pill” with alendronate may decrease levels of calcium in your blood. If you are prescribed alendronate while taking a diuretic, follow your doctor’s instructions exactly.

  • Aspirin Check with your doctor before using aspirin while taking alendronate. Doing so may increase the risk of gastric ulcers.

  • NSAIDs Nonsteroidal anti-inflammatory drugs such as Aleve (naproxen may contribute to ulcers).¹⁴

If you're taking alendronate with any of these drugs, your doctor will closely monitor you for side effects. They may need to adjust your dosage or change your medication altogether.

Only take alendronate with plain water. Do not take it with juice, coffee, soda, tea, or mineral water. Do not take alendronate within 30 minutes of taking calcium supplements or antacids. Doing so could reduce the effectiveness of the alendronate and increase your risk for side effects.

Alendronate is usually one part of a complete treatment program that also includes dietary intervention, exercise, bone density testing, and taking calcium and vitamin D supplements. 

Follow your doctor's instructions carefully while taking alendronate.

Allergy information

Alendronate can cause severe allergic reactions (anaphylaxis). Symptoms may include hives, rash, itching, difficulty breathing, tightness in the chest, and swelling of the mouth, face, lips, or tongue. If you experience any of these symptoms, seek medical attention immediately.

Before taking alendronate, tell your doctor about all allergies (especially previous allergic reactions to alendronate).

Clinical trial history

Alendronate is effective in postmenopausal women with osteoporosis with a bone mineral density below the premenopausal average.³

The alendronate brand Fosamax gained US Food and Drug Administration (FDA) approval in 1995.

Prior to approval, Fosamax was studied in five clinical trials featuring 1,827 postmenopausal women with osteoporosis. Participants were recruited from 16 different countries. The trial outcomes demonstrated a significant increase in bone mineral density. The number of women with new spinal fractures dropped (48%) as did the occurrence of new spinal fractures (63%). Overall height loss was reduced (35%).¹⁵

Tips and advice for taking alendronate

Here are a few to keep in mind when taking alendronate:

  • Take your dose with a full glass of plain water (not any other beverage).

  • Take alendronate at the same time of day.

  • Using alendronate requires the ability to sit or stand for at least 30 minutes (do not lie down for at least half an hour after taking your dose).

  • Speak to your doctor about whether or not supplementing with vitamin D or calcium while taking alendronate could be beneficial.

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Here at HealthMatch, we’ve done our best to ensure that the information provided in this article is helpful, up to date, and, most importantly, accurate.

However, we can’t replace the one-to-one advice of a qualified medical practitioner or outline all of the possible risks associated with this particular drug and your circumstances.

It is therefore important for you to note that the information contained in this article does not constitute professional medical or healthcare advice, diagnosis or recommendation of treatment and is not intended to, nor should be used to, replace professional medical advice. This article may not always be up to date and is not exhaustive of all of the risks and considerations relevant to this particular drug. In no circumstances should this article be relied upon without independent consideration and confirmation by a qualified medical practitioner.

Your doctor will be able to explain all possible uses, dosages, precautions, interactions with other drugs, and other potential adverse effects, and you should always talk to them about any kind of medication you are taking, thinking about taking or wanting to stop taking.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.