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What is Fosamax (alendronate)?

Fosamax (alendronate) belongs to a group of drugs called bisphosphonates.

The FDA has approved the medicine for treating and preventing many osteoporosis-related (bone loss) conditions.

While there has been a lot of controversy about this medicine, Fosamax remains safe and effective for long-term use. It provides bone protection for over a decade after you take it.

Fosamax is available in the following dosage formats¹:

  • Oral tablet (daily): 5mg, 10mg, 40mg

  • Oral tablet (weekly): 35mg, 70mg

  • Oral liquid solution: 75ml (70mg/75ml)

What is Fosamax used to treat?

As you age, your body becomes more prone to developing osteoporosis. Osteoporosis is a condition that makes the bones weak and easy to break. Some groups of people are more prone to developing osteoporosis.

Fosamax has been approved to prevent and treat certain types of osteoporosis in adults, including:

  • Osteoporosis in women after menopause

  • Osteoporosis in men

  • Osteoporosis caused by some medications

Fosamax is also used to control Paget’s disease of the bone. Paget’s disease is a chronic skeletal condition that progresses slowly over time. It causes abnormally fast bone destruction (osteolytic) and reformation (osteoblastic).

Fosamax improves bone health. It works by helping the bones stay healthy and strong, slowing bone loss, and increasing bone thickness. This helps prevent bone fractures.

How do you take Fosamax?

Follow your doctor or pharmacist’s instructions carefully when taking Fosamax.

If you are prescribed Fosamax as an oral tablet, you will be instructed to take it daily or once per week.

  • Take Fosamax (oral solution or tablet) on an empty stomach first thing in the morning. Food can decrease the absorption of this medicine.

  • Never take Fosamax before going to bed at night.

  • Do not take Fosamax with any liquid other than plain water. Do not take the drug with other liquids, like tea, coffee, carbonated water, or mineral water.

  • Fosamax can irritate the esophagus and stomach. Do not bend or lie down for at least 30 minutes after taking the medicine.

  • Wait for at least 30 minutes after taking Fosamax to take other medicines (including vitamins, calcium, and antacids).

Seeing results

Fosamax improves bone health within a month of treatment and plateaus between three and six months. The effects of the medicine remain for several years after treatment.

Potential side effects of Fosamax

Like all medicines, Fosamax can cause side effects. Most common side effects disappear as your body adjusts to the drug.

Common side effects

Common side effects of Fosamax include:

  • Heartburn

  • Upset stomach

  • Stomach pain

  • Gas (flatulence)

  • Dizziness or vertigo

  • Nausea

  • Diarrhea

  • Constipation

  • Bone pain

  • Muscle pain

  • Joint pain

  • Swelling in the ankles or feet

This list is not exhaustive, and other side effects may occur. Talk to your doctor if these symptoms persist and bother you for more than a few days.

Serious side effects

Fosamax can cause severe side effects. Call your doctor immediately or seek medical assistance if you experience any of the following serious side effects:

  • Chest pain

  • Severe heartburn

  • Worsening of existing heartburn

  • Burning pain under the ribs or in the back

  • Excruciating or burning pain in the upper stomach

  • Coughing up blood

  • Unusual pain in your thigh or hip

  • Jaw pain

  • Numbness

  • Swelling

  • Severe joint, bone, or muscle pain

  • Muscle spasms or cramps

  • Numbness or tingling around your mouth, in your fingers, or toes

Seek immediate emergency medical help if you experience any symptoms that you believe to be life-threatening.

Long-term use of Fosamax

Fosamax is a long-term medicine, and your doctor might prescribe it to you to take over several years. However, long-term use of Fosamax can lead to serious conditions like atypical femoral fractures (fractures in the thigh bone), osteonecrosis (loss of bone) of the jaw, and esophageal cancer.

Your doctor will regularly monitor your condition and change your dosage.

Missed doses

You must only take Fosamax in the morning on an empty stomach. Do not take Fosamax at any other time of the day.

Follow this guide for what to do if you miss a dose:

  • Daily dose: Skip the missed dose and take the next dose as scheduled.

  • Weekly dose: Take the missed dose on an empty stomach in the morning after your missed dose.

Do not double up on your daily/weekly dose.


Using more Fosamax than prescribed can lead to Fosamax overdose and serious side effects like hypocalcemia and hypophosphatemia.

Symptoms of Fosamax overdose include:

  • Upset stomach

  • Heartburn

  • Swelling (inflammation) of the esophagus

  • Bloody vomit

  • Difficulty or pain when swallowing

  • Bloody or black and tarry stools

  • Stomach ulcer

If you suspect you or someone you know has overdosed on Fosamax, seek immediate emergency medical assistance.

Allergy information

Fosamax can cause an allergic reaction in some people.

Symptoms include:

  • Wheezing

  • Hives

  • Difficulty breathing

  • Swelling of your face, throat, lips, or tongue

If you notice any of these symptoms, stop taking Fosamax and seek emergency medical help.

Do not take Fosamax if you have ever had a previous allergic reaction to this medicine.

What to discuss with your doctor before taking Fosamax

Before you start using Fosamax, discuss the following with your doctor:

  • Drug allergies: Let your doctor know if you have any drug allergies, including a previous allergy to Fosamax or its ingredients.

  • Medications: Give your doctor a complete list of prescription and non-prescription medications you take, especially aspirin, antacids, and non-steroidal anti-inflammatory drugs (NSAIDs). Describe any herbal or vitamin supplements you take. Keep your doctor informed of any new medicines you start or stop taking during Fosamax treatment.

  • Medical conditions: Inform your doctor of your medical history, especially if you have had kidney problems, vitamin D deficiency, problems with the esophagus (the tube connecting your mouth and stomach), and digestive or stomach problems. Let your doctor know if you have a dental problem.

  • Pregnancy/breastfeeding: Inform your doctor if you are pregnant, breastfeeding, or planning to conceive while taking Fosamax.

  • Surgeries: Let your doctor know if you plan to have dental surgery. Fosamax must not be taken before dental surgery.

Stopping Fosamax

Do not stop taking Fosamax without consulting your doctor. You have been prescribed Fosamax because your doctor believes you can benefit from it.

If you want to stop taking Fosamax because of side effects, let your doctor know about your concerns. They may be able to suggest an alternative drug to treat your condition.

Who should not take Fosamax

Fosamax might not be suitable for you if:

  • You have had a previous allergic reaction to Fosamax

  • You suffer from problems with the esophagus; for example, if you have difficulty swallowing or suffer from ulcers, irritation, or inflammation of the esophagus

  • You have hypocalcemia (low levels of calcium in your blood)

  • You cannot sit up straight or stand for 30 minutes

  • You will have a tooth removed or undergo another type of dental surgery

  • You have kidney problems

  • You have malabsorption syndrome (your stomach and intestines find it hard to absorb minerals)

  • You are pregnant or breastfeeding

  • You are under 18

Fosamax and pregnancy

Bisphosphonates like Fosamax (alendronate) cross the placenta.

No Fosamax studies have been carried out on pregnant women, but animal studies have shown adverse effects on the fetus. Fosamax is not recommended during pregnancy and should only be prescribed if its benefits outweigh the risks.

Since Fosamax stays in the body for years after treatment, you should tell your doctor if you plan to become pregnant after taking the drug.

Fosamax and breastfeeding

There is not enough data on whether Fosamax can pass to a nursing infant through breast milk, and risks cannot be ruled out. Talk to your doctor about the pros and cons of using this medicine while breastfeeding.

Interactions with other drugs

Fosamax is known to interact with some drugs. Taking drugs that interact could change how they work or cause harmful side effects.

Fosamax interacts with the following drugs:

  • Antacids

  • Aspirin

  • Aluminum salts

  • Chemotherapeutic drugs

  • Hormone replacement therapy (HRT)

  • Iron salts

  • Zinc salts

  • Lithium (Lithobid)

  • Supplements containing magnesium or calcium

  • Angiogenesis inhibitors, such as everolimus (Afinitor or Zortress) and bevacizumab (Avastin)

  • Oral steroids, such as prednisone (Prednisone Intensol, Rayos, or Sterapred) and dexamethasone (Decadron, Dexamethasone Intensol, or Dexpak Taperpak)

  • NSAIDs, such as diclofenac (Cambia, Zipsor, or Zorvoflex) ibuprofen, meloxicam (Mobic), and naproxen (Aleve, Anaprox, Naprosyn, and others)

  • Diuretics, such as furosemide (Lasix) and bumetanide

This is not an exhaustive list. Fosamax can interact with other drugs. Keep your doctor informed of any new medication you start or stop taking during Fosamax treatment.

Drug approval history

Fosamax has been shown to effectively reduce fractures and treat osteoporosis and Paget’s disease. There is, however, no consensus on how long the drug should be used.

1995: The FDA approves Fosamax (alendronate sodium) oral tablets, manufactured by Merck.

2003: The FDA approves Fosamax oral solution.

2008: A generic version of Fosamax is approved by the FDA.

Tips and advice for taking Fosamax

Follow the following tips and advice to help you take Fosamax safely and effectively:

  • Always take Fosamax exactly as prescribed by your doctor.

  • Fosamax must always be taken on an empty stomach when you get out of bed in the morning.

  • Remain upright for 30 minutes after taking the medication.

  • Do not take Fosamax with any liquid other than plain water.

  • Keep Fosamax out of reach of children.

  • Inform your doctor immediately if you develop leg or groin pain, as Fosamax has been reported to cause broken bones or fractures in the thigh bones.

  • If you are scheduled to have dental surgery or tooth removal, let the surgeon/dentist know that you are taking Fosamax. The medicine must be stopped before any dental work takes place.

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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.