Alendronate Sodium (Fosamax)

What is it?

Alendronate Sodium reduces the amount of calcium lost from bones and increases the density of bones.

FDA approved:

September 1995

Brand Names and International Availability:

Fosalan (Israel); Fosamax (US)

How does it work?

Osteoclasts cause bone reabsorption. Alendronate Sodium inhibits osteoclast production thereby lessening reabsorbtion and causing an increase in bone density. It is used for the treatment of osteoporosis and Paget’s Disease.


For the treatment of osteoporosis, the recommended daily dose is 10mg. For the prevention of osteoporosis the recommended dose is 5mg daily. And for the treatment of Paget’s Disease the dose recommended is 40mg daily for 6 months.

How should I take it?

There are some very specific instructions for taking Alendronate Sodium.

1. After getting up for the day, swallow your alendronate sodium tablet with a full glass (6-8 oz) of water. 

2. After swallowing your alendronate sodium tablet do not lie down–stay upright (sitting or standing) for at least 30 minutes and until after your first food of the day. This will help the tablet reach your stomach quickly and help avoid irritation of your esophagus.

3. After swallowing the tablet, wait at least 30 minutes before taking your first food, beverage, or other medications. Alendronate sodium must be taken on a totally empty stomach.

4. Do not take alendronate sodium at bedtime or before getting up for the day. 

7. It is important that you continue taking alendronate sodium for as long as your doctor prescribes it. Alendronate sodium can treat your osteoporosis or help you from getting osteoporosis only if you continue to take it.

8. If you miss a dose do not take it later in the day. Continue your usual schedule of 1 tablet once a day the next morning.


Alendronate sodium should not be used by people with esophageal abnormalties.

Caution should be used when it is taken by anyone with a history of GI problems.

Alendronate sodium is not recommended in those with kidney disease.

Alendronate sodium should be used during pregnancy only if the potential benefit justifies the potential risk.

Alendronate sodium should not be used by nursing mothers.

Drug Interactions:

Antacids, calcium supplements and some vitamins will decrease the effect of alendronate sodium. Wait at least 30 minutes after taking alendronate sodium to take them.

Taking with aspirin increases the risk of GI irritation.

Because of the potent nature of this medicine, be sure to tell your doctor about any other medicines you are taking, including nonprescription medicines and vitamins.

Possible side effects:

These side effects are not considered serious but are certainly annoying for those experiencing them. The most frequently reported side effects include diarrhea or constipation, headache, stomach gas or fullness, nausea, changes in taste, and muscle pain.

More serious side effects that you should report right away include stomach pain, heartburn, pain or difficulty swallowing, black or tarry stools, skin rash, itching (hives)and facial swelling.

Signs of a possible allergic reaction are rash, swelling and difficulty breathing. These symptoms should be reported immediately. 

Precautions & Special Notes:

If you begin to have pain when swallowing, difficulty swallowing, heartburn or stomach pain, call your doctor right away.

Follow ALL instructions. 

Eat a diet rich in calcium and vitamin D.

If you get black, tarry stools or vomit up what looks like coffee grounds, call your doctor at once. You may have a bleeding ulcer.

For more information:

RxList Alendronate

MedicineNet Alendronate

Pharm Info Net Alendronate

Mosby’s GenRx®, 10th ed. Copyright © 2000 Mosby, Inc.
Complete Guide to Prescription and Nonprescription Drugs, H. Winter Griffith, M.D. , Copyright © 1997