Fosamax Uses, Dosage, Side Effects, Food Interaction and all others data.

Fosamax inhibits osteoclast-mediated bone-resorption. Like all bisphosphonates, it is chemically related to inorganic pyrophosphate, the endogenous regulator of bone turnover. But while pyrophosphate inhibits both osteoclastic bone resorption and the mineralization of the bone newly formed by osteoblasts, alendronate specifically inhibits bone resorption without any effect on mineralization at pharmacologically achievable doses. Its inhibition of bone-resorption is dose-dependent and approximately 1,000 times stronger than the equimolar effect of the first bisphosphonate drug, etidronate. Under therapy, normal bone tissue develops, and alendronate is deposited in the bone-matrix in a pharmacologically inactive form. For optimal action, enough calcium and vitamin D are needed in the body in order to promote normal bone development. Hypocalcemia should, therefore, be corrected before starting therapy.

Fosamax tablets have a very low oral bioavialability. After administration it distributes into soft tissue and bone or is excreted in the urine. Fosamax does not undergo metabolism.

Trade Name Fosamax
Generic Alendronic acid
Alendronic acid Other Names ABDP, Acide Alendronique, Acido Alendronico, Acidum Alendronicum, Alendronate, Alendronic acid
Weight 70mg, , 70mg/75ml, 10mg, 35mg, 40mg, 5mg
Type Tablet, Oral Solution, Oral Tablet, Effervescent
Formula C4H13NO7P2
Weight Average: 249.096
Monoisotopic: 249.016724799
Protein binding

78%. Studies in rats show that plasma protein binding increases with decreasing alendronic acid plasma concentration and increasing pH.

Groups Approved
Therapeutic Class Bisphosphonate preparations
Manufacturer Obs, Merck Sharp & Dohme Gesellschaft Mbh, Merck Sharp & Dohme, Lda
Available Country Pakistan, Canada, United States, Netherlands, Portugal,
Last Updated: September 19, 2023 at 7:00 am


Fosamax is used for the-

  • Treatment and prevention of osteoporosis in post-menopausal women
  • Treatment of osteoporosis, Fosamax increases bone mass and reduces the incidence of fractures, including those of the hip and spine (vertebral compression fractures)
  • Prevention of osteoporosis, Fosamax may be considered in postmenopausal women who are at risk of developing osteoporosis and for whom the desired clinical outcome is to maintain bone mass and to reduce the risk of future fracture
  • Treatment toincrease bone mass in men with osteoporosis
  • Treatment of glucocorticoid-induced osteoporosis in men and women receiving glucocorticoids in a daily dosage equivalent to 7.5 mg or greater of prednisone and who have low bone mineral density. Patients treated with glucocorticoids should receive adequate amounts of calcium and vitamin D
  • Treatment of Paget’s disease of bone in men and women

Fosamax is also used to associated treatment for these conditions: Osteogenesis Imperfecta (OI), Osteoporosis, Osteoporosis caused by glucocorticoid, Paget’s Disease

How Fosamax works

Fosamax binds to bone hydroxyapatite. Bone resorption causes local acidification, releasing alendronic acid which is that taken into osteoclasts by fluid-phase endocytosis. Endocytic vesicles are acidified, releasing alendronic acid to the cytosol of osteoclasts where they induce apoptosis. Inhibition of osteoclasts results in decreased bone resorption which is shown through decreased urinary calcium, deoxypyridinoline and cross-linked N-telopeptidases of type I collagen.


Fosamax dosage

Treatment of osteoporosis in post-menopausal women: The recommended dose is one Fosamax 70 mg once weekly or 10 mg once daily.

Treatment to increase bone mass in men with osteoporosis:The recommended dose is one Fosamax tablet 10 mg once daily. Alternatively, one Fosamax 70 mg once weekly may be considered.

Prevention of osteoporosis in post-menopausal women: The recommended dose is 35 mg once weekly or 5 mg once daily. The safety of treatment and prevention of osteoporosis with Fosamax has been studied for up to 7 years.

Use for elderly patients: No dosage adjustment is required for elderly patients. Because in clinical study there was no evidence of age related differences in the efficacy or safety profiles of Fosamax.

Treatment of glucocorticoid-induced osteoporosis in men and women: The recommended dose is 5 mg once daily, except for post-menopausal women not receiving oestrogen, for whom the recommended dose is 10 mg once daily.

Paget’s disease of bone in men and women: The recommended treatment regimen is 40 mg once a day for six months.

Side Effects

The commonest symptomatic side effects are constipation, diarrhoea, oesophageal ulcer, flatulence, dysphagia, musculoskeletal pain, headache, rarely rash, erythema, transient decrease in serum calcium and phosphate, nausea, vomiting, peptic ulceration, hypersensitivity reactions including urticaria and angio-oedema.


In clinical studies, ≥3% of patients experience abdominal pain, acid regurgitation, constipation, diarrhea, dyspepsia, musculoskeletal pain, and nausea.

No information for treatment of overdose is available, however patients should be given milk or antacids to bind alendronic acid and vomiting should not be induced. Patients may experience hypocalcemia, hypophosphatemia, and upper gastrointestinal events..

There are currently no studies for safety and efficacy in pregnancy, though studies in pregnant rats show fetal and maternal complications at 4 times the clinical dose and pregnant rabbits do not show complications at as high as 10 times the clincal dose.

Excretion in breast milk, and therefore safety in lactation, is unknown.

Fosamax has been studied for use in pediatric patients. The oral bioavailability is similar to that in adult patients, but an increase in the portion of patients experiencing vomiting.

There is no significant difference in efficacy or safety of alendronic acid in geriatric populations, though there is potential for even greater sensitivity in patients at a further advanced age than those in the study.

Fosamax is not recommended for patients with creatinine clearance Label.


The incidence of upper gastrointestinal side effects are increased with the concomitant use of non-steroidal anti-inflammatory agents and aspirin. Absorption of Alendronate is reduced in the presence of antacids and calcium supplements.

Food Interaction

  • Administer vitamin supplements. Patients may require supplemental vitamin D.
  • Avoid multivalent ions. Calcium, antacids, and divalent ions may interfere with the absorption of this medication.
  • Take before a meal. Take 30-60 minutes before breakfast.
  • Take with a full glass of water.

Volume of Distribution


Elimination Route

Mean oral bioavailability of alendronic acid in women is 0.64% and in men is 0.59%. Bioavailability of alendronic acid decreases by up to 40% if it is taken within an hour of a meal.

Half Life

Due to alendronic acid being incorporated into the skeleton, the terminal half life is estimated to be over 10 years.



Elimination Route

Administration of radiolabeled alendronic acid results in 50% recovery in urine within 72 hours. No alendronic acid is recovered in the feces. Men excrete less alendronic acid than women, though race and advanced age do not affect elimination.

Pregnancy & Breastfeeding use

Fosamax should not be given to pregnant women or nursing mother.


Hypocalcaemia; Renal impairment; Vitamin D deficiency; Active gastrointestinal problem such as dysphagia, oesophago-duodenitis or ulcer; and Hypersensitivity to any components of the tablet.

Special Warning

Children: Not recommended.

Innovators Monograph

You find simplified version here Fosamax

Fosamax contains Alendronic acid see full prescribing information from innovator Fosamax Monograph, Fosamax MSDS, Fosamax FDA label


What is Fosamax used for?

Fosamax is a bisphosphonate medication used to treat osteoporosis and Paget's disease of bone. Taking Fosamax can help if you have, or are at risk of developing, osteoporosis. This is a condition that causes your bones to get weaker and be more likely to break.

How safe is Fosamax?

This evidence shows Fosamax to be safe and effective; it should be considered the nonhormonal therapy of choice for treating osteoporosis in postmenopausal women at risk for hip and vertebral fractures.

How does Fosamax work?

Fosamax works by slowing down the production of the cells that wear down bone (osteoclasts). This helps to improve bone strength and makes the bone less fragile.

What are the common side effects of Fosamax?

Some people may have serious side effects when taking Fosamax. These include heartburn (or heartburn that gets worse), problems or pain when swallowing, or chest pain. These may be signs of ulcers in your food pipe (oesophagus). If this happens, stop taking Fosamax and speak to a doctor.

Is Fosamax safe during pregnancy?

Fosamax should not be used during pregnancy.

Is Fosamax safe during breastfeeding?

It is not known whether Fosamax is excreted into human breast milk. Given the indication, Fosamax tablet should not be used by breast-feeding women.

Can I drink alcohol with Fosamax?

Yes, you can drink alcohol while taking Fosamax. However, drinking a lot of alcohol affects the strength of your bones and can increase your risk of breaks (fractures).

Can I drive after taking Fosamax?

Fosamax may make you feel dizzy. It can also cause blurred vision, and bone, muscle or joint pain. If this happens to you, do not drive, cycle or use any machinery or tools until the effects have worn off.

When should be taken of Fosamax?

Take Fosamax first thing in the morning, before you have anything to eat or drink and before you take any other medicines. Stay sitting or standing for 30 minutes so the medicine does not irritate your food pipe (oesophagus).

How many time can I take Fosamax daily?

The usual dose of Fosamax for adults is 70mg taken once a week. There is also a 10mg tablet you take once a day. You will usually take Fosamax once a week: as a standard tablet.

How often should Fosamax be taken?

Fosamax is taken either once daily or once per week. Follow your doctor's dosing instructions very carefully.

How long does Fosamax take to work?

Fosamax usually starts to work after 1 month.

How long does Fosamax stay in my system?

You'll usually take Fosamax long term, for at least 3 to 5 years. The longer you take the medicine, the longer the effects will last.

Who should not take Fosamax?

Fosamax should not be given to children and adolescents. You may suffer from a stomach upset, heartburn, inflammation of the gullet or stomach, muscle and stomach cramps, spasms, weakness and fits.

What happen If I stop taking Fosamax?

Once you stop taking Fosamax, the effects of the medicine will gradually wear off. Your bones may continue to benefit for up to 5 years afterwards. The longer you take the medicine, the longer the effects will last.

What happen If I missed Fosamax?

Patients should be instructed that if they miss a dose of Fosamax once weekly tablet, they should take one tablet on the morning after they remember. They should not take two tablets on the same day but should return to taking one tablet once a week, as originally scheduled on their chosen day.

What happen if I overdose on Fosamax?

Hypocalcaemia, hypophosphataemia and upper gastro-intestinal adverse events, such as upset stomach, heartburn, oesophagitis, gastritis, or ulcer, may result from oral overdosage. No specific information is available on the treatment of overdosage with Fosamax.

Will Fosamax affect my fertility?

There's no evidence to suggest that taking Fosamax will reduce fertility in either men or women.

Can Fosamax affect my kidneys?

Fosamax was found to be safe and effective for the treatment of osteoporosis in women with decreased renal function.

Can Fosamax affects my liver?

Fosamax treatment has also been considered as a potential hepatotoxic agent, as high serum liver enzyme concentrations and hepatitis have occasionally been reported in a few patients while receiving Fosamax.
*** Taking medicines without doctor's advice can cause long-term problems.