Fosamax Side Effects

Fosamax side effects and drug information

Fosamax functions by slowing down the process of bone loss, and at the same time reduce the risk of having fractured bones. This medication also helps in keeping strong bones.  

Bioavailability 0.6%
ChemSpider ID 2004
PubChem CID 2088
ChemSpider ID 2004
CAS ID 121268-17-5



It comes with a generic name called Alendronate, which belongs to the classification of drugs called bisphosphonates. The purpose of this medication is to treat some types of bone loss among adults and also Paget’s disease. Aside from treatment, Fosamax prevents bone loss from actually happening as well.  

More than these effects, Fosamax is also being studied for other possible treatments such as for hypercalcemia, which involves having high levels of calcium in the blood, and for bone and chest pain that is caused by cancer.

This medication is available in three types of dosage forms which are: solution, tablet, and tablet effervescent, and is only available upon doctor’s prescription.

Side Effects

Fosamax, which is a bisphosphonate, is used to prevent as well as treat Paget’s disease and osteoporosis. It is also available in a generic form called alendronate sodium. Though this medication works to treat and prevent bone loss, it may come with some side effects, both common and severe.

Common side effects

Severe potential side effects

  • Swelling of the face, throat or tongue
  • Eye pain
  • Chest pain
  • Difficulty in swallowing
  • Bloody stools
  • Skin blisters
  • Severe pain in either the joints, bone, muscle, back or jaw
  • Heartburn

Indication and dosage

Though the generic form of Fosamax is Alendronate, they are no longer marketed in the same way, such that Alendronate is still available in various dosages, which are: 5mg, 10 mg, 35mg, and 40 mg. Fosamax is not available in varying degrees.

Also, while generic form Alendronate is still available in oral solution, Fosamax is not.

Treatment of Osteoporosis in Postmenopausal Women

Fosamax can be taken in three different dosages:

  • (1) 70mg of Fosamax tablet once every week, or
  • (1) bottle of 70mg oral solution once every week, or
  • (1) 10mg tablet once a day.

Prevention of Osteoporosis in Postmenopausal Women

The acceptable dosage for osteoporosis prevention in postmenopausal women would be:

  • (1) 35mg of Fosamax tablet once a week, or
  • (1) 5mg tablet once every day

Treatment to Increase Bone Mass in Men with Osteoporosis

For this kind of treatment, the recommended dose is:

  • (1) 70mg Fosamax tablet once every week, or
  • (1) bottle of 70mg oral solution once every week, or
  • (1) 10mg tablet once a day

Treatment of Glucocorticoid-Induced Osteoporosis

The right amount of dosage for this treatment is generally 5mg of Fosamax tablet once each day. Still, for postmenopausal women who are not receiving estrogen, the dosage would be 10mg tablet once a day.

Treatment of Paget’s Disease of Bone

The dosage recommended is 40mg once daily for six months.

Retreatment of Paget’s Disease

A treatment with Fosamax is possible and may be reconsidered depending on the situation of the patient. It is likely for those whose serum alkaline phosphatase failed to become normal, or it can also be retaken after a six-month post-evaluation period of patients who have relapsed.  

Individuals with Paget’s disease’s serum alkaline phosphatase should be checked periodically.

Important Administration Instructions

Essential notes for patients who are taking Fosamax:

  • This medication must be taken on an empty stomach pain and should be taken at least 30 minutes (and not anything less than 30) before the first food, beverage, or other medicines of the day. Recommended drink is only plain water as mineral water, or different types of drinks would decrease its absorption. 
  • To minimize or prevent esophageal irritation, Fosamax should be taken upon arising for the day, and not before bedtime or before arising for the day. It should be taken with a full glass of water, which is 6 to 8 ounces. As for gastric emptying, after taking Fosamax oral solution, at least 2 ounces of water should come right after. Those who are taking this medication are advised not to lie down for a minimum of 30 minutes and not until after their first food of the day.

Recommendations for Calcium and Vitamin D Supplementation

If an individual’s dietary intake is not enough, then they should be asked to take supplemental calcium. People who are above 70 years old, or are chronically ill, or living in a nursing home may need a supplement of Vitamin D as they may have a risk for Vitamin D insufficiency. Other types of people who may need a higher dose of Vitamin D are those with gastrointestinal malabsorption syndrome.

Those who have been treated with glucocorticoids are advised to receive the proper amount of Vitamin D and calcium.

Administration Instruction for Missed Doses

In case of a missed intake for a once a week dosage, Fosamax should not be taken twice on the same day. Instead, still, take one dose after you remember then follow the dosage as initially scheduled.

Drug Interaction

Calcium Supplements/ Antacids

Absorption of Fosamax may interfere with antacids, calcium, or other oral medications that have multivalent cations. It is advised that you wait for a minimum of 30 minutes before having any other oral medicines.


Aspirin- containing medicines along with everyday doses of more than 10mg of Fosamax and those receiving concomitant therapy have reported upper gastrointestinal adverse effects.

Nonsteroidal Anti- Inflammatory Drugs

Although Fosamax may be taken with NSAIDs, there could be upper gastrointestinal adverse effects that may potentially occur.  

Warnings and Precautions

Upper Gastrointestinal Adverse Reactions

Because bisphosphonates are known to irritate the upper gastrointestinal mucosa, Fosamax should be given with much care to individuals who have ongoing digestive concerns like gastritis, ulcers, duodenitis, other esophageal diseases, Barrett’s esophagus or dysphagia.

Esophageal adverse reactions like esophageal erosions, ulcers, and esophagitis that are sometimes accompanied by bleeding but rarely followed by esophageal perforation are known to be experienced by individuals taking Fosamax and other oral bisphosphonates.  

If any symptoms related to esophageal reactions arise, you must consult with your doctor, and Fosamax discontinued. You need to seek urgent medical attention if you experience the following symptoms: worsening heartburn, dysphagia, odynophagia, or retrosternal pain.

Severe esophageal adverse reactions are reported to be highly experienced by patients who lie down after taking the medication, or those who are not able to swallow the medicine completely or without taking it with the recommended full glass of water.  

Because Fosamax may cause some side effects, taking this medication with the specific dosage recommendation is essential.  

For those who have incapacities to follow dosing instructions, appropriate supervision for Fosamax intake is highly recommended.  

Mineral Metabolism

Patients who have disorders that are related to mineral metabolisms like vitamin D deficiency or hypocalcemia should first be treated for these conditions before starting their Fosamax treatment.  

For individuals with this kind of condition, signs of hypocalcemia and their levels of calcium need to be checked continuously while in treatment for Fosamax.  

Musculoskeletal Pain

Patients who have taken Fosamax or other products with bisphosphonates have had experiences of pain in the muscle, joint, and bone, both occasional and severe. Most patients who have treatment with this were postmenopausal women, and the onset of the symptoms was different from each individual.  

As soon as the symptoms appear, stop using the medication. Those who discontinued its use after developing symptoms had experienced relief.  

Osteonecrosis of the Jaw

ONJ occurs due to tooth extraction, or local infection with delayed healing. This condition reportedly happens in patients who are taking Fosamax and other bisphosphonates.  

The risk factors for osteonecrosis of the jaw are dental implants, tooth extraction, diagnosis of cancer, chemotherapy, corticosteroids, poor oral hygiene, anemia, dental disease, and the like. The risk becomes higher as long as there is exposure to bisphosphonates.

Atypical Subtrochanteric and Diaphyseal Femoral Fractures

Individuals who have had exposure or have been treated with bisphosphonates are known to have atypical fractures or low trauma fractures in the femoral shaft. Those who exhibit pain in the thigh or groin are suspected of having this type of fracture and must check for an incomplete femur fracture. Patients with an atypical fracture should be monitored for symptoms of fracture in the contralateral limb as well.

Renal Impairment

This medication should not be taken by individuals with a creatinine clearance of less than 35mL/ min.

Glucocorticoid-Induced Osteoporosis

At the onset of Fosamax treatment, a bone mineral density measurement should be made and must repeat after 6 to 12 months of combined treatments of glucocorticoid and Fosamax.

But before starting Fosamax treatment, the gonadal hormonal status of men and women must first be assessed and replaced if needed.

Clinical Pharmacology

Alendronate, which is the generic form of Fosamax, is a treatment or prevention for osteoporosis and is said to be an effective and safe treatment as it does not promote bone calcification or influence healing of fracture in chronic administration.  

The main risk in having osteoporosis is the development of fractures, but the efficacy of Alendronate is said to inhibit fractures and is reported in Japan.  

Alendronate is a type of nitrogen that contains bisphosphonate, and binds with the bone surface and lessen osteoclast-mediated bone resorption.

It is an active agent to treat osteoporosis in more than 90 countries and is used by over 4.5 million individuals.

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