What are the side effects of Alendronate (Fosamax)?

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From the Guidelines

Alendronate can cause several side effects, including gastrointestinal issues, musculoskeletal pain, and rare but serious conditions such as esophageal ulcers, osteonecrosis of the jaw, and atypical femur fractures, as reported in high-quality evidence studies 1.

Common Side Effects

  • Gastrointestinal issues such as heartburn, stomach pain, nausea, and acid reflux
  • Musculoskeletal pain, particularly in the bones, joints, or muscles
  • Headaches and dizziness

Rare but Serious Side Effects

  • Esophageal ulcers
  • Osteonecrosis of the jaw (death of jawbone tissue)
  • Atypical femur fractures with long-term use

Minimizing Gastrointestinal Side Effects

To minimize gastrointestinal side effects, patients should take alendronate with a full glass of water first thing in the morning, remain upright for at least 30 minutes after taking it, and avoid eating or drinking anything else during this time, as recommended by studies 1.

Monitoring and Reporting Side Effects

Patients should report persistent or severe side effects to their healthcare provider immediately, as dosage adjustments or alternative treatments may be necessary, and regular dental check-ups are also important while taking alendronate to monitor jaw health 1.

Evidence-Based Recommendations

The most recent and highest quality study 1 provides evidence-based recommendations for the management of osteoporosis, including the use of alendronate, and highlights the importance of weighing the benefits and risks of treatment, particularly with regards to rare but serious side effects.

From the FDA Drug Label

Alendronate sodium tablets, USP can cause serious side effects including: Esophagus problems Low calcium levels in your blood (hypocalcemia) Bone, joint, or muscle pain Severe jaw bone problems (osteonecrosis) Unusual thigh bone fractures The most common side effects of alendronate sodium tablets, USP are: Stomach area (abdominal) pain Heartburn Constipation Diarrhea Upset stomach Pain in your bones, joints, or muscles Nausea

The side effects of alendronate include:

  • Serious side effects:
    • Esophagus problems
    • Low calcium levels in the blood (hypocalcemia)
    • Bone, joint, or muscle pain
    • Severe jaw bone problems (osteonecrosis)
    • Unusual thigh bone fractures
  • Common side effects:
    • Stomach area (abdominal) pain
    • Heartburn
    • Constipation
    • Diarrhea
    • Upset stomach
    • Pain in bones, joints, or muscles
    • Nausea 2 2

From the Research

Side Effects of Alendronate

  • The most common side effects of alendronate include abdominal pain, nausea, dyspepsia, acid regurgitation, and musculoskeletal pain, which are often transient and associated with the upper GI tract 3.
  • Postmarketing surveillance has reported a low incidence of adverse events related to the oesophagus 3.
  • Upper GI tract adverse events can be reduced by following specific instructions provided by the manufacturer, such as taking the medication with a full glass of water and remaining upright for at least 30 minutes after taking the medication.
  • Other potential side effects of alendronate include:
    • Osteonecrosis of the jaw (ONJ) 4
    • Atypical femur fractures 4
    • Upper gastrointestinal side effects, such as esophagitis and gastritis 4
    • Acute phase reactions, which can occur with intravenous bisphosphonates 4

Reducing Side Effects

  • New formulations and dosages of alendronate, such as once-weekly dosing, have been developed to reduce the risk of upper GI adverse events and improve adherence to treatment 5.
  • Combining alendronate with vitamin D may also help to reduce the impact of gastro-oesophageal adverse events 5.
  • Patients should be instructed on how to take alendronate properly to minimize the risk of side effects, including taking the medication with a full glass of water and remaining upright for at least 30 minutes after taking the medication 3.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Benefits and risks of bisphosphonate therapy for osteoporosis.

The Journal of clinical endocrinology and metabolism, 2012

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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