Alendronic acid

Alendronic acid is a drug that is used for the treatment of osteoporosis. The drug belongs to the group of bisphosphates, which are chemical compounds containing two attached phosphate groups. However, common medicines do not contain an acid as the name “alendronic acid” suggests, but rather its salt (monosodium salt. For this reason, the name “alendronate”, which is also a common name for medicines, is a much more appropriate term.


Alendronic acid, for example, is marketed under the trade name Fosamax ® by MSD SHARP & DOHME GMBH.

Alternative preparations

  • Fosavance®, Bonviva®, Aclasta® (each with bisphosponate)
  • Protelos® (Strontium)
  • Prolia® (antibodies)
  • Evista® (selective estrogen receptor modulator (SERM))

Mode of action

Alendronic acid or alendronate has an inhibitory effect on various proteins of the bone-destroying osteoclasts. As a result, they are prevented from resorbing the bone substance. In addition, the active ingredient is said to have an activating effect on the bone-forming osteoblasts. In summary, alendronic acid inhibits bone resorption and increases the density of the bones, thus reducing the risk of bone fractures enormously.

Fields of application

Particularly in women during and after menopause/menopause, the falling oestrogen level can lead to a reduction in bone density and osteoporosis. Alendronic acid can be used in the course of this phenomenon with a dosage of up to 10 mg per day or 70 mg per week. Experience shows that this measure increases the bone density of the women concerned and effectively reduces the risk of fractures of the vertebrae and femoral neck.

Reductions in bone density and osteoporotic diseases are not uncommon in men either. In men, hormones of the adrenal cortex, so-called steroid hormones, are usually involved in the development of osteoporosis. In these cases alendronic acid can be taken in tablet form with up to 10 mg.

Side effects of alendronic acid

The list of adverse drug reactions (in short: side effects of alendronic acid) is comparatively long. The problems caused by the intake manifest themselves particularly frequently in the gastrointestinal tract and/or in the musculature as side effects. Many patients report the occurrence of moderate to severe abdominal pain and nausea when taking alendronic acid.

In addition, swallowing and/or digestive disorders and even constipation are frequently reported. Also the occurrence of partially fluid diarrhoea and baiting is not uncommon in connection with alendronic acid therapy. In particularly severe cases even: occurred.

The upper sections of the digestive tract are particularly often affected. In the area of the esophagus, therapy with alendronic acid can promote the development of inflammatory reactions (esophagitis). It can also lead to narrowing of the oesophagus (so-called strictures) and ulcers in the mouth and throat (ulcers).

A reflux of stomach acid into the oesophagus with subsequent development of inflammatory processes in the lower section of the oesophagus (reflux esophagitis) is another side effect that should not be underestimated. In the muscular area, the administration of alendronic acid can lead to muscle spasms and moderate to severe pain. In addition, some patients report joint pain and/or bone pain.

The drug may also promote the development of headaches and lead to symptoms such as confusion and even hallucinations. Severe skin redness (so-called erythema), an increased reaction to sunlight, hives (urticaria), swelling of the skin and mucous membranes, and inflammation of the eyes are also side effects of alendronic acid. Alendronic acid is said to cause osteonecrosis, i.e. the death of the bone.

Pine necrosis is especially mentioned here. This plays an important role especially in the implantation of dental implants. – Tar stools (melena, corresponds to fresh blood in the stool)

  • Stomach Ulcers
  • Perforations (perforation of the stomach) and
  • Bleeding in the gastrointestinal tract