Alendronic acid

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The active ingredient alendronic acid belongs to the group of bisphosphonates and is used to treat osteoporosis and other diseases that lead to bone loss. Alendronic acid is used in medicinal products as the sodium salt (sodium alendronate), which is more soluble. Here you can read more about the effects and use of alendronic acid, side effects and other important information.

This is how alendronic acid works

Human bone is subject to constant remodeling by specialized cells - osteoclasts and osteoblasts. The osteoclasts (from the Greek "bone breaker") break down bone substance, both the connective tissue and the mineral part of the bones (mainly consisting of calcium phosphate). The osteoblasts ("bone pictures") build up new bone substance. This process of building up and breaking down is mostly in equilibrium (so-called homeostasis), so that the overall bone mass and stability are retained.

However, the balance can be disturbed by various external and internal circumstances, with an increased breakdown leading to diseases such as osteoporosis. This can be triggered by increased thyroid and parathyroid hormone levels and low estrogen levels (e.g. after the menopause).

Bisphosphonates such as alendronic acid can be used to specifically influence the cells involved in bone remodeling. The alendronic acid acts primarily on the osteoclasts and ensures that they are less active and have a shorter life and therefore duration of action. Although alendronic acid also has a harmful effect on osteoblasts, the effect on osteoclasts predominates, whereby the disturbed balance of bone remodeling can be restored.

Uptake and excretion of alendronic acid

After ingestion by mouth, the active ingredient is only very slightly absorbed into the blood through the intestinal wall. About half of the active ingredient reaches the bones from the blood and is bound there. The other half of the alendronic acid is excreted unchanged via the kidneys with the urine within one day. The active substance bound in the bone is only released very slowly (around half in ten years).

When is alendronic acid used?

Alendronic acid is mainly used for the treatment of postmenopausal osteoporosis, i.e. in women with osteoporosis after the menopause. However, it can also be given preventively here. In men, alendronic acid is only approved for existing osteoporosis, i.e. not for prevention.

In addition, alendronic acid is approved for the treatment of forms of osteoporosis caused by the use of medication. Osteoporosis often occurs as a side effect, particularly with glucocorticoid therapy ("cortisone therapy") for chronic inflammatory diseases.

For the treatment of other diseases such as Paget's disease (osteodystrophia deformans) and glass bone disease (osteogenesis imperfecta), alendronic acid is used “off-label”, ie without approval.

Alendronic acid is usually taken for several years.

This is how alendronic acid is used

The active ingredient alendronic acid is taken in the form of tablets or soft capsules once a day in the morning on an empty stomach. Alendronic acid is very poorly absorbed by the intestine into the blood (only about 0.6 to 0.7 percent of the dose taken). The timely consumption of food or drinks would worsen the absorption even further, which is why the active ingredient must be taken at least half an hour before breakfast. No juice or coffee should be drunk when swallowing the tablets, only water.

Before starting therapy, the calcium blood level should be determined and, if necessary, evened out, as alendronic acid can further reduce it. Calcium tablets and vitamin D3 (often in combination with alendronic acid in soft capsules) are usually prescribed as additional therapy.

Some patients do not tolerate alendronic acid tablets well - symptoms such as nausea and abdominal pain occur. Instead of the usual daily intake of ten milligrams of alendronic acid, you can then switch to a once-weekly dose of 70 milligrams.

As with other bisphosphonates, preparations for injection are not available for alendronic acid.

What side effects does alendronic acid have?

Typically, alendronic acid is well tolerated.

More than ten percent of patients experience bone, muscle, or joint pain.

Alendronic acid side effects such as headache, dizziness, weakness, abdominal pain, indigestion, diarrhea, heartburn, ulcers of the esophagus (especially if the tablets are not swallowed with sufficient fluid), bloated stomach, itching, Hair loss, joint swelling and water retention in the tissue.

By taking alendronic acid once a week, some side effects can be mitigated compared to the daily intake.

What should be considered when taking alendronic acid?

Intestinal absorption poses the greatest risk of interactions with other drugs, dietary supplements, and food. Alendronic acid should be taken completely separately from other active ingredients and foods, as otherwise absorption will be significantly inhibited. Especially with calcium, insoluble compounds are formed in the stomach and intestines that are not absorbed.

Alendronic acid has an irritating effect on the mucous membranes, especially if the tablets are not taken with sufficient tap water. Simultaneous use of non-steroidal anti-inflammatory drugs, which are often taken as pain relievers (such as ASA, ibuprofen and diclofenac), can increase the irritation of the gastric mucosa.

Factors such as poor oral hygiene, dental disease, periodontal disease, smoking, and cancers that are treated with chemotherapy can increase the risk of alendronic acid developing jawbone necrosis (tissue death). In case of doubt, an examination by the dentist should be carried out before starting therapy. Orthodontic treatments and operations (such as the placement of implants) should not be performed during bisphosphonate therapy.

Alendronic acid should not be used during pregnancy and breastfeeding as there are limited studies on it. It is not known whether the active substance is excreted in breast milk.

The efficacy and safety of therapy with alendronic acid in children and adolescents has not been established and it should therefore not be used in these patients. In older age, therapy is possible without restrictions, but should not be used in the case of severe kidney dysfunction.

How to get medicines with alendronic acid

Preparations with the active ingredient alendronic acid (also in combination with vitamin D3) require a prescription and can be purchased from pharmacies with a prescription.

How long has alendronic acid been known?

Bisphosphonates were first chemically produced in Germany in 1865. However, it was only used technically and industrially, for example for water softening. The effect on living organisms, especially the effect on bone metabolism, was not investigated until the 1960s. Around 30 years later, in the 1990s, the mechanism of action that is still accepted today was deciphered and alendronic acid was approved in Germany in 1996 by the pharmaceutical company MSD - Merck Sharp & Dohme, Inc. Since 2005 there have been numerous generics with the active ingredient alendronic acid on the German market.

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