Tamoxifen-Eigenschaften Tamoxifen properties

Tamoxifen Properties – what you absolutely need to know!

Tamoxifen properties derive from many properties, whether they are always good will be discussed in this article. It is a drug mainly used to treat breast cancer in women. It acts as a selective estrogen receptor modulator (SERM), which either inhibits or promotes the effect of estrogen depending on the tissue. Tamoxifen was developed in the 1970s by ICI Pharmaceuticals (now AstraZeneca) and has been approved in Germany since 1985.

Tamoxifen Eigenschaften
Tamoxifen Properties

Structural formula of tamoxifen

What does Tamoxifen do in the Body?

Tamoxifen binds to estrogen receptors in various cells and tissues. Depending on the tissue, it can have different effects:

  • In breast tissue, tamoxifen acts as an antagonist, meaning it displaces the body’s own estrogen from the receptors and thus prevents its stimulating effect on cell growth. This can inhibit or stop the growth of hormone-dependent breast tumors.
  • In the uterus, bones, and fat metabolism, tamoxifen acts as an agonist, meaning it activates the estrogen receptors and thus has a similar effect to the body’s own estrogen. This can have positive effects on bone density, blood lipids, and the cardiovascular system.

Can I Even Convert Tamoxifen?

To understand tamoxifen’s properties, one must know that it is converted into several metabolites by various enzymes of the cytochrome P450 system (CYP) in the liver. One of these metabolites is endoxifen, which has an even higher affinity for estrogen receptors than tamoxifen itself. The conversion of tamoxifen to endoxifen varies individually and can be influenced by genetic factors or interactions with other drugs. The concentration of endoxifen in the blood can therefore be an important factor for the effectiveness of tamoxifen.

7-10% of women cannot produce enough endoxifen. There are genetic tests to determine whether a patient can convert tamoxifen into the 100x more effective endoxifen.

How is Tamoxifen used?

Tamoxifen is taken in tablet form. The usual dosage is 20 to 40 mg per day. The duration of therapy depends on the stage and type of breast cancer as well as the response to treatment. Tamoxifen is usually taken for at least five years.

What happens after 5 years of Tamoxifen?

Often tamoxifen is stopped after 5 years as standard, although the doctor does not know if it is safe. Studies have shown that taking it for 10 years leads to fewer recurrences (recurring tumors). However, there is the maintrac method that can relatively well determine whether new tumor activity is expected.

Further Tamoxifen Properties when used

Tamoxifen can be used both as adjuvant therapy after surgery or radiation therapy and as palliative therapy for advanced or metastatic breast cancer. Tamoxifen can also be used to prevent breast cancer in women at increased risk.

To maintain the active level, tamoxifen should always be taken at the same time of day if possible. The tablets can be taken with or without food. The intake should not be stopped or interrupted without consulting a doctor.

What are the Side Effects of Tamoxifen?

amoxifen can have various side effects that can vary in severity depending on the patient. The most common side effects include:

  • Hot flashes
  • Sweating
  • Nausea
  • Vomiting
  • Weight gain
  • Fatigue
  • Headache
  • Dizziness
  • Depression
  • Mood swings
  • Sleep disorders
  • Hair loss
  • Rash
  • Itching
  • Vision problems

The serious side effects include:

  • Thrombosis
  • Embolism
  • Stroke
  • Heart attack
  • Uterine cancer
  • Liver damage

Not all side effects occur in every patient. If side effects occur, the doctor should be informed in order to adjust the dose or change the therapy if necessary.

What Should be Considered When Taking Tamoxifen?

Tamoxifen should only be taken on a doctor’s prescription and under regular control. The following points should be observed:

  • Tamoxifen is contraindicated in case of hypersensitivity to the active substance, during pregnancy and breastfeeding, in case of severe liver dysfunction and during concomitant therapy with an aromatase inhibitor.
  • It can affect the effect of other drugs or be affected by them. These include, for example, anticoagulants, antidepressants, anticonvulsants, antibiotics, antifungals, antiretrovirals, grapefruit juice and St. John’s wort. Before taking tamoxifen, the doctor should be informed about all other drugs taken.
  • Tamoxifen can impair fertility and lead to menstrual disorders or absence of menstruation. During therapy with tamoxifen, a reliable method of contraception should be used as pregnancy increases the risk of miscarriage or malformations. After discontinuation of tamoxifen, fertility can be restored.
  • Tamoxifen can increase the risk of uterine cancer. Therefore, regular gynecological examinations should be performed. If unusual bleeding, pain or pressure in the lower abdomen occurs, a doctor should be consulted.
  • It can increase the risk of thrombosis or embolism. Therefore, risk factors such as smoking, obesity or lack of exercise should be avoided. If pain or swelling in the legs, shortness of breath, chest pain or vision problems occur, a doctor should be consulted immediately.
  • Tamoxifen can increase bone density and thus protect against osteoporosis. Nevertheless, an adequate intake of calcium and vitamin D should be ensured. Regular physical activity can also promote bone health.

How Much does Tamoxifen Cost?

Tamoxifen is a prescription drug available in various package sizes and dosages. The cost for a one-month pack with 20 mg tablets varies between 10 and 20 euros depending on the manufacturer. The cost of therapy with tamoxifen is usually covered by statutory health insurance

What Significance does Maintrac play in Connection with the properties of Tamoxifen

With maintrac it is possible to control the circulating tumor cell count before, during and after therapy. It should ideally remain stable or even decrease over the years.

However, if the cell count increases significantly during or shortly after discontinuation of therapy (>factor 3), it is necessary to discuss a change or resumption of tamoxifen therapy with the doctor.

In case of constant cell count after end of tamoxifen therapy a half-yearly monitoring is recommended to detect new tumor activity early.

Recommendation for monitoring tamoxifen therapy


Tamoxifen is an effective drug for the treatment of breast cancer in women. It acts as a selective estrogen receptor modulator that either inhibits or promotes the effect of estrogen depending on the tissue. Tamoxifen is converted into endoxifen in the liver, which has an even higher affinity (x100) for estrogen receptors. It is taken in tablet form and has a manageable but sometimes unpleasant side effect profile. Tamoxifen should only be taken on a doctor’s prescription and under regular control. Ideally, tamoxifen properties are accompanied by regular cell counts.

Please note that this article is for informational purposes only and does not replace consultation or treatment by a doctor.

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