Tamoxifen - antiestrogen for breast cancer

Tamoxifen is an active ingredient, which was marketed for the first time under the trade name Nolvadex®, but is now also available from other manufacturers (generics). Tamoxifen blocks estrogen receptors in various tissues. The drug is mainly used to treat and block hormone-sensitive tumors, as estrogens (female sex hormones) promote the growth of certain breast and uterine tumors.

What is Tamoxifen?

Tamoxifen belongs to the subgroup of antiestrogens that block certain estrogen effects and activate others: the so-called SERM (Selective Estrogen Receptor Modulators). The advantage over other drugs is that the estrogen effect is blocked in a body area, such as the chest. At the same time, however, other estrogenic effects, such as the desired action against bone osteoporosis, are retained.

How does Tamoxifen work?

Tamoxifen is a selective anti-estrogen and thus inhibits the effect of estrogens in certain tissues, especially the mammary gland, through binding to the estrogen receptor.

Tumor cells or metastases remaining after chemotherapy and surgery are thus prevented from growing: as soon as the tumor cells or the metastases lack the estrogen effect, they can no longer or only grow diminished.

At the same time, the desired estrogen effect on the body should be preserved as far as possible: tamoxifen should protect the bone by leaving the estrogen effect undisturbed there or even supported. Thus, the desired activity of estrogens can be selectively maintained and the undesirable activity, which can cause tumor growth, suppressed.

Side effects of tamoxifen

The side effects associated with tamoxifen therapy are mainly related to the lack of or increased effects of estrogens on the organ.

Thus, the following side effects may occur after taking tamoxifen:

  • Symptoms similar to those of menopause
  • Thrombosis and embolism
  • increase in weight
  • Dry skin and mucous membranes
  • vaginal bleeding

Hot flashes, hair loss and nausea

Some of the side effects are similar to menopausal symptoms. They can manifest in the form of ascending hot flashes or dry mucous membranes.

Other climacteric effects that are similar to those of menopause include nausea, hair loss and mood swings. Thromboses and embolisms can also occur more frequently.

Weight gain as a side effect

A side effect of tamoxifen is also an increased accumulation of water in the tissue, which can manifest itself in the form of a weight gain. A frequent question of the affected patients is therefore: "What can be done against weight gain?".

Who, despite tamoxifen keep his initial weight or even want to lose weight during therapy, should therefore pay attention specifically to his diet and exercise.

This is also important because during tamoxifen therapy in addition to weight gain and the blood lipid levels (triglycerides) may be increased. This in turn is bad for the heart and vessels and can also be diminished by exercise and a balanced diet.

To monitor blood lipids, regular blood count tests should be performed under tamoxifen therapy.

Side effects: bleeding and dry mucous membranes

As mentioned, tamoxifen can cause dry skin and mucous membranes. Therefore, on the one hand, there can often be harmless vaginal bleeding during therapy. On the other hand, bleeding can be an indication of a malignant process of the uterus, which can still be stimulated by the estrogen effect of tamoxifen.

Therefore, bleeding on tamoxifen therapy in postmenopausal women or menopausal bleeding should always be studied.

For more details on side effects, see the package insert and ask your doctor or pharmacist.

Interactions of tamoxifen

Concomitant use of antidepressants such as fluoxetine or paroxetine may result in decreased tamoxifen activity.

Application of tamoxifen

Tamoxifen is often prescribed for long-term treatment of breast cancer and taken daily for several years. The normal dosage is between 20 and 40 mg a day, usually tamoxifen 20 mg is sufficient.

When using tamoxifen, it should be noted that the drug may be discontinued after a certain period of time (two to five years, depending on the study) and replaced with another to avoid tumor cell resistance. This, as well as discontinuation of tamoxifen, should be discussed with the attending physician.

Another area in which the use of tamoxifen is considered is the treatment of gynecomastia - benign enlargement and swelling of the male breast. Gynecomastia is more common among athletes and bodybuilders, which is why athletes are also discussing the off-label use of tamoxifen.

How much does Tamoxifen cost?

You can buy tamoxifen in the pharmacy, the price depends on the manufacturer and the costs are covered in Germany up to the fixed amount limit by the health insurance. It should be noted that tamoxifen is a prescription.

Alternatives to tamoxifen

Clomiphene or clomiphene citrate (Clomid), like tamoxifen, belongs to the group of antiestrogens. Clomiphene is usually not used in the treatment of breast cancer, but in children and fertility problems.

In the post-treatment of breast cancer, in contrast to the anti-estrogens, there is another important group of drugs: the aromatase inhibitors, such as anastrazole (Arimidex®) or exemestane (Aromasin®). Post-treatment of breast cancer may also take the form of a combination of tamoxifen and aromatase inhibitors, for example by discontinuing tamoxifen after two years and then continuing the therapy with aromatase inhibitors.

Another active ingredient also used in the treatment of breast cancer is trastuzumab (Herceptin®). Herceptin® works in another way, it blocks the HER2 receptor, which is only found on some types of cancer on the cells. In contrast to the aromatase inhibitors, it can also be taken in addition to tamoxifen.

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