Tamoxifen is an active ingredient that was first marketed under the trade name Nolvadex, but is now available from other manufacturers (generics). Tamoxifen blocks estrogen receptors in various tissues. The drug is used primarily to treat and block hormone-sensitive tumors because 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: called SERMs (selective estrogen receptor modulators). The advantage over other agents is that the estrogen effect is blocked in one area of the body, such as the breast. At the same time, however, other estrogen effects, such as the desired effect against osteoporosis in the bone, are retained.
How does tamoxifen work?
Tamoxifen is a selective antiestrogen and thus inhibits the effects of estrogens in certain tissues, especially the mammary gland, by binding to the estrogen receptor. After chemotherapy and surgery, any remaining tumor cells or metastases are prevented from growing in this way: As soon as the tumor cells or metastases lack the estrogen effect, they can no longer grow or can only grow at a reduced rate. At the same time, the desired estrogen effect on the body is to be preserved as far as possible: Tamoxifen is intended to protect the bone by leaving the estrogen effect there unimpaired or even supporting it. In this way, the desirable activity of estrogens can be selectively maintained and the undesirable activity that can cause tumor growth can be suppressed.
Side effects of tamoxifen
The side effects that may occur during therapy with tamoxifen are mainly related to the lack of or increased effect of estrogens on the organ in question. Thus, the following side effects may occur after taking tamoxifen:
- Complaints similar to those of menopause
- Thromboses and embolisms
- Weight gain
- Dry skin as well as mucous membranes
- Vaginal bleeding
Hot flashes, hair loss and nausea.
Some of the side effects are similar to the symptoms experienced during menopause. They may take the form of rising hot flashes or dry mucous membranes. Other menopausal-like effects include nausea, hair loss, and mood swings. Thromboses and embolisms may also occur more frequently.
Weight gain as a side effect
A side effect of tamoxifen is also an increased accumulation of water in the tissues, which can take the form of weight gain. Therefore, a common question asked by affected patients is, “What can be done about weight gain?” Anyone who wants to maintain their initial weight despite tamoxifen or even lose weight during therapy should therefore pay targeted attention to their diet and exercise. This is also important because, in addition to weight gain, blood fat levels (triglycerides) can also be elevated during tamoxifen therapy. This in turn is bad for the heart and blood vessels and can also be reduced by exercise and a balanced diet. To monitor blood lipids, regular blood count checks should be performed during tamoxifen therapy.
Side effects: Bleeding and dry mucous membranes
Tamoxifen can cause dry skin and mucous membranes, as mentioned. Therefore, on the one hand, harmless vaginal bleeding may occur more frequently during therapy. On the other hand, bleeding may also be an indication of a malignant process in the uterus, which may be further stimulated by the estrogen effect of tamoxifen. Bleeding during tamoxifen therapy in postmenopausal women or bleeding irregularities before menopause must therefore always be investigated. For more details on side effects, see the package insert and ask your treating physician or pharmacist.
Tamoxifen interactions
Taking antidepressants such as fluoxetine or paroxetine at the same time may result in a decreased effect of tamoxifen.
Use of Tamoxifen
Tamoxifen is often prescribed for long-term treatment of breast cancer and is 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 can be discontinued after a certain period of time (two to five years, depending on the study) and replaced by another one in order to avoid resistance of the tumor cells. This, as well as discontinuation of tamoxifen, should be discussed with the treating physician. Another area where the use of tamoxifen is being considered is in the treatment of gynecomastia – benign enlargement and swelling of the male breast. Gynecomastia is clustered in athletes and bodybuilders, among others, so off-label use of tamoxifen is also being discussed in athletic circles.
How much does tamoxifen cost?
You can buy Tamoxifen at the pharmacy, the price depends on the manufacturer and the costs are covered by health insurance in Germany up to the fixed amount limit. It should be noted that Tamoxifen is available only on prescription.
Alternatives to tamoxifen
Clomiphene or clomiphene citrate (Clomid) belongs to the group of antiestrogens, as does tamoxifen. However, clomiphene is not usually used in the treatment of breast cancer, but is used to treat infertility and fertility problems. In the post-treatment of breast cancer, on the other hand, there is another important group of drugs in addition to the antiestrogens: the aromatase inhibitors, such as anastrazole (Arimidex) or exemestane (Aromasin). Post-treatment of breast cancer can also take the form of a combination of tamoxifen and aromatase inhibitors, for example by discontinuing tamoxifen after two years and then continuing therapy with aromatase inhibitors. Another agent that is also used in the treatment of breast cancer is trastuzumab (Herceptin). Herceptin works by a different pathway, blocking the HER2 receptor, but this is only found on cells in some forms of cancer. It can also be taken in addition to tamoxifen, unlike the aromatase inhibitors.
