Fields of application (indications)
Tamoxifen as an antiestrogen is used as a supportive long-term therapy for at least five years after the initial treatment of breast cancer (mammary carcinoma). In addition, it is also used in the treatment of metastatic breast cancer. One speaks of a metastasized breast carcinoma if the breast cancer has already caused daughter tumors, so-called metastases.
Tamoxifen therapy is only effective if estrogen receptors have been detected in the tumor tissue. The presence of estrogen receptors can be determined by a pathologist using a tissue sample obtained during a biopsy or surgery. The clinical use of tamoxifen has been shown to improve blood lipid levels in postmenopausal women.
A reduction in total cholesterol and LDL of 10-20% has been shown.In addition, preservation of bone density in postmenopausal women was also noted. Normally, there is a decrease in bone density in menopausal women. In the United States of America, tamoxifen has also been approved for the prevention of breast cancer in high-risk patients.
Contraindication
Tamoxifen must not be used in the case of known hypersensitivity to the active ingredient Tamoxifen or any of the other ingredients. In addition, Tamoxifen is not intended for use during pregnancy, while breast-feeding or in children and adolescents under 18 years of age.
Adverse drug reactions
Adverse drug reactions caused by tamoxifen are largely explained by its effect on the hormone system. Hot flushes, discharge and cycle disturbances up to the complete absence of monthly menstruation before the actual menopause are very often complained about when taking Tamoxifen. Pruritus (itching) in the genital area and bleeding from the vagina are frequently reported.
Benign and malignant changes in the uterus and the lining of the uterus can also occur frequently. The incidence of malignant changes in the lining of the uterus (endometrial carcinoma) is increased by a factor of 2 to 4 in women taking tamoxifen compared to women without tamoxifen treatment. Occasionally, especially in the case of bone tumors and/or a calcium-rich diet, an increase in the blood calcium level may occur (hypercalcemia).
Rare, however, are cysts on the ovaries (ovarian cysts) and malignant tumors of the uterus itself (uterine sarcomas). Pain in the area of the diseased tissue as well as bone pain often occur at the beginning of therapy. Taking tamoxifen can cause some undesirable drug effects in the area of the eyes.
These include corneal and retinal changes (retinopathies) or clouding of the lens of the eye, also known as cataract. In addition, inflammation of the optic nerve can be caused by therapy with tamoxifen (optic neuritis), which in rare cases can cause blindness. Due to the possible ophthalmological side effects described above, regular ophthalmological check-ups are recommended when treating with tamoxifen.
Normally, this checkup should be performed every one to two years. Patients often complain of headaches and drowsiness. Very rarely, pneumonia, a so-called interstitial pneumonitis, may occur.
Occasionally there are deviations in liver enzyme values, which can be determined by taking a blood sample. The development of fatty liver (steatosis hepatis), inflammation of the liver (hepatitis) or impaired bile flow are also rarely reported. An increase in certain blood lipids (serum triglycerides) is frequently reported.
Very rarely this can be so pronounced that an increase in serum triglycerides can lead to inflammation of the pancreas (pancreatitis). Patients often complain of nausea when taking tamoxifen. Occasionally vomiting may also occur.
Treatment with tamoxifen often causes temporary anaemia. The decrease in other groups of blood cells, such as white blood cells (leukopenia) or platelets (thrombocytopenia) is occasionally reported. Serious changes in the blood count are very rare, however.
With regard to the vascular system, blood clots can form in veins (thrombosis, embolism), for example in the leg (deep vein thrombosis) and subsequently also in the lungs (pulmonary embolism). The incidence of these so-called thromboembolic complications is increased with simultaneous chemotherapy. A stroke (apoplexy) can also occur under therapy with tamoxifen.
The use of tamoxifen has been reported to lead to an increased incidence of skin rashes and hair loss. Occasionally there are hypersensitivity reactions, which can be accompanied by swelling of tissues (so-called angioneurotic edema). If you experience any of the adverse drug reactions described above, inform your doctor so that he or she can decide how to proceed.
Adverse drug reactions that have not yet been described should also be reported to the attending physician. Before you start therapy with the selective estrogen receptor modulator (SERM) Tamoxifen, you should inform the attending physician about other medications you are taking.It is important that you do not ignore non-prescription drugs. The efficacy of tamoxifen can be diminished by numerous drugs used for depression (antidepressants).
These include antidepressants from the group of selective serotonin reuptake inhibitors, such as fluoxetine and paroxetine, the selective dopamine and norepinephrine reuptake inhibitor bupropion, but also the antiarrhythmic drug quinidine and the active substance cinacalcet. The reason for this is a conversion of tamoxifen into the active substance endoxifen by an enzyme from the cytochrome P450 enzyme system called CYP2D6, which can be inhibited by the above-mentioned preparations. Other drugs may increase the effect of tamoxifen, which also increases the risk of adverse drug reactions.
The degradation of tamoxifen via the enzyme CYP3A4 may also play a role in interactions with other drugs. For example, an inducer of CYP3A4, such as the antibiotic rifampicin, can accelerate the degradation of tamoxifen and thus lower the plasma level of tamoxifen. This mechanism could therefore also cause a reduction in the effectiveness of tamoxifen.
Among the drugs that cause the effect to be intensified are anticoagulants. Chemotherapy while taking Tamoxifen increases the risk of blood clots forming (thromboembolic events). As a so-called selective estrogen receptor modulator (SERM), Tamoxifen may have an effect mainly on the action of other hormone preparations. In particular, preparations containing estrogens can lead to a mutual attenuation of effect when taken together with tamoxifen.
