In Treatment of:
Tamoxifen is currently used for the treatment of both early and advanced ER+ (estrogen receptor positive) breast cancer in pre- and post-menopausal women. Additionally, it is the most common hormone treatment for male breast cancer. It is also approved by the FDA for the prevention of breast cancer in women at high risk of developing the disease. It has been further approved for the reduction of contralateral (in the opposite breast) cancer.
In McCune-Albright syndrome (MAS) tamoxifen has been used to treat premature puberty and the consequences of premature puberty. Tamoxifen has been seen to decrease rapid bone maturation which is the result of excessive estrogen and alter predicted adult height (PAH). The same effects have also been seen in short pubertal boys.
However, one in vitro study in 2007 and later an in vivo study in 2008 have shown that tamoxifen induces apoptosis in growth plate chondrocytes, reduces serum IGF-I levels and causes persistent retardation of longitudinal and cortical radial bone growth in young male rats, leading the researches to express concern giving tamoxifen to growing individuals.
Tamoxifen is used to treat infertility in women with anovulatory disorders. A dose of 10–40 mg per day is administered in days 3–7 of a woman's cycle. In addition, a rare condition occasionally treated with tamoxifen is retroperitoneal fibrosis.
Tamoxifen is used to prevent estrogen related gynecomastia, resulting from elevated estrogenic levels. It is taken as a preventative measure in small doses, or used at the onset of any symptoms e.g. nipple soreness/sensitivity. Other drugs are taken for the similar purposeses such as clomiphene citrate and the anti-aromatase drugs which are used in order to try to avoid the hormone related adverse effects. Tamoxifen is also sometimes used to treat or prevent gynecomastia in sex offenders undergoing temporary chemical castration.
Tamoxifen has been shown to be effective in the treatment of mania in patients with bipolar disorder by blocking protein kinase C (PKC), an enzyme that regulates neuron activity in the brain. Researchers believe PKC is over-active during the mania in bipolar patients.
Angiogenesis and cancer
Tamoxifen is one of three drugs in an anti-angiogenetic protocol developed by Dr. Judah Folkman, a researcher at Children's Hospital at Harvard Medical School in Boston. Folkman discovered in the 1970s that angiogenesis – the growth of new blood vessels – plays a significant role in the development of cancer. Since his discovery, an entirely new field of cancer research has developed. Clinical trials on angiogenesis inhibitors have been underway since 1992 using myriad different drugs. The Harvard researchers developed a specific protocol for a golden retriever named Navy who was cancer-free after receiving the prescribed cocktail of celecoxib, doxycycline, and tamoxifen – the treatment subsequently became known as the Navy Protocol. Furthermore tamoxifen treatment alone has been shown to have anti-angiogenetic effects in animal models of cancer which appear to be, at least in part, independent of tamoxifen's estrogen receptor antagonist properties.
Control of gene expression
Tamoxifen is used as a research tool to trigger tissue specific gene expression in many conditional expression constructs in genetically modified animals including a version of the Cre-Lox recombination technique.
Tamoxifen has been proposed as part of a treatment plan for Riedel's thyroiditis.
A report in September 2009 from Health and Human Services' Agency for Healthcare Research and Quality suggests that tamoxifen, raloxifene, and tibolone used to treat breast cancer significantly reduce invasive breast cancer in midlife and older women, but also increase the risk of adverse side effects.
A beneficial side effect of tamoxifen is that it prevents bone loss by acting as an estrogen receptor agonist (i.e., mimicking the effects of estrogen) in this cell type. Therefore, by inhibiting osteoclasts, it prevents osteoporosis. When tamoxifen was launched as a drug, it was thought that tamoxifen would act as an estrogen receptor antagonist in all tissue, including bone, and therefore it was feared that it would contribute to osteoporosis. It was therefore very surprising that the opposite effect was observed clinically. Hence tamoxifen's tissue selective action directly led to the formulation of the concept of selective estrogen receptor modulators (SERMs). In contrast tamoxifen appears to be associated with bone loss in premenopausal women who continue to menstruate after adjuvant chemotherapy.
Tamoxifen is a selective estrogen receptor modulator. Even though it is an antagonist in breast tissue it acts as partial agonist on the endometrium and has been linked to endometrial cancer in some women. Therefore endometrial changes, including cancer, are among tamoxifen's side effects. With time, risk of endometrial cancer may be doubled to quadrupled, which is a reason tamoxifen is typically only used for 5 years.
The American Cancer Society lists tamoxifen as a known carcinogen, stating that it increases the risk of some types of uterine cancer while lowering the risk of breast cancer recurrence. The ACS states that its use should not be avoided in cases where the risk of breast cancer recurrence without the drug is higher than the risk of developing uterine cancer with the drug.
Cardiovascular and metabolic
Tamoxifen treatment of postmenopausal women is associated with beneficial effects on serum lipid profiles. However, long-term data from clinical trials have failed to demonstrate a cardioprotective effect. For some women, tamoxifen can cause a rapid increase in triglyceride concentration in the blood. In addition there is an increased risk of thromboembolism especially during and immediately after major surgery or periods of immobility. Tamoxifen is also a cause of fatty liver, otherwise known as steatorrhoeic hepatosis or steatosis hepatis.
Central nervous system
Tamoxifen-treated breast cancer patients show evidence of reduced cognition, a major side effect of tamoxifen, and semantic memory scores. However memory impairment in patients treated with tamoxifen was less severe compared with those treated with anastrozole (an aromatase inhibitor).
A significant number of tamoxifen treated breast cancer patients experience a reduction of libido.
Premature growth plate fusion
While tamoxifen has been shown to antagonize the actions of estrogen in tissues such as the breast, its effects in other tissues such as bones has not been documented fully. There have been studies done in mice showing tamoxifen mimic the effects of estrogen on bone metabolism and skeletal growth. Thus increasing the possibility of pre-mature bone fusion. This effect would be less of a concern in adults who have stopped growing.
Tamoxifen citrate is contraindicated in patients with known hypersensitivity to the drug or any of its ingredients.
Reduction in Breast Cancer Incidence in High Risk Women and Women with DCIS Tamoxifen is contraindicated in women who require concomitant coumarin-type anticoagulant therapy or in women with a history of deep vein thrombosis or pulmonary embolus.
Before taking tamoxifen, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.If you have cancer limited to the milk ducts, or if you are taking this medication to prevent breast cancer, then this medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: a history of blood clots (e.g., deep vein thrombosis, pulmonary embolism, stroke), conditions that require treatment with a "blood thinner" (such as warfarin).If you have breast cancer and a history of blood clots/stroke, you may or may not be able to take tamoxifen. Discuss the risks and benefits with your doctor.Before using this medication, tell your doctor or pharmacist your medical history, especially of: high cholesterol/triglycerides, limited or no ability to walk (immobility), diabetes, high blood pressure, smoking, cataracts, liver disease.This medication is not recommended for use during pregnancy because it may harm an unborn baby. Consult your doctor for more details. Women of childbearing age should start tamoxifen during their periods or get a negative pregnancy test before starting the medication.It is recommended that men and women using this medication use two effective non-hormonal forms of birth control (e.g., condoms and diaphragms with spermicide) while taking this medication and for 2 months after stopping the medication. Consult your doctor.It is not known if this medication passes into breast milk. Because of the potential risk to the infant, breast-feeding is not recommended while using this drug. Consult your doctor before breast-feeding.
Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor or pharmacist first.This drug should not be used with the following medications because very serious interactions may occur: anastrozole, letrozole.If you are currently using any of these medications listed above, tell your doctor or pharmacist before starting tamoxifen.Tell your doctor or pharmacist of all prescription and nonprescription drugs you may use, especially of: ""blood thinners"" (e.g., warfarin), bupropion, estrogens, hormonal forms of birth control (e.g., birth control pills, patches, implants), phenobarbital, rifamycins (e.g., rifampin), St John's wort.Other medications can affect the removal of tamoxifen from your body, which may affect how tamoxifen works. Examples include cimetidine, SSRI antidepressants such as fluoxetine/paroxetine, among others.This medication may interfere with certain laboratory tests (including thyroid tests), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.
If overdose is suspected, contact your local poison control center . Symptoms of overdose may include: shaking, unsteady walking, fainting, irregular heartbeat.
Tamoxifen is a tablet that should be swallowed whole with a glass of water. The tablets come in different strengths: 10mg, 20mg and 40mg.
The drug is manufactured under several different brand names and these may appear on the tablets. It's also available as a sugar free syrup for people who have difficulty swallowing tablets.
Tamoxifen is usually prescribed as a single daily dose and this should be taken at the same time each day.
You may prefer to take the tablet with food as it may make you feel sick and can leave a metallic taste in your mouth. It's best to find a convenient time for you and stick to it.