Breast cancer is about 22.9% of the total cancers worldwide, and in 2008 it accounts 458,503 deaths around the world. Breast cancer occurs when there is a formation of cancerous tumors in the breast tissue. It is good to hear that if detected early, breast cancer has found to have a survival rate of 90% with proper medication. One of the prescribed medicines for breast cancer is the tamoxifen citrate.
Antiestrogen tamoxifen citrate acts by competing with the estradiol for receptor sites. Tamoxifen citrate is the drug of choice for breast cancer involving estrogen receptor positive tumors in postmenopausal women. Tamoxifen citrate is available in oral form and it is absorbed well in the body and undergoes extensive hepatic metabolism before fecal excretion. It has a half-life of approximately 1 week.
Even though tamoxifen citrate is being absorbed by our body well, its distribution has not been studied thoroughly. The drug is metabolized in the liver to various metabolites that display antiestrogenic and antitumor effects. Tamoxifen citrate and its metabolites are excreted slowly in feces, mainly as conjugate. Less than 30% of a dose is excreted as other metabolites or the parent compound. Minimal amounts are excreted in the urine.
The peak oral serum concentration level of tamoxifen citrate occurs in 3 to 6 hours after oral dose. The half-life of the drug is approximately 7 days. The steady state blood level is achieved in 4 weeks. Clinical responses usually appear in 1 to 2 months.
Estrogen receptors, found in the cancer cells of 50% of premenopausal and 75% of postmenopausal women with breast cancer, respond to estrogenic influence to induce tumor growth. The antiestrogen tamoxifen citrate binds to the estrogen receptors and inhibits the estrogen-mediated tumor growth. The inhibition may result because tamoxifen citrate binds to receptors at the nuclear level or because the binding reduces the number of free receptors in the cytoplasm. Ultimately, deoxyribonucleic acid (DNA) synthesis and cell growth are inhibited.
The Tamoxifen citrate or Nolvadex is indicated for the palliative treatment of metastatic breast cancer that is estrogen receptor-positive. Tumors in postmenopausal women are more responsive to Tamoxifen citrate than those premenopausal women. Tamoxifen citrate may also be used as an adjunct to surgery in postmenopausal women with axillary lymph nodes that contain cancer cells and estrogen receptor-positive tumors. The drug may be used alone with cytotoxic agents. The usual dosage of Tamoxifen citrate for adults ranges from 10 to 20 mg P.O. b.i.d. or 10 to 20 mg of tablet twice a day. There are no drug interactions that have been identified for tamoxifen citrate and also tamoxifen citrate is a non-toxic drug.
However, just like any other drugs, Tamoxifen citrates have some side effects. The most common adverse reactions are hot flashes, nausea, and vomiting. Transient mild leukopia or thrombocytopenia occurs in about 4% of patients. In patients with bone metastases, hypercalcemia may occur. About 1% of patients treated with Tamoxifen citrate may experience tumor flare, which may increase the number and size of lesions or increase bone pain. Patients receiving high doses of Tamoxifen citrate have experienced ocular lesions, retinopathy, and superficial corneal opacity, which reduce visual acuity.