Nolvadex Review Article
Nolvadex (tamoxifen) is used in the treatment of some kind of breast cancer. Nolvadex is recommended for women who are at high risk for breast cancer and for women with DCIS, but after surgery and radiation. It blocks female hormone called estrogen there by preventing the growth of tumours that are activated by estrogen. Hormones that cause breast cancer growth may also be blocked by ovarian function suppression using drugs, surgery or radiation to the ovaries. It is not yet known if giving ovarian function suppression together with tamoxifen citrate or exemestane is more effective than giving tamoxifen citrate alone in treating breast cancer.
Background of disease which the drug treat
After Lung cancer, breast cancer is classified as the most common type of cancer worldwide. According to the World Health Organization, over 1 million new cases are being diagnosed annually. In 2000, almost 400,000 women died from it, representing about 1.6% of all female deaths, and in 2008, about 480,000 women. It is the fifth leading cause of cancer death. Continue reading...
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The etiology of breast cancer is unknown, but risk factors have been identified to be associated with it, which includes family history, genetics, gynecological history, oral contraceptive pills, radiation and to a lesser content, diet. Because of the hazard it poses, several organizations and health activists have advocated the fight against breast cancer. According to the World Health Organization, breast cancer is a type of cancer that is preventable and treatable. With the appropriate awareness, education, and therapy, breast cancer mortalities can be prevented.
Mechanism of action: Selective Estrogen Receptor Modulator
Nolvadex is the most widely studied estrogen treatment for breast cancer. It was first synthesized in 1966, and after three decades, it was proven that the success in the fight against breast cancer have been due to its widespread use. In fact, according to Hermon and Beral (1996), the reduction in breast cancer mortality is due Nolvadex.
ER+ breast cancer is a type of cancer wherein the tumor cells are dependent on estrogen for proliferation - requiring it for their growth. Therefore, selectively antagonizing estrogen on these tumor cells will lead to their diminished activity, leading to decreased proliferation and growth.
Nolvadex is the first compound of the SERMs drug class. Being a SERM, it acts selectively as an antagonist on estrogen receptors in the breast tissue, but acts as an agonist in other tissues like the uterine endometrium, the coagulation system, bone homeostatis and liver function. The decreased estrogen levels in the breast leads to breast tumor cell inhibition, an effective targeted approach for treating this type of cancer. The agonist effects of Nolvadex on other systems are responsible for its side effects, as well as other possible indications: endometrial hypertrophy, vaginal bleeding, uterine and endometrial cancers, thromboembolism, bone density modulation and altered blood lipid profile (Ellis and Swain, 2001).
Several studies have proven the effectiveness of Nolvadex for the treatment of breast cancer. The Nolvadex Adjuvant Tiral Organization (NATO) study has concluded that there is an overall disease-free survival advantage for patients using Nolvadex. Two studies made by the Swedish Breast Cancer Cooperative Group in 1996 and Early Breast Cancer Trialists’ Collaborative Group in 1998 have found that a five adjuvant therapy of Nolvadex is the superior duration of therapy as compared to one or two year use.
Nolvadex has also been proven to be effective as a prophylactic agent. In the study made by the National Cancer Institute in 1998 and 2005, they have found that Nolvadex can prevent the development of breast cancer. This finding was similar to the results obtained by Strasser-Weippl and Goss (2004). The National Cancer Institute recommends a five year prophylactic therapy with Nolvadex; beyond five years, no further benefit has been observed. A 69% reduction in the occurence of ER+ breast cancer was observed in the said study.
In a study made by Williamson and Ellis (2005), they have found that Nolvadex is an effective agent for inducing ovulation. In their study, 81% patients with anovulatory infertility had a successful ovulation. In the meta-analysis made by Steiner, Terplan and Paulson (2005), they found that the efficacy of Nolvadex to for inducing ovulation is similar to clomiphene, the first line ovulating agent (Wolf, 2000).
Other Indications: Osteoporosis, Brain Tumors, Gynecomastia
It is known that when a woman reaches the menopausal age, hormonal levels are decreased significantly, specifically estrogen. This decrease in estrogen levels is the reason for the several observed physiological changes in the body, the most significant of which is the effects on the skeletal system. Estrogen promotes bone formation and decreased bone resorption. Due to the decreased estrogen level, menopausal women experiences bone deterioration, and are at a significant risk for having osteoporosis (Prince et al., 1991; Belchetz, 1994).
Nolvadex, being a SERM, have agonist effects at the bone tissues. It is used as a drug therapy for osteoporosis. Studies made by Love and colleagues (1992), Ramaswamy and Shapiro (2003) have found that Nolvadex in osteoporosis is therapeutically beneficial. Love and colleagues found that a 0.61% increase in lumbar bone density is possible, while Ramaswamy and Shapiro found that Nolvadex is able to preserve the mineral density of bones in post menopausal women.
In a study made by Fine and colleagues (2006), they explored the possibility of using Nolvadex as a treatment for brain tumors. Nolvadex was found to inhibit P-glycoprotein, an important agent in the development of brain tumors. Fine and colleagues determined the possibility of using Nolvadex as an adjuvant to paclitaxel for the treatment of metastatic brain tumors – they found that Nolvadex may be used for brain tumors. Further research is needed to determine if it can be used clinically.
Gynecomastia is a hormonal disorder wherein men develops breast tissue enlargement. It is commonly caused as a consequence of some drugs, but in some instances it is estrogen mediated. Nolvadex may be used for estrogen mediated gynecomastia, antagonizing estrogen in breast tissues.
Possible Side effects
Hot flushes is the most common side effect of Nolvadex (Sweetman, 2009). Hot flushes, nausea and vomiting is experienced by 25% of patients. Other side effects include fluid retention, gastrointestinal intolerance, rashes, dry skin, vaginal bleeding/discharge, dizziness, headache, fatigue and muscle cramps (Sweetman, 2009).
There is a potentially life threatening drug interaction between coumarin anticoagulants like warfarin and Nolvadex (Ritchie, 1989; Tenni, et al., 1989), where the anticoagulant effects are increased. Prothrombin time prolongation, as well as hematuria and hematoma have all been reported with concomitant use of the two drugs.
In a study made by Kivisto, et al. (1998), it was found that the plasma levels of Nolvadex are reduced when used together with rifampicin, an antibacterial used for tuberculosis. It was hypothesized that this was due to the enzyme inducing effects of the said antibacterial.
The effects of bromocriptine, a dopaminergic agent used in Parkinson’s disease, are increased when concomitantly used with Nolvadex.
Precautions and Safety
It is recommended that the patients who are at risk for thromboembolism to avoid using Nolvadex, due to the reports of thromboembolitic and pulmonary embolitic events. In a cohort study by McDonald and colleagues (1995), they have proven that Nolvadex predisposes patients to a higher risk for thromboembolism. Though anticoagulants may be used, drug interaction is also of concern.
As mentioned, Nolvadex is a SERM with agonistic effects in the uterus. Nolvadex stimulates the endometrieum, which may predispose patients to the development of uterine (Wickerham, 2002) and endometrial cancer (Fisher, et.al., 1998, 2005), as well as endometrial polyps (Buijs, et al., 2004). The increased risk of developing cancer was found to be 2.53x more than those not using Nolvadex (Fisher, et al., 1998). According to the American College of Obstetrics and Gynecologists, it is recommended that should the first signs of hyperplasia develops, Nolvadex is stopped and hysterectomy is considered.
As a treatment for breast cancer, the recommended dose of Nolvadex is 20mg daily, given once or in two divided doses. Studies suggest that adjuvant therapy be continued up to five years (Sweetman, 2009).
As a prophylactic agent for high risk patients, the approved dose of Nolvadex is 20mg daily given for five years (Sweetman, 2009).
Finally, for induction of ovulation, 20mg Nolvadex on day 2 to day 5 of the menstrual cycle is recommended. For patients with irregular menstrual cycle, Nolvadex is given on any day. If menstruation occurs, dosing is then given every day 2 of the cycle. If there is no response, a subsequent dose is given 45 days after the initial treatment (Sweetman, 2009).
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Nolvadex Review Article