Nolvadex: Advanced Estrogen Receptor Modulation for Breast Cancer
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Synonyms
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Nolvadex (tamoxifen citrate) represents a cornerstone in the endocrine therapy of hormone receptor-positive breast cancer. As a selective estrogen receptor modulator (SERM), it exerts its therapeutic effects by competitively inhibiting estradiol binding at estrogen receptors in breast tissue, thereby impeding the proliferation of malignant cells. Its well-established efficacy profile and extensive clinical history make it a first-line option for both early and advanced-stage disease in pre- and postmenopausal women. This comprehensive guide details the pharmacological characteristics, appropriate usage, and essential safety information for healthcare professionals managing patients on this critical therapy.
Features
- Active Ingredient: Tamoxifen citrate
- Therapeutic Class: Selective Estrogen Receptor Modulator (SERM)
- Available Formulations: 10 mg and 20 mg oral tablets
- Bioavailability: High oral bioavailability with peak plasma concentrations reached within 4-7 hours post-administration
- Metabolism: Hepatic, primarily via CYP2D6 and CYP3A4 isoenzymes, producing active metabolites like endoxifen
- Elimination Half-life: Approximately 5-7 days for tamoxifen and 14 days for primary metabolites, facilitating once or twice-daily dosing
- Special Packaging: Blister packs ensuring stability and protection from moisture
Benefits
- Significant Reduction in Recurrence: Demonstrated up to 50% reduction in the risk of breast cancer recurrence in hormone receptor-positive disease
- Mortality Reduction: Associated with a 31% reduction in mortality at 15 years in early breast cancer patients when administered for 5 years
- Contralateral Breast Cancer Prevention: Reduces incidence of new primary breast cancer in the opposite breast by approximately 50%
- Bone Density Preservation: Exhibits estrogen-agonist effects on bone metabolism, helping maintain bone mineral density in premenopausal women
- Favorable Lipid Profile: Generally improves serum lipid parameters, potentially offering cardiovascular benefits
- Flexible Treatment Duration: Evidence supports efficacy across standard 5-year regimens and extended 10-year therapy in selected cases
Common use
Nolvadex is primarily indicated for the treatment of hormone receptor-positive breast cancer across multiple clinical scenarios. It serves as adjuvant therapy following primary treatment (surgery, radiation, chemotherapy) in both premenopausal and postmenopausal women with early-stage invasive breast cancer. For advanced or metastatic disease, it provides effective systemic treatment that can delay disease progression. Additionally, it’s approved for risk reduction in high-risk women (those with LCIS, atypical hyperplasia, or ≥1.67% 5-year Gail model risk) and for ductal carcinoma in situ (DCIS) following breast-conserving surgery and radiation to reduce the risk of invasive breast cancer. Off-label uses include management of gynecomastia and ovulation induction in certain fertility protocols, though these applications require careful risk-benefit assessment.
Dosage and direction
The standard adult dosage for breast cancer treatment is 20 mg once daily, though some protocols initiate therapy at 40 mg daily divided into two doses (20 mg twice daily) for the first month before reducing to maintenance dosing. For DCIS and risk reduction, the recommended dose is 20 mg daily. Administration should occur at approximately the same time each day, with or without food, though consistency in relation to meals is advised to maintain steady pharmacokinetics. Tablets should be swallowed whole with water and not crushed or chewed. Treatment duration typically spans 5-10 years based on individualized risk assessment and tolerance. For premenopausal women, concomitant ovarian suppression may be considered in higher-risk scenarios. Dosage adjustments may be necessary in patients with hepatic impairment or those taking strong CYP2D6 inhibitors.
Precautions
Regular monitoring is essential throughout Nolvadex therapy. Baseline and periodic gynecological examinations are mandatory due to increased risk of endometrial changes, including cancer. Patients should report any abnormal vaginal bleeding, pelvic pain, or pressure promptly. Ophthalmological evaluations are recommended for patients reporting visual changes, as retinal changes and cataracts have been associated with long-term use. Liver function tests should be performed at baseline and periodically during treatment, particularly during the first few months. Blood lipid monitoring is advised, especially in patients with preexisting dyslipidemia. Bone mineral density assessment may be considered in premenopausal women, despite the bone-protective effects, to establish baseline status. Patients should be advised about the potential for hot flashes and other vasomotor symptoms, which are common but generally manageable.
Contraindications
Nolvadex is contraindicated in patients with known hypersensitivity to tamoxifen citrate or any component of the formulation. It must not be used concomitantly with anastrozole or other aromatase inhibitors in premenopausal women, as this combination is ineffective. Additional contraindications include treatment during pregnancy (Pregnancy Category D) due to potential fetal harm, and in women who are breastfeeding. Patients with a history of deep vein thrombosis or pulmonary embolism should generally avoid tamoxifen unless no alternative exists and benefits clearly outweigh risks. Concurrent warfarin therapy requires extreme caution and frequent monitoring. The presence of CYP2D6 poor metabolizer status may warrant consideration of alternative therapies due to reduced efficacy.
Possible side effect
The most frequently reported adverse reactions include hot flashes (occurring in approximately 80% of patients), vaginal discharge or dryness, and menstrual irregularities. Gastrointestinal disturbances such as nausea and vomiting affect 20-25% of patients, though these often diminish with continued therapy. More serious but less common effects include venous thromboembolic events (deep vein thrombosis, pulmonary embolism) with an approximate 1-2% incidence, and endometrial cancer (risk increased 2- to 3-fold compared to placebo). Ocular complications such as cataracts (relative risk ~1.5) and retinopathy may occur with prolonged use. Hepatic effects range from mild transaminase elevations to rare cases of fatty liver, cholestasis, and hepatitis. Musculoskeletal pain and mood disturbances, including depression, are reported in 10-15% of patients. Rare cases of hypertriglyceridemia, especially in patients with preexisting lipid disorders, have been documented.
Drug interaction
Nolvadex exhibits several clinically significant interactions. Strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine, quinidine) reduce the conversion to active metabolites, potentially diminishing efficacy—alternative antidepressants like venlafaxine or citalopram are preferred. Warfarin coadministration increases anticoagulant effect and bleeding risk, requiring frequent INR monitoring and possible warfarin dose reduction. CYP3A4 inducers (rifampin, carbamazepine, St. John’s wort) may decrease tamoxifen concentrations, while inhibitors (ketoconazole, erythromycin) may increase levels. Tamoxifen itself may enhance the thrombogenic potential of other drugs that promote coagulation. Concomitant use with other estrogen-containing therapies negates its therapeutic effect and is contraindicated.
Missed dose
If a dose is missed, patients should take it as soon as remembered unless it is nearly time for the next scheduled dose. In that case, the missed dose should be skipped, and the regular dosing schedule resumed. Doubling the dose to make up for a missed dose is not recommended. Consistency in dosing is important for maintaining stable drug levels, but occasional missed doses are unlikely to significantly impact overall efficacy given the long half-life of tamoxifen and its metabolites. Patients should be instructed to maintain a dosing diary or use pill organizers to enhance adherence, particularly during long-term therapy.
Overdose
Acute overdose with Nolvadex may produce symptoms including tremor, hyperreflexia, unsteady gait, dizziness, and nausea. Severe overdose might result in QT prolongation, convulsions, or coma. There is no specific antidote for tamoxifen overdose. Management consists of supportive care with continuous ECG monitoring for at least 24 hours to detect QT prolongation. Gastric lavage may be considered if presentation is early after ingestion. Activated charcoal can be administered if the patient presents within 1-2 hours of ingestion. Seizures should be managed with benzodiazepines; antiarrhythmic agents may be required for significant cardiac effects. Given the drug’s extensive tissue distribution, dialysis is not effective.
Storage
Nolvadex tablets should be stored at controlled room temperature (20-25°C or 68-77°F) in their original packaging to protect from light and moisture. Excursions are permitted between 15-30°C (59-86°F). The tablets should be kept in a secure location out of reach of children and pets. Unused medication should be properly disposed of according to local regulations, preferably through drug take-back programs. Patients should be advised not to store medication in bathrooms or other areas with high humidity, which could degrade the product. Do not use tablets that show signs of discoloration or physical deterioration.
Disclaimer
This information is intended for healthcare professionals and represents a summary of Nolvadex’s characteristics based on current prescribing information and clinical literature. It does not encompass all possible uses, directions, precautions, or adverse effects. Treatment decisions must be made by qualified healthcare providers considering individual patient circumstances. Dosage and administration should follow the approved product labeling and current clinical guidelines. Patients should be fully informed of benefits and risks, and monitored appropriately throughout therapy. The prescribing physician should be consulted for specific medical advice.
Reviews
Clinical studies consistently demonstrate Nolvadex’s efficacy in reducing breast cancer recurrence and mortality. The NSABP B-14 trial established the 5-year adjuvant regimen, showing 49% reduction in recurrence risk. Subsequent meta-analyses by the Early Breast Cancer Trialists’ Collaborative Group confirmed persistent benefit with 10-year follow-up, showing maintained reduction in recurrence and mortality. The ATLAS trial further supported extended therapy for 10 years, demonstrating additional risk reduction compared to 5-year treatment. Patient-reported outcomes indicate generally good tolerance, though vasomotor symptoms and sexual side effects impact quality of life for some individuals. Overall, the risk-benefit profile remains favorable for appropriate candidates, with decades of clinical experience supporting its position in breast cancer therapeutics.