Tamoxifen is an orally active selective estrogen receptor modulator that is used in the treatment of breast cancer and is currently the world's largest selling drug for that purpose. However, it has some side effects including hot flashes, menstrual irregularity, vaginal discharges, uterine bleeding, uterine endometrial cancer, hypercoagulability, steatosis hepatis, risk of trombembolism. Long-term data from clinical trials have failed to demonstrate a cardioprotective effect and beneficial effects on serum lipid profiles. Arrhythmia secondary to tamoxifen is very rare.