Fasvivo Injection contains Fulvestrant 50mg/ml, a selective estrogen receptor degrader used primarily in the treatment of hormone receptor-positive metastatic breast cancer in postmenopausal women. Fulvestrant works by binding to estrogen receptors, leading to their degradation and downregulation, thereby inhibiting estrogen-driven tumor growth. Administered via intramuscular injection, Fasvivo is typically given once a month, allowing for sustained suppression of estrogen receptor activity. This medication is particularly beneficial for patients who have progressed on prior endocrine therapy such as tamoxifen or aromatase inhibitors. Common side effects may include injection site reactions, nausea, fatigue, hot flashes, and mild gastrointestinal disturbances. Fasvivo should be used under strict medical supervision, with monitoring for liver function and potential drug interactions. It is contraindicated in patients with known hypersensitivity to Fulvestrant or any of its excipients. Pregnant or breastfeeding women should avoid this medication due to potential risks to the fetus or infant. Fasvivo Injection offers an effective therapeutic option for managing advanced breast cancer by targeting estrogen receptor pathways, improving patient outcomes and quality of life when used as part of a comprehensive oncologic treatment plan.