Uses

Fulvestrant is an estrogen receptor antagonist indicated for hormone receptor-positive, HER2-negative advanced breast cancer in postmenopausal women, either as initial endocrine-based therapy or following disease progression on prior endocrine therapy. It may be used in combination with CDK4/6 inhibitors such as ribociclib.

Do not use if

Contraindicated in patients with known hypersensitivity to fulvestrant or any component of the formulation, including those who have experienced urticaria or angioedema. Contraindicated during pregnancy.

Side effects

Common adverse reactions include injection site pain, nausea, fatigue, musculoskeletal pain, hot flashes, and elevated liver enzymes. Risk of bleeding at injection site is increased in patients on anticoagulants or with thrombocytopenia.

Warnings

Use with caution in patients with bleeding diatheses, thrombocytopenia, or anticoagulant therapy due to risk of injection-site bleeding. Reduce dose in moderate hepatic impairment; avoid in severe hepatic impairment. May cause embryo-fetal toxicity; effective contraception required in women of reproductive potential.

How it works

Fulvestrant competitively binds to estrogen receptors with affinity comparable to estradiol, leading to downregulation and degradation of the ER protein in breast cancer cells. Unlike selective estrogen receptor modulators, fulvestrant has no agonist activity and acts as a pure estrogen receptor antagonist, blocking estrogen-driven tumor growth.

Storage

Refrigerate at 2°C to 8°C (36°F to 46°F). Store in the original carton to protect from light until time of use.