Fulveser 250 mg/5 mL Fulveser 250 mg/5 mL contains Fulvestrant, a hormone therapy used to treat certain types of advanced breast cancer that depend on estrogen for their growth. It works by reducing the activity of estrogen receptors in cancer cells, helping slow the growth and spread of the disease. Fulveser is commonly prescribed for postmenopausal women with hormone receptor-positive breast cancer and may be used alone or in combination with other anticancer medicines. The injection is administered by a healthcare professional as part of a planned treatment regimen.