Fasvivo contains Fulvestrant, a selective estrogen receptor degrader (SERD) used to treat hormone receptor-positive breast cancer in postmenopausal women. It works by binding to estrogen receptors, resulting in their degradation, which prevents estrogen from stimulating tumor growth.

Uses

Breast Cancer (HR-positive):

• Treatment of estrogen receptor-positive, HER2-negative breast cancer in postmenopausal women who have progressed on anti-estrogen therapy like tamoxifen.

Combination with Other Drugs:

• Used in combination with other therapies for advanced or metastatic breast cancer.

Fulvestrant binds to estrogen receptors on cancer cells, leading to their degradation. This prevents the estrogen receptor from activating genes responsible for cancer cell growth and proliferation.

Onset of Action

• Fulvestrant begins to show therapeutic effects within 2-3 weeks after the first dose.

Duration of Action

• The duration of action can last for several weeks, with periodic doses typically administered every 4 weeks.

Dosage

• Initial Dose: 500 mg (administered as two 250 mg injections) on Day 1 and Day 15.
• Maintenance Dose: 500 mg administered once a month (every 4 weeks) thereafter.

Common Side Effects

• Injection site reactions (pain, redness, swelling)
• Hot flashes
• Nausea
• Fatigue
• Headache
• Musculoskeletal pain
• Liver enzyme abnormalities (elevated liver function tests)

Precautions

• Liver Impairment: Use cautiously in patients with liver disease.
• Monitor for signs of thromboembolic events (e.g., deep vein thrombosis, pulmonary embolism).
• Not recommended during pregnancy or breastfeeding.

Drug Interactions

• CYP3A4 inhibitors (e.g., ketoconazole): Can increase Fulvestrant levels.
• CYP3A4 inducers (e.g., rifampin): May decrease Fulvestrant levels.
• Warfarin: Regular monitoring of INR is recommended when used with Fulvestrant.

Storage

• Store at room temperature (20-25°C). Do not freeze.