Fulvestrant Injection for HR+ Metastatic Breast Cancer (Faslodex®)

What Fulvestrant Is and How It Works

Fulvestrant is an estrogen receptor antagonist and degrader used for hormone receptor–positive, HER2‑negative advanced or metastatic breast cancer. It is given as an intramuscular fulvestrant injection by a healthcare professional. The usual regimen is a loading schedule followed by monthly maintenance dosing.

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Fulvestrant belongs to the class of selective estrogen receptor downregulators (SERDs). It binds to the estrogen receptor (ER), blocks estrogen signaling, and speeds ER degradation. This slows tumor growth in ER‑driven cancers. It is used alone after progression on prior endocrine therapy, or with a CDK4/6 inhibitor as first‑ or later‑line therapy.

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Dosage and Usage

Fulvestrant is a deep intramuscular injection into the buttock (gluteal muscle). A healthcare professional administers the dose as two injections, one in each buttock.

• Standard adult dosing: 500 mg on Days 1, 15, and 29, then 500 mg every 28 days.
• Moderate hepatic impairment: many guidelines recommend 250 mg on the same schedule; specialist direction applies.
• Combination therapy: dosing is the same when used with palbociclib, ribociclib, or abemaciclib.
• Missed dose: contact the clinic to reschedule as soon as possible.
• Preparation: the syringe may be allowed to reach room temperature before injection per product instructions.

Storage and travel

• Store in a refrigerator at 2–8°C (36–46°F). Keep in the original carton to protect from light.
• Do not freeze. Do not shake. Keep out of children’s reach.
• If you travel, use an insulated container with cold packs. Avoid direct contact with ice.
• Do not use if the solution is cloudy, discoloured, or contains particles.

Benefits and Savings

Fulvestrant lowers estrogen‑driven signaling by degrading ER. Clinical studies show improved progression‑free survival, especially when combined with a CDK4/6 inhibitor. The monthly maintenance schedule reduces daily pill burden. Many patients tolerate therapy without hair loss.

You can access Canadian pricing at YouDrugstore, which often means 60–80% savings versus typical US pharmacy prices. We offer brand Faslodex® and quality generics, including options from major manufacturers such as Sandoz when available. Our team can help with product selection, and our chat is available during posted hours.

Side Effects and Safety

• Common: injection site pain, bruising, or swelling; nausea; fatigue; headache; hot flashes; joint or muscle pain; mild diarrhea or constipation.
• Liver: increased AST/ALT; rare hepatitis. Liver function monitoring may be used.
• Blood and injection risks: bleeding or hematoma risk increases with thrombocytopenia or anticoagulants.
• Neuromuscular: sciatica or neuropathic pain has rarely occurred due to deep gluteal injection.
• Allergy: hypersensitivity or anaphylaxis is rare.
• Reproductive: can cause fetal harm. Use effective contraception during treatment and for a period after the last dose as advised by a clinician. Do not use during pregnancy or breastfeeding.

People with moderate hepatic impairment often receive a reduced dose. Severe hepatic impairment has not been studied. Always inform the clinic about bleeding disorders, anticoagulant use, or allergies to ingredients (e.g., benzyl alcohol).

Onset Time

Fulvestrant has a long half‑life. The loading doses reach therapeutic levels faster. Symptom improvement may appear within several weeks, and radiologic response often appears over 1–3 months. Combination regimens with CDK4/6 inhibitors may show earlier disease control compared with fulvestrant alone.

Compare With Alternatives

Aromatase inhibitors (AIs) reduce estrogen production. Options include Anastrozole and Exemestane. AIs are oral and may be used first‑line in postmenopausal patients or men with HR+ disease. After progression on an AI, fulvestrant is a common next step, often paired with a CDK4/6 inhibitor.

Selective estrogen receptor modulators (SERMs), such as tamoxifen, block ER but do not degrade it. Fulvestrant may be preferred after SERM failure due to its receptor‑degrading action.

CDK4/6 inhibitor combinations have become a key standard. Fulvestrant plus palbociclib (Ibrance®), ribociclib (Kisqali®), or abemaciclib (Verzenio®) improves progression‑free survival versus fulvestrant alone in several trials.

HER2‑positive disease is managed differently. In those cases, anti‑HER2 therapy is central. Oral tucatinib, for example, is used with trastuzumab and capecitabine; you can review Tukysa® if HER2‑positive therapy is relevant to your plan.

Combination Therapy

Fulvestrant is often combined with a CDK4/6 inhibitor to delay progression. Common pairs include fulvestrant plus palbociclib (Ibrance®), ribociclib (Kisqali®), or abemaciclib (Verzenio®). These agents inhibit cyclin‑dependent kinases 4 and 6, which control cell cycle progression. The combination targets both hormonal signaling and cell cycle checkpoints.

Other targeted partners can be used in selected settings. PIK3CA‑mutated tumors may receive alpelisib with a different endocrine backbone. Everolimus may be used with an AI after progression. Your oncology team decides on sequencing and combinations based on prior therapy, menopausal status, biomarkers, and tolerance. For background on CDK4/6 therapy, see our article How Ibrance Palbociclib Helps In Breast Cancer Management.

Patient Suitability and Cost-Saving Tips

Fulvestrant is indicated for postmenopausal women and men with HR+ HER2‑negative advanced or metastatic breast cancer. It may be used in premenopausal women with ovarian suppression. It is given by a trained professional to reduce nerve injury risk and ensure correct deep IM technique. Moderate hepatic impairment often warrants dose reduction. Severe hepatic impairment, pregnancy, and active bleeding disorders are reasons to review alternatives.

You can lower monthly costs by choosing multi‑month quantities when possible. Reorder reminders help you stay on schedule. Bulk promotions may reduce the per‑month price when permitted. Our customer-service chat can guide product options and availability during office hours.

Learn more about the condition in our Breast Cancer and Cancer sections. For a primer on this therapy, read Fulvestrant Injection Hormone Therapy For Breast Cancer.

Authoritative Sources

Faslodex (fulvestrant) Prescribing Information – FDA

Health Canada Drug Product Database – Faslodex (fulvestrant)

AstraZeneca Faslodex® Product Page

YouDrugstore makes it simple to fill your oncology prescription at Canadian prices. Our licensed pharmacists verify your prescription, and our team supports your order from checkout to delivery. We offer prompt, express, cold-chain shipping to the US for temperature‑sensitive items like fulvestrant.

Disclaimer: This information is not a substitute for professional medical advice. Always follow your oncologist’s instructions and the product monograph. Report side effects to your care team. Product availability, manufacturers, and packaging may vary by lot and jurisdiction.