Raloxifene

Class & Mechanism:

• Selective Estrogen Receptor Modulator (SERM)
• Antagonist on estrogen receptors in breast and uterine tissue, agonist on estrogen receptors in bone and lipid metabolism.
• Unlike tamoxifen, no agonist activity in the endometrium, so no increased endometrial cancer risk.

Oncology & Preventive Indications:

• Primary prevention of invasive breast cancer in postmenopausal women at high risk (e.g., LCIS, strong family history, Gail model ≥1.66%).
• Not used for treatment of established breast cancer.
• Also indicated for prevention and treatment of postmenopausal osteoporosis (dual benefit in some patients).

Dose & Administration:

• 60 mg orally once daily, with or without food.

Pharmacist Considerations:

Advantages in Oncology Prevention Setting:

• Reduces risk of ER+ invasive breast cancer by ~50% in high-risk postmenopausal women.
• Lower incidence of endometrial cancer vs tamoxifen.

Adverse Effects:

• Common: hot flashes, leg cramps, peripheral edema.
• Serious: increased risk of venous thromboembolism (DVT, PE) — similar magnitude to tamoxifen.
• No increased risk of endometrial carcinoma.

Monitoring:

• Monitor for VTE symptoms (leg swelling, pain, sudden shortness of breath).
• Bone mineral density (if also used for osteoporosis).

Counseling Points:

• Advise patients to remain active and avoid prolonged immobility to reduce VTE risk.
• Report any unexplained vaginal bleeding (rare, but warrants evaluation).
• Not recommended for premenopausal women or for treatment of existing breast cancer.

Drug Interactions:

• Minimal CYP metabolism — fewer drug-drug interactions compared to tamoxifen.
• Use caution with other drugs that increase clotting risk.