Anastrozole: Practical Guide for Patients and Caregivers

Anastrozole (brand name Arimidex) is an aromatase inhibitor used mainly in postmenopausal women with estrogen receptor–positive breast cancer. It lowers the body's estrogen production to slow or stop the growth of hormone-sensitive tumors. If your doctor suggested anastrozole, here’s what you need to know in plain language.

How anastrozole works and who uses it

Anastrozole blocks an enzyme called aromatase that turns androgens into estrogen. Less estrogen usually means less fuel for certain breast cancers. Doctors commonly prescribe it after surgery, as adjuvant therapy, or for metastatic disease in postmenopausal women. It’s not for use during pregnancy or in premenopausal women unless ovarian function is suppressed by other treatments.

Typical medical dosing is 1 mg once daily by mouth. Take it at about the same time each day. Swallow the tablet whole—no crushing. If you miss a dose, take it as soon as you remember unless it’s almost time for the next dose; don’t double up.

What to expect: common side effects and monitoring

Most people notice a few predictable side effects. Hot flashes, joint or muscle pain, fatigue, nausea, and mood changes are common. Long-term use can reduce bone density and may raise cholesterol. Your care team will usually check bone health (DEXA scans) and lipid levels during treatment. Report new or worsening bone pain, sudden swelling, vision changes, or signs of a blood clot right away.

Managing side effects: simple steps help. Regular weight-bearing exercise, calcium and vitamin D, and bone-building drugs when recommended can protect your bones. For joint pain, gentle stretching, over-the-counter pain relievers, and talking to your doctor about dose timing often help. If fatigue hits, short naps, light activity, and pacing tasks make a big difference.

Drug interactions are limited but important. Avoid estrogen-containing products or hormone replacement therapy while on anastrozole. Tell your doctor about all meds and supplements, especially strong CYP enzyme modifiers—though anastrozole has fewer interactions than some drugs, it's best to check.

Pregnancy and fertility: do not use if pregnant or trying to conceive. Use reliable contraception if you or a partner could become pregnant. Discuss fertility concerns with your oncologist before starting treatment.

Buying and safety: always get anastrozole from a licensed pharmacy with a valid prescription. If ordering online, confirm the pharmacy is reputable and requires a prescription. Counterfeit meds are a real risk and can be dangerous.

If side effects become unbearable or you worry about risks, talk with your oncologist. They can adjust treatment, switch drugs, or add supportive care. Short, clear conversations with your care team make a big difference in how tolerable treatment feels.