Alternatives to Anastrozole If You Can't Fill Your Prescription

Anastrozole is one of the most widely prescribed treatments for hormone receptor-positive breast cancer in postmenopausal women — but what happens when you can't get it? Whether you're dealing with a temporary stock issue at your local pharmacy or a persistent supply problem, there are alternatives your oncologist may consider. This guide covers the most common substitutes for anastrozole, how they compare, and what questions to bring to your doctor before making any change.

Important: Never switch your breast cancer medication without talking to your oncologist first. Even drugs in the same class can have different side effect profiles and interactions. The information here is for educational purposes — your doctor makes the final call.

Why Would You Need an Anastrozole Alternative?

There are several scenarios where a patient might need to switch away from anastrozole:

Temporary or persistent local pharmacy stock issues

Intolerable side effects, especially severe joint pain

Insurance coverage changes (anastrozole removed from formulary)

Cost issues with brand-name Arimidex when generic is unavailable

Pre-existing osteoporosis (bone loss concern with anastrozole)

Letrozole (Femara) — The Most Common Alternative

Letrozole (brand name: Femara) is another non-steroidal aromatase inhibitor. Like anastrozole, it works by blocking the aromatase enzyme to reduce estrogen production. It is FDA-approved for the same indications — adjuvant treatment for early HR-positive breast cancer, first-line treatment for advanced breast cancer, and treatment after tamoxifen failure.

Clinical studies have found that letrozole and anastrozole are similarly effective overall, though some research suggests letrozole may produce slightly more complete estrogen suppression. Side effects are similar to anastrozole: hot flashes, joint pain, bone loss risk. Generic letrozole 2.5 mg can cost as little as $5–$10 per 30-day supply with discount coupons.

Key difference: Letrozole is 2.5 mg daily vs. anastrozole 1 mg daily — your oncologist will manage the dose transition.

Exemestane (Aromasin) — The Steroidal Option

Exemestane (brand name: Aromasin) is a steroidal aromatase inhibitor — it permanently binds to and deactivates aromatase, rather than reversibly blocking it like anastrozole and letrozole. It's FDA-approved for the same postmenopausal breast cancer indications.

Exemestane has a similar side effect profile to anastrozole but does have slightly different bone effects. Some studies suggest it may have a less severe impact on bone mineral density in certain patients. The key practical difference: exemestane must be taken with food, unlike anastrozole which can be taken with or without food. Generic exemestane costs approximately $10–$20 per 30-day supply with coupons.

Tamoxifen — When Aromatase Inhibitors Aren't an Option

Tamoxifen is a selective estrogen receptor modulator (SERM) — it works differently from aromatase inhibitors. Instead of reducing estrogen production, tamoxifen blocks estrogen from binding to estrogen receptors on breast cancer cells. It is FDA-approved for breast cancer treatment in both pre- and postmenopausal women.

For postmenopausal women, aromatase inhibitors like anastrozole have generally shown superior efficacy to tamoxifen in clinical trials. However, tamoxifen is sometimes used when aromatase inhibitors cannot be tolerated (due to severe bone loss or other reasons) or when they are unavailable. Tamoxifen cannot be taken at the same time as anastrozole — the combination reduces anastrozole's effectiveness.

Fulvestrant (Faslodex) — For Advanced Disease

Fulvestrant (brand name: Faslodex) is an estrogen receptor degrader (SERD) used for advanced or metastatic HR-positive breast cancer. It is administered as a monthly injection and is not a direct substitute for daily oral anastrozole in early-stage settings. It's typically used after aromatase inhibitor failure or in combination with CDK4/6 inhibitors.

How to Talk to Your Oncologist About Switching

If you need to switch due to a supply issue, come prepared to your appointment:

Tell your oncologist specifically which pharmacies you've tried and how long the stock issue has persisted

Ask whether letrozole or exemestane would be an appropriate short-term substitute

Ask whether there is a bone density consideration for your specific case that might favor one drug over another

Ask if they can provide samples to bridge you while supply is found

Before You Switch: Try These First

If the issue is simply that your regular pharmacy is temporarily out of stock, it may be worth searching more broadly before switching medications. medfinder can call pharmacies in your area to find one that has anastrozole in stock — often the medication is available nearby even when your go-to pharmacy is out. Switching medications carries its own risks and requires oncologist supervision, so exhausting your search options first makes sense.

Learn More

See our guide on how to find anastrozole in stock near you and read the latest anastrozole shortage update for 2026.