Anastrozole Shortage: What Providers and Prescribers Need to Know in 2026

Anastrozole remains one of the most frequently prescribed adjuvant therapies for hormone receptor-positive breast cancer in postmenopausal women, with millions of patients currently on long-term maintenance therapy. While the drug does not currently appear on the FDA's active shortage list, prescribers are increasingly fielding calls from patients who cannot locate anastrozole at their local pharmacy. This guide is designed to help oncologists, OB-GYNs, and primary care providers navigate supply disruptions efficiently and protect continuity of care.

Current Supply Landscape for Anastrozole

As of 2026, no active FDA national shortage of anastrozole has been declared. The drug is manufactured by multiple FDA-approved generic pharmaceutical companies, including Teva, Cipla, Accord Healthcare, Eugia Pharma, and Zydus Pharmaceuticals. This manufacturing diversity provides meaningful supply resilience compared to single-source agents.

However, localized supply disruptions remain a clinical reality. These arise from wholesaler allocation interruptions, pharmacy-level inventory management, and occasional upstream manufacturing delays at specific generic manufacturers. Internationally, Australia experienced a documented shortage of the ARIANNA brand of anastrozole tablets in mid-2025, resolved by November 2025. Global API sourcing vulnerabilities — predominantly from Indian and Chinese manufacturing facilities — can create ripple effects in U.S. pharmacy supply.

Clinical Implications of Treatment Interruption

Adherence to aromatase inhibitor therapy is well established as a determinant of breast cancer outcomes. Multiple prospective studies and retrospective cohort analyses have demonstrated that poor adherence to anastrozole — defined as medication possession ratio below 80% — is associated with significantly higher rates of breast cancer recurrence and breast cancer-specific mortality. For your patients on adjuvant anastrozole therapy, even a brief interruption in access can translate to treatment gaps with real clinical consequences.

Key considerations:

Anastrozole's mechanism requires sustained suppression of serum estradiol levels; temporary discontinuation allows partial recovery of estrogen concentrations within days

Adherence counseling and proactive refill planning can mitigate the majority of pharmacy-level supply disruptions before they become treatment interruptions

Document any supply-related treatment interruptions in the patient's chart for continuity of care and future treatment decisions

Therapeutic Substitution Options

When anastrozole is temporarily unavailable and cannot be sourced through alternative channels, consider switching to another aromatase inhibitor. The following options are appropriate for most postmenopausal patients on adjuvant or metastatic anastrozole therapy:

Letrozole (Femara/generic): 2.5 mg orally once daily. The most pharmacologically similar alternative — both are non-steroidal, reversible aromatase inhibitors. Head-to-head data from the FACE trial and BIG 1-98 suggest comparable outcomes, with some data favoring letrozole in node-positive disease. The switch requires no washout period.

Exemestane (Aromasin/generic): 25 mg orally once daily with food. A steroidal aromatase inactivator — distinct mechanism but equivalent clinical indication. Appropriately substituted in patients who have completed 2–3 years of tamoxifen as sequential adjuvant therapy, or as a direct switch from anastrozole when supply is unavailable. Must be taken with food.

Tamoxifen: NOT an appropriate short-term substitute for anastrozole during a supply interruption. Tamoxifen cannot be administered concurrently with anastrozole and has inferior efficacy in postmenopausal patients compared to aromatase inhibitors. Consider only for patients who have contraindications to all aromatase inhibitors.

Bone Health Considerations When Switching

All aromatase inhibitors reduce bone mineral density. Some comparative data suggest that exemestane may have a slightly more favorable bone density profile than anastrozole in certain patient populations, though the clinical significance remains debated. For patients who have pre-existing osteopenia or osteoporosis, bone density monitoring schedules and concurrent bisphosphonate or denosumab therapy should be maintained regardless of which aromatase inhibitor is prescribed.

Proactive Prescribing Strategies

To protect your patients from supply-related treatment interruptions, consider implementing these best practices in your practice:

Write 90-day prescriptions for stable patients on maintenance aromatase inhibitor therapy to reduce refill frequency and exposure to stock issues

Encourage mail-order enrollment through the patient's insurance plan, which typically offers better pricing and more reliable stock than retail pharmacies

Instruct patients to refill early — at 7–10 days of remaining supply rather than at depletion

Keep samples on hand if possible — even a 7–14 day bridge supply can prevent a treatment interruption while the patient locates stock

Refer patients to medfinder when they report stock difficulties — the service calls pharmacies in the patient's area to locate available stock and texts the patient results, reducing the burden on both patients and office staff

Patient Communication Guidance

When patients contact your office about anastrozole supply issues, a structured response protocol saves time and ensures consistent care:

Confirm how many days of medication remain.

If >5 days remain: recommend medfinder or other pharmacy search tools to locate stock in their area.

If ≤5 days remain: schedule a brief telehealth or phone visit; consider bridge samples or a bridging prescription for letrozole or exemestane.

Document any supply-related gap in treatment and reassess when supply is restored.

How medfinder Supports Oncology Practices

medfinder is a service that calls pharmacies near your patient to check which ones can fill their prescription. Patients provide their medication, dose, and location — medfinder contacts nearby pharmacies and texts results back. This offloads a time-consuming patient support task from your front desk while ensuring patients get actionable information quickly. Learn more at medfinder.com/providers or see our guide on how to help your patients find anastrozole in stock.