Exemestane (Aromasin): Uses, Dosage, Side Effects Guide
Comprehensive guide to exemestane (Aromasin) for treating hormone-receptor-positive breast cancer in postmenopausal women.
Exemestane, sold under the brand name Aromasin, is a third-generation aromatase inhibitor (AI) specifically designed to treat hormone-receptor-positive breast cancer in postmenopausal women. It works by irreversibly binding to and inactivating the aromatase enzyme, which converts androgens into estrogens, thereby drastically reducing estrogen levels in the body. This deprivation starves estrogen-dependent breast cancer cells of the hormone they need to grow and proliferate.
Approved for both early-stage and advanced breast cancer, exemestane is particularly effective after prior tamoxifen therapy. It offers a well-tolerated option across treatment settings, including adjuvant therapy to prevent recurrence, metastatic disease management, and even emerging roles in neoadjuvant settings and prevention for high-risk women.
About exemestane tablets
Exemestane tablets are oral medications typically available in 25 mg strength, taken once daily after a meal to enhance absorption. The recommended dose for both early and advanced breast cancer is one 25 mg tablet daily, as established in clinical trials where this dosage achieved 98% aromatase inactivation and 85-95% suppression of plasma estrogens like estrone, estradiol, and estrone sulfate.
Unlike reversible non-steroidal AIs, exemestane’s steroidal structure allows permanent inactivation of aromatase, potentially reducing cross-resistance with other AIs. This makes it valuable in sequence therapy for progressive disease.
- Form: Oral tablet (25 mg)
- Dosage: 25 mg once daily
- Administration: After a meal; do not crush or chew
- Duration: Typically 2-3 years after tamoxifen (total 5 years adjuvant) or until disease progression in advanced cases
Key facts about exemestane tablets
- Exemestane is for postmenopausal women only; in premenopausal women, it’s off-label with ovarian suppression (e.g., via surgery, radiation, or drugs like goserelin).
- Start time: Effects on estrogen suppression begin within 24 hours, with maximum suppression by day 7.
- Common brand: Aromasin (Pfizer).
- Not chemotherapy: It’s targeted hormone therapy that blocks estrogen production without directly killing cells.
- Storage: Room temperature, away from moisture.
- Alcohol: Limit intake; may worsen hot flashes or dizziness.
When to take exemestane tablets
Take exemestane once daily at the same time, after a meal to improve bioavailability. Consistency aids adherence, crucial for long-term efficacy in preventing recurrence. If a dose is missed, take it as soon as remembered unless close to the next dose—do not double up.
In adjuvant settings, it’s often started after 2-3 years of tamoxifen, completing a 5-year hormone therapy course. Extended use beyond 5 years may be recommended based on risk.
How to take exemestane tablets
Swallow the tablet whole with water. No adjustments needed for mild liver/kidney issues, but consult your doctor for moderate-severe impairment. Grapefruit may interact—avoid.
| Scenario | Dosing Instructions |
|---|---|
| Standard | 25 mg once daily post-meal |
| Missed dose | Take ASAP; skip if near next dose |
| With food | Required for optimal absorption |
| Overdose | Seek emergency help; symptoms include nausea, drowsiness |
Common questions about exemestane tablets
Are exemestane tablets a steroid?
Exemestane has a steroidal structure but is not an anabolic steroid. It’s a selective aromatase inactivator, not promoting muscle growth or masculinization.
Do exemestane tablets interact with other medicines?
Yes, moderate interactions with estrogens, tamoxifen, or drugs affecting CYP3A4 (e.g., ketoconazole). Inform your doctor of all medications.
Can I get exemestane tablets on NHS?
In the UK, yes, prescribed for eligible breast cancer patients via NHS. Availability varies by region and guidelines.
How does exemestane work?
Many breast cancers are hormone-receptor-positive, relying on estrogen for growth. Postmenopause, ovaries stop estrogen production, but peripheral tissues (fat, muscle) produce it via aromatase converting androgens (from adrenals) to estrogens. Exemestane irreversibly inhibits aromatase, slashing circulating estrogens by 85-95%, halting cancer cell proliferation.
This mechanism differs from tamoxifen (SERM that blocks estrogen receptors) or other AIs, offering sequencing benefits.
When is exemestane prescribed?
Exemestane treats:
- Early breast cancer: Adjuvant after 2-3 years tamoxifen in postmenopausal women to reduce recurrence.
- Advanced/metastatic: After antiestrogen failure; first-, second-, or later-line.
- Off-label: Premenopausal with ovarian suppression; prevention in high-risk.
Cautions of exemestane tablets
Avoid if premenopausal without suppression, pregnant/breastfeeding, or with severe liver disease. Monitor bone density; use calcium/vitamin D.
Side effects of exemestane tablets
Generally well-tolerated, similar to other AIs: menopausal symptoms, arthralgia, bone loss. Fewer thromboembolic/gynecological events vs. tamoxifen.
Serious side effects
- Bone fractures/osteoporosis (monitor DEXA scans)
- Cardiovascular events
- Liver enzyme elevation
Common side effects
| Side Effect | Frequency | Management |
|---|---|---|
| Hot flashes | Common | Lifestyle, venlafaxine |
| Joint/muscle pain | Common | Exercise, NSAIDs |
| Fatigue | Common | Rest, activity |
| Insomnia | Common | Sleep hygiene |
| Nausea | Less common | With food |
Report persistent pain, vision changes, or swelling.
Other medicines, food & alcohol
Avoid estrogen-containing products. Limit alcohol to prevent worsening side effects. No major food interactions beyond taking post-meal.
Taking exemestane with other breast cancer medicines
Often sequenced after tamoxifen; combined with everolimus for post-NSAI progression. Not with other AIs simultaneously.
Pregnancy, breastfeeding & fertility while taking exemestane tablets
Category D: May harm fetus—use contraception. Not for breastfeeding. May impair fertility.
Common questions about exemestane tablets
What’s the difference between exemestane and tamoxifen?
Exemestane lowers estrogen production; tamoxifen blocks receptors. Exemestane better post-tamoxifen for recurrence reduction.
Will exemestane make me tired?
Fatigue is common; usually improves. Stay active.
Will I gain weight on exemestane?
Possible but less than tamoxifen; diet/exercise help.
Will exemestane affect my bones?
Yes, increases osteoporosis risk—monitor BMD.
Will exemestane affect my sex life?
May cause vaginal dryness/low libido; lubricants or therapy.
Will I lose my hair taking exemestane?
No significant hair loss, unlike chemo.
Do exemestane tablets affect blood pressure?
Possible hypertension; monitor.
Do exemestane tablets cause hair loss?
Rare thinning, not alopecia.
Do exemestane tablets cause constipation?
Possible; fiber/water help.
Do exemestane tablets cause sickness?
Mild nausea; take with food.
Alternatives for exemestane tablets
| Drug | Type | Use |
|---|---|---|
| Anastrozole (Arimidex) | Non-steroidal AI | Adjuvant/metastatic |
| Letrozole (Femara) | Non-steroidal AI | Similar |
| Tamoxifen | SERM | Initial therapy |
| Fulvestrant | ER degrader | Advanced |
Choice based on resistance, tolerance.
Frequently asked questions
Is Aromasin a chemo drug?
No, it’s hormone therapy.
How long to take exemestane?
5 years adjuvant; longer if high risk.
Does exemestane cause weight gain?
Possible; manageable with lifestyle.
Exemestane vs letrozole?
Similar efficacy; exemestane steroidal, less cross-resistance.
References
- Clinical utility of exemestane in the treatment of breast cancer — NIH/PMC. 2015-06-01. https://pmc.ncbi.nlm.nih.gov/articles/PMC4455847/
- Exemestane (Aromasin): What to Expect, Side Effects, and More — BreastCancer.org. 2025-12-23. https://www.breastcancer.org/treatment/hormonal-therapy/aromasin
- Exemestane (oral route) – Side effects & dosage — Mayo Clinic. Accessed 2026. https://www.mayoclinic.org/drugs-supplements/exemestane-oral-route/description/drg-20063757
- Exemestane (Aromasin): Uses, Side Effects, Alternatives & More — GoodRx. Accessed 2026. https://www.goodrx.com/exemestane/what-is
- Exemestane: New Option for Breast Cancer Prevention — American Health & Drug Benefits. 2011-08-01. https://www.ahdbonline.com/issues/2011/august-2011-vol-4-no-4-special-issue/article-772
- Exemestane (Aromasin) — Breast Cancer Now. Accessed 2026. https://breastcancernow.org/about-breast-cancer/treatment/hormone-endocrine-therapy/exemestane-aromasin
- Highlights of prescribing information – Aromasin — Pfizer. Accessed 2026. https://labeling.pfizer.com/showlabeling.aspx?id=523
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