COMMON TRADE NAME(S): Aromasin®
Exemestane is a potent and irreversible steroidal aromatase inactivator. It inhibits the conversion of adrenally generated androstenedione to estrone by aromatase in peripheral tissues, such as adipose tissue as well as in tumours.Exemestane does not affect the synthesis of adrenal corticosteroid, aldosterone, or thyroid hormone.
Exemestane is distributed extensively into tissue.
Exemestane is extensively (90%) metabolized in the liver by cytochrome P450 isoenzyme 3A4 and aldoketoreductases.
Metabolites are excreted equally in the urine and feces.
Not applicable
The following table contains adverse effects reported in > 5% of postmenopausal patients with early breast cancer in sequential adjuvant clinical trials.It also includes severe, life-threatening, or post-marketing adverse events from other sources.
* "Incidence" may refer to an absolute value or the higher value from a reported range. "Rare" may refer to events with < 1% incidence, reported in post-marketing, phase 1 studies, isolated data or anecdotal reports.
** I = immediate (onset in hours to days) E = early (days to weeks) D = delayed (weeks to months) L = late (months to years)
The most common side effects for exemestane include estrogen deprivation symptoms, musculoskeletal pain, fatigue, ↑ LFTs, alopecia, headache, insomnia, hypertension and dizziness.
Severe rash, usually early, including erythema multiforme and acute generalized exanthematus pustulosis (AGEP) has been reported.
As compared with megestrol acetate in advanced breast cancer, exemestane produced fewer side effects, including less weight gain, but caused more hot flashes, depression, insomnia, dizziness, anorexia, nausea, and vomiting. As compared to tamoxifen in early breast cancer, exemestane had higher incidences of fatigue, headache, hot flashes, musculoskeletal and nervous system disorders, osteoporosis, (± fractures), hypercholesterolemia, cardiovascular events, ↑ LFTs and ↑ creatinine.
Patients treated with aromatase inhibitors may be at a higher risk for cardiovascular events as well as osteoporosis.
Refer to protocol by which patient is being treated.
Assess patient’s risk factors for osteoporosis and consider calcium and vitamin D supplements and bisphosphonates where appropriate.
Oral: 25 mg Daily
Although AUC is tripled in the presence of liver impairment (Child-Pugh C), adverse effects are not increased. No dosage adjustment is required.
Although AUC is tripled in the presence of severe renal impairment (CrCl < 30 mL/min), adverse effects are not increased. No dosage adjustment is required.
No dosage adjustment is required.
Safety and efficacy not established.
*not receiving ovarian suppression
Exemestane is metabolized by cytochrome P450 CYP 3A4 and aldoketoreductases.It does not inhibit any of the major CYP isoenzymes, including CYP1A2, 2C9, 2D6, 2E1, and 3A.
CYP3A4 inhibition (e.g. ketoconazole) showed no significant effect on exemestane pharmacokinetics.
CYP3A4 induction (e.g. rifampin) produced pharmacokinetic effects but did not affect the suppression of plasma estrogen concentrations.No dose adjustment is required.
Treating physicians may decide to monitor more or less frequently for individual patients but should always consider recommendations from the product monograph.
Grade toxicity using the current NCI-CTCAE (Common Terminology Criteria for Adverse Events) version.
Clemett D, Lamb H. Exemestane: a review of its use in postmenopausal women with advanced breast cancer.Drugs 2000 Jun; 59(6): 1279-96.
Prescribing Information: Aromasin® (exemestane). Pfizer Inc (USA). May 2018.
Product Monograph: Aromasin® (exemestane).Pfizer Canada Inc.March 6, 2018.
August 2025 Updated Pregnancy/Lactation section
Refer to the New Drug Funding Program or Ontario Public Drug Programs websites for the most up-to-date public funding information.
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