EXEMESTANE
Clinical safety rating: avoid
Contraindicated (not allowed)
Irreversible steroidal aromatase inhibitor; binds to the substrate-binding site of aromatase, causing permanent inactivation of the enzyme. Reduces estrogen synthesis by inhibiting conversion of androgens to estrogens.
| Metabolism | Hepatic, primarily via CYP3A4 and aldoketoreductases; undergoes oxidation and reduction. Metabolites are inactive or less active. |
| Excretion | Primarily hepatic metabolism (CYP3A4 and aldoketoreductases) with fecal excretion of metabolites (approximately 80-90%) and renal excretion of unchanged drug and metabolites (approximately 10-20%). |
| Half-life | Terminal elimination half-life is approximately 24 hours, supporting once-daily dosing. Steady state is achieved after 7 days. |
| Protein binding | Approximately 90% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Apparent volume of distribution is approximately 5 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral bioavailability is approximately 60% after a single dose, with a high-fat meal increasing absorption (AUC increased by 40%). |
| Onset of Action | Oral administration: onset of estrogen suppression occurs within 24 hours, with maximal suppression achieved after 7 days of daily dosing. |
| Duration of Action | Duration of estrogen suppression persists for 4-6 days after discontinuation, reflecting gradual recovery of aromatase activity. |
25 mg orally once daily after a meal.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for GFR ≥30 mL/min. Insufficient data for GFR <30 mL/min. |
| Liver impairment | Child-Pugh A or B: no dose adjustment necessary. Child-Pugh C: not studied; use with caution. |
| Pediatric use | Safety and efficacy not established; no recommended dosing. |
| Geriatric use | No dose adjustment needed; same as adult dosing, but monitor for adverse effects due to age-related changes. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Estrogen-containing medications should not be used Decreases bone mineral density increasing fracture risk.
| Breastfeeding | Exemestane is excreted into rat milk; no human data on M/P ratio. Due to potential for serious adverse reactions in the breastfed infant (e.g., hormone suppression), breastfeeding is not recommended during therapy and for at least 1 month after the last dose. |
| Teratogenic Risk | Exemestane is contraindicated in pregnancy. Based on its mechanism of action (aromatase inhibition) and animal studies, there is a risk of fetal harm. In the first trimester, exposure may interfere with estrogen-dependent developmental processes. In the second and third trimesters, continued aromatase inhibition could impair fetal organogenesis and growth. Adequate human data are lacking, but the drug should be avoided during pregnancy. |
■ FDA Black Box Warning
None
| Common Effects | Hot flashes |
| Serious Effects |
["Hypersensitivity to exemestane or any of its components","Pregnancy (can cause fetal harm; effective contraception required in women of childbearing potential)","Premenopausal women (not effective; use only in postmenopausal women)"]
| Precautions | ["May cause decreased bone mineral density with increased fracture risk; monitor bone density and consider supplementation with calcium and vitamin D.","May cause lipid abnormalities (increased LDL, decreased HDL); monitor lipid profiles.","Use with caution in patients with hepatic or renal impairment (severe impairment not recommended).","May increase risk of ischemic cardiovascular events in patients with preexisting coronary artery disease."] |
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| Fetal Monitoring | Before initiating therapy, rule out pregnancy with a sensitive test. Advise pregnant women of potential fetal risk. For women of childbearing potential, use effective contraception during treatment and for 1 month after the last dose. No specific fetal monitoring is required if pregnancy occurs; refer to obstetric specialist. |
| Fertility Effects | Exemestane reduces estrogen production, which may impair fertility in premenopausal women by disrupting ovarian function and menstrual cyclicity. In males, exemestane may affect spermatogenesis via estrogen suppression. Fertility may be reversible upon discontinuation. |