Adjuvant treatment of breast cancer in postmenopausal
women who have estrogen-receptor positive early disease
and who have already received 2–3 yr of tamoxifen
and are then switched to exemestane to complete a
total of 5 yr of adjuvant therapy. Treatment of advanced
postmenopausal breast cancer that has progressed despite
tamoxifen therapy.
Action
Inhibits aromatase, an enzyme responsible for the conversion
of androgen to estrogen. In postmenopausal
women, the primary source of estrogen is androgen.
Decreases circulating estrogen. Therapeutic Effects:
Decreased spread of estrogen-sensitive breast
cancer.
Pharmacokinetics
Absorption: 42% absorbed following oral administration.
Distribution: Extensively distributed.
Metabolism and Excretion: Mostly metabolized
by the liver (CYP3A4 enzyme system); metabolites are
excreted in urine (40%) and feces (40%); 1% excreted
unchanged in urine.
Half-life: 24 hr.
TIME/ACTION PROFILE (suppression of
circulating estrogen)
ROUTE ONSET PEAK DURATION
PO unknown 2–3 days 4–5 days
Contraindications/Precautions
Contraindicated in: Hypersensitivity; Premenopausal
status; OB: Pregnancy (may cause fetal harm); Lactation:
Breast feeding should be avoided.
Use Cautiously in: Rep: Women of reproductive
potential; Pedi: Safety and effectiveness not established.
Adverse Reactions/Side Effects
CNS: fatigue, depression, insomnia. CV: THROMBOEMBOLISM,
hypertension. GI: diarrhea, nausea. GU: endometrial
hyperplasia, uterine polyps. Endo: visual
disturbances. Derm: alopecia, hot flashes,qsweating,
dermatitis. MS: arthralgia, musculoskeletal pain, carpal
tunnel syndrome, muscle cramps, osteoporosis.
Neuro: neuropathy, paresthesia.
Interactions
Drug-Drug: Strong CYP3A4 inducers including
rifampin or phenytoin mayplevels and effectiveness;
qdaily dose to 50 mg once daily. Estrogens can interfere
with action.
Route/Dosage
PO (Adults): 25 mg once daily; Concurrent use with
strong CYP3A4 inducers—50 mg once daily.
Availability (generic available)
Tablets: 25 mg.
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