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 BRAND NAMES
 MECHANISM OF ACTION
Many breast cancers have estrogen receptors and growth of these tumors can be stimulated by estrogens. The main source of estrogen is the ovaries in premenopausal women, while in post-menopausal women, the principal source of circulating estrogen (primarily estradiol) is conversion of adrenally-generated androstenedione to estrone by aromatase in peripheral tissues, such as adipose tissue, with further conversion of estrone to estradiol.
Exemestane is an irreversible steroidal aromatase inhibitor, structurally related to the natural substrate androstenedione. It significantly lowers serum estradiol concentrations in postmenopausal women. As less estrogen reaches the cancer cells, they grow more slowly or stop growing altogether. Other aromatase inhibitors include letrozole (Femara®) and Anastrozole (Arimidex®).
- Exemestane is indicated for adjuvant treatment of postmenopausal women with estrogen receptor positive early breast cancer who have received two to three years of tamoxifen and are switched to Exemestane for completion of a total of five consecutive years of adjuvant hormonal therapy.
- Exemestane is indicated for the treatment of advanced breast cancer in postmenopausal women whose disease has progressed following tamoxifen therapy.
Recommended dose in early and advanced breast cancer is 25 mg (One tablet) once daily after a meal.
In postmenopausal women with early breast cancer who have been treated with 2-3 years of tamoxifen, treatment with Exemestane should continue until completion of five years adjuvant hormonal therapy, or until tumour relapse occurs.
For patients with advanced breast cancer, treatment with Exemestane should continue until tumor progression is evident.
- Known hypersensitivity to Exemestane
- Premenopausal women
- pregnancy and lactating
 WARNINGS AND PRECAUTIONS
- Decrease in bone mineral density: Exemestane lowers circulating estrogen levels, so it may cause a reduction in bone mineral density with a possible consequent increased risk of fracture. Consider bone mineral density monitoring.
- Routine assessment of 25 hydroxy vitamin D levels prior to the start of aromatase inhibitor treatment should be considered, due to the high prevalence of severe deficiency associated in women with early breast cancer (EBC). Women with Vitamin D deficiency should receive supplementation with Vitamin D.
- CYP3A4 inducers (Rifampicin, Phenytoin, Carbamazepine, St John’s wort, Phenobarbital): Exemestane is extensively metabolized by CYP3A4, therefore CYP3A4 inducers may significantly decrease exposure to exemestane
 PREGNANCY AND LACTATION
- Pregnancy Category X (US). Exemestane is contraindicated in women who are or may become pregnant. In non-clinical studies in rats and rabbits, exemestane was embryotoxic, fetotoxic, and abortifacient. If Exemestane is used during pregnancy, or if the patient becomes pregnant while receiving this drug, the patient should be apprised of the potential hazard to the fetus and potential risk for pregnancy loss.
- Nursing Mothers: Exemestane is only indicated in postmenopausal women. However, it is not known if Exemestane is excreted in human milk. A decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
 SIDE EFFECTS
Exemestane is generally well tolerated, possible adverse effects include:
- Hot flushes and increased sweating
- Vaginal dryness (Vaginal moisturisers or lubricants can be helpful)
- Nausea and vomiting (these side effects can be relieved by taking your tablet with food)
- Joints pain and stiffness
- Diarrhea or constipation (rarely)
- Hair thinning (alopecia). this side effect is usually mild and the hair grows back at the end of treatment.
- Risk of osteoporosis. Exemestane increases the risk of fracture compared with tamoxifen.
Exemestane is not associated with the estrogen-like adverse/benefit effects of tamoxifen (Tamoxifen blocks the effects of estrogen in breast tissue BUT ACTS LIKE ESTROGEN AGONIST in the uterus and bone: Tamoxifen has been associated with endometrial hyperplasia, fibroids, polyps, and endometrial tumors and may INCREASE bone density)