Exemestane

Overview

Exemestane is a hormone therapy drug classified as an aromatase inhibitor. It works by permanently blocking the enzyme aromatase, which the body uses to convert androgens into estrogen, thereby lowering estrogen levels. This reduction in estrogen can slow or stop the growth of estrogen receptor-positive breast cancers, which depend on estrogen to grow. Exemestane is primarily used in postmenopausal women, especially those who have already undergone treatment with tamoxifen, to treat early-stage or advanced breast cancer. It is also under investigation for other cancer types. Traditionally, it has been used since the early 2000s as a targeted therapy to reduce hormone-driven tumor growth in breast cancer patients after menopause.¹²

Forms and Variations

Exemestane is available exclusively as oral tablets, commonly under the brand name Aromasin. The tablets are designed for once-daily administration and are typically swallowed whole with water after a meal to optimize absorption. There are no widely used alternative formulations such as injections or extended-release forms. The choice of exemestane tablets is due to their effective bioavailability and ease of use in outpatient settings. No significant variations in the chemical form exist commercially, but dosing may be adjusted based on clinical factors.²⁴

Dosage and Administration

The standard recommended dose of exemestane is 25 mg once daily, taken orally after a meal to enhance absorption. It is important to take the medication at the same time each day to maintain consistent blood levels. Treatment duration often extends for several years, especially in the adjuvant setting after tamoxifen therapy, to reduce the risk of cancer recurrence. Patients are advised to follow their healthcare provider"s instructions carefully and not to alter the dose or stop treatment without medical consultation. If a dose is missed, patients should take it as soon as possible unless it is near the time for the next dose.³²

Scientific Research and Mechanism of Action

Exemestane acts by irreversibly binding to and inactivating the aromatase enzyme, which catalyzes the conversion of androgens to estrogens in peripheral tissues such as fat, muscle, and skin. This inhibition leads to a significant reduction in circulating estrogen levels in postmenopausal women, depriving estrogen receptor-positive breast cancer cells of the hormone needed for their growth. Clinical trials have demonstrated that exemestane effectively reduces the risk of breast cancer recurrence and slows progression in advanced cases. Research also shows that exemestane may have a steroidal structure, differentiating it from nonsteroidal aromatase inhibitors, which may influence its side effect profile and resistance patterns. Current studies continue to explore its use in combination therapies and in other hormone-sensitive cancers.¹²⁵

Benefits and Potential Uses

Exemestane is primarily used to treat early and advanced estrogen receptor-positive breast cancer in postmenopausal women, especially after tamoxifen therapy. It helps reduce estrogen levels, thereby slowing or stopping tumor growth and lowering the risk of cancer recurrence. It is effective in hormone-sensitive tumors that rely on estrogen for proliferation. Beyond breast cancer, exemestane is being studied for potential use in other hormone-driven cancers, although these applications are not yet standard. Its benefits include improved survival rates and delayed disease progression in appropriate patients. Additionally, exemestane may be used in extended adjuvant therapy to maintain remission.¹³

Side Effects and Risks

Common side effects of exemestane include hot flashes, fatigue, joint pain, headache, and increased sweating. Because it lowers estrogen, it may also cause bone thinning (osteoporosis) and increase fracture risk. Other potential risks include nausea, dizziness, and increased cholesterol levels. Women with pre-existing osteoporosis or cardiovascular disease should use caution. Exemestane is contraindicated in premenopausal women and during pregnancy due to its estrogen-lowering effects. Patients should be monitored for bone density and cardiovascular health during treatment.⁴³

Interactions and Precautions

Exemestane may interact with drugs that affect liver enzymes, potentially altering its metabolism. Caution is advised when used with hormone replacement therapy or other estrogen-containing medications, as these can counteract its effects. It is important to inform healthcare providers of all medications and supplements being taken. Exemestane should be used with caution in patients with liver impairment. Women who are pregnant or breastfeeding should avoid exemestane. Prior to surgery or medical procedures, patients should inform their doctors about exemestane use due to potential effects on healing and bone health.³⁴

Impact on Biomarkers

Exemestane significantly lowers circulating estrogen levels, including estradiol and estrone, which can be measured in blood tests. It may also influence bone turnover markers due to its effect on bone metabolism. Monitoring lipid profiles is recommended as exemestane can increase cholesterol levels. These biomarker changes reflect its mechanism of action and help guide therapy and safety monitoring.¹⁴

Overdose and Toxicity

Overdose of exemestane is rare but may increase the risk of severe side effects such as profound estrogen depletion symptoms, including severe hot flashes, bone pain, and fatigue. There is no established antidote; treatment is supportive. The safe upper limit is not well defined, but doses above the prescribed 25 mg daily are not recommended. Patients should adhere strictly to prescribed dosing and seek immediate medical attention if overdose is suspected.³

Disclaimer

The information provided in this document is for educational purposes only and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.