Mexabrest (Exemestane)

Exemestane is an aromatase inhibitor used in hormone‑dependent breast cancer management.

• Hormone receptor‑positive advanced breast cancer: lowers estrogen levels to inhibit tumor growth.
• Post‑surgical adjuvant therapy in postmenopausal women: reduces risk of cancer recurrence after initial treatment.
• Metastatic breast cancer in postmenopausal patients: helps control disease progression when other endocrine therapies are insufficient.

• Exemestane binds irreversibly to the aromatase enzyme, a cytochrome P450 isoform responsible for converting androstenedione and testosterone to estrone and estradiol. By permanently inactivating aromatase, it markedly decreases peripheral estrogen synthesis, leading to lower circulating estrogen concentrations that limit estrogen‑driven proliferation of breast cancer cells. The inhibition is dose‑dependent and persists for several days after the drug is cleared, allowing once‑daily dosing.

Exemestane may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Hot flashes: sudden intense warmth, often accompanied by sweating and reddening of the skin.
• Joint and muscle pain: aching or stiffness in joints, muscles, or the back that may limit mobility.
• Fatigue: ongoing tiredness that interferes with daily activities and is not relieved by rest.
• Nausea or vomiting: mild to moderate stomach upset that may occur after dosing.

Serious or Rare Side Effects

• Deep vein thrombosis or pulmonary embolism: formation of blood clots in deep veins or lungs, presenting with leg swelling, pain, or shortness of breath.
• Severe liver injury: signs include jaundice, dark urine, elevated liver enzymes, or hepatitis.
• Bone fractures: increased risk of osteoporosis‑related fractures, especially in the hip, spine or wrist.

When prescribing Exemestane, several precautions should be observed to ensure patient safety.

• Cardiovascular risk assessment: evaluate history of thromboembolic events before initiating therapy.
• Bone health monitoring: perform baseline bone mineral density test and consider calcium/vitamin D supplementation.
• Liver function evaluation: check hepatic enzymes prior to treatment and periodically during use.
• Drug interactions review: assess concomitant medications that may affect estrogen levels or liver metabolism.
• Pregnancy and lactation: contraindicated in pregnancy (Category X) and not recommended while breastfeeding.
• Store at ambient temperature: keep tablets below 25 °C in the original container, protected from moisture and light.

Exemestane can interact with other medicines, influencing its effectiveness or safety.

Major Interactions (Avoid)

• Antifungal azoles (e.g., ketoconazole, itraconazole): may increase plasma levels of Exemestane, raising toxicity risk.
• Strong CYP3A4 inducers (e.g., rifampicin, carbamazepine): can reduce Exemestane concentrations, diminishing efficacy.

Moderate Interactions (Monitor Closely)

• Hormone replacement therapy: may counteract estrogen suppression.
• Selective estrogen receptor modulators (e.g., tamoxifen): concurrent use can alter therapeutic outcomes.
• Anticoagulants (e.g., warfarin): monitor INR as estrogen changes may affect clotting risk.