Letrozol Sun (Letrozole)

Letrozol Sun is an aromatase inhibitor used in the management of hormone‑dependent breast cancer.

• Early‑stage hormone receptor‑positive breast cancer: reduces risk of recurrence when given as adjuvant therapy.
• Metastatic hormone receptor‑positive breast cancer: slows disease progression in postmenopausal patients.
• Postmenopausal estrogen suppression: supports endocrine therapy by lowering systemic estrogen levels.

• Letrozole is a selective, non‑steroidal inhibitor of the aromatase enzyme, which converts androstenedione and testosterone to estrone and estradiol. By binding to the aromatase active site, it blocks estrogen synthesis, leading to markedly reduced circulating estrogen concentrations and thereby limiting estrogen‑driven tumor proliferation in hormone‑sensitive breast cancer.

Adverse reactions may occur with Letrozol Sun and are categorized by frequency.

Common Side Effects

• Hot flashes: sudden feeling of warmth, often with sweating.
• Joint and muscle pain: arthralgia or myalgia.
• Fatigue: persistent tiredness.
• Nausea: mild to moderate upset stomach.
• Headache: occasional throbbing pain.
• Increased sweating: excessive perspiration.

Serious or Rare Side Effects

• Severe liver injury: jaundice, elevated enzymes.
• Bone fracture: increased risk due to reduced estrogen.
• Deep vein thrombosis or pulmonary embolism: signs of clot formation.
• Allergic reaction: rash, itching, swelling.
• Elevated cholesterol: dyslipidemia.
• Severe hypertension: markedly high blood pressure.

Before initiating Letrozol Sun, clinicians should consider several safety measures.

• Monitor bone mineral density: assess risk of osteoporosis and consider supplementation.
• Assess liver function: obtain baseline tests and repeat periodically.
• Evaluate cardiovascular risk: review history of thromboembolic events.
• Avoid use in pregnancy: drug is contraindicated in pregnant women.
• Store at ambient temperature below 25°C: keep in the original pack, protect from moisture.

Letrozol Sun may interact with other medicines; awareness of interaction severity is essential.

Major Interactions (Avoid)

• Tamoxifen: concurrent use reduces the efficacy of both agents.
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): may lower letrozole plasma concentrations.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): may increase letrozole exposure and toxicity.

Moderate Interactions (Monitor Closely)

• Anticoagulants such as warfarin: may enhance anticoagulant effect and raise INR.
• CYP2C19 inhibitors (e.g., fluoxetine, fluvoxamine): may affect letrozole metabolism.
• Hormone replacement therapy: may alter estrogen levels and affect therapeutic outcomes.