Leoncon (Letrozole)

Letrozole is an aromatase inhibitor used in the hormonal management of breast cancer.

• Hormone receptor‑positive breast cancer in postmenopausal women: reduces estrogen production to slow tumor progression.
• Adjuvant therapy for early‑stage disease: decreases risk of cancer recurrence after surgery.
• Metastatic breast cancer: helps control disease spread by limiting estrogen‑driven tumor growth.

• Letrozole reversibly binds to the aromatase enzyme, inhibiting its activity in peripheral tissues. This blockade prevents the conversion of androgens (androstenedione and testosterone) into estrogens (estrone and estradiol), leading to markedly reduced circulating estrogen levels and diminished estrogen‑driven tumor proliferation in hormone‑sensitive breast cancer.

Letrozole may cause a range of adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Hot flashes: sudden feeling of warmth, often with sweating.
• Joint and muscle pain: aching or stiffness in joints and muscles.
• Fatigue: persistent tiredness not relieved by rest.
• Nausea: mild to moderate upset stomach.
• Headache: pressure or throbbing pain in the head.
• Increased sweating: excessive perspiration.

Serious or Rare Side Effects

• Severe liver injury: jaundice, elevated liver enzymes.
• Deep vein thrombosis or pulmonary embolism: blood clots in veins or lungs.
• Bone fractures: increased risk due to reduced estrogen.
• Allergic reactions: rash, itching, swelling, or anaphylaxis.
• Elevated cholesterol levels: may worsen cardiovascular risk.
• Severe hypertension: markedly high blood pressure.

Before initiating Letrozole therapy, clinicians should consider several safety measures.

• Liver function monitoring: assess baseline enzymes and repeat periodically.
• Bone health assessment: evaluate bone mineral density and consider supplementation.
• Cardiovascular risk evaluation: review history of thrombosis or hypertension.
• Pregnancy avoidance: Letrozole is contraindicated in pregnancy (Category X).
• Osteoporosis caution: avoid in patients with severe bone loss unless benefits outweigh risks.
• Store at ambient temperature: keep in the original container, protect from moisture and heat.

Letrozole can interact with other medicines, requiring attention to avoid reduced efficacy or increased toxicity.

Major Interactions (Avoid)

• Tamoxifen: concurrent use may antagonize Letrozole’s anti‑estrogen effect.
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): can markedly lower Letrozole plasma levels.
• Anticoagulants (e.g., warfarin): may increase bleeding risk.

Moderate Interactions (Monitor Closely)

• SSRIs (e.g., fluoxetine): may exacerbate hot flashes.
• Statins: potential for increased myopathy risk.
• Hormone replacement therapy: may counteract Letrozole’s estrogen suppression.