Letropen (Letrozole)

Letrozole acts on estrogen‑dependent pathways in breast cancer, providing therapeutic benefit in several clinical settings.

• Adjuvant treatment of hormone receptor‑positive early breast cancer: reduces risk of disease recurrence after surgery.
• Advanced or metastatic hormone receptor‑positive breast cancer: delays disease progression in postmenopausal patients.
• Neoadjuvant therapy for breast cancer: shrinks tumor size before definitive surgery, facilitating breast‑conserving procedures.

• Letrozole reversibly binds to the aromatase enzyme, inhibiting its activity and thereby decreasing the peripheral conversion of androgens to estrogens. This reduction in circulating estrogen limits the growth stimulus for estrogen‑dependent tumor cells, particularly in postmenopausal breast cancer.

Letrozole may cause a range of adverse reactions, some of which are common and others that are serious or rare.

Common Side Effects

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

Serious or Rare Side Effects

• Severe liver injury: jaundice, elevated liver enzymes.
• Bone fracture: increased risk due to reduced estrogen.
• Pulmonary embolism: sudden shortness of breath, chest pain.
• Anaphylactic reaction: swelling, hives, difficulty breathing.
• Elevated cholesterol levels: may require monitoring.
• QT interval prolongation: potential cardiac rhythm disturbance.

Before initiating Letrozole, several safety considerations should be reviewed.

• Pregnancy: contraindicated (Category X); teratogenic risk.
• Menopausal status: only indicated for postmenopausal women.
• Bone health: monitor bone mineral density and consider supplementation.
• Liver function: assess hepatic enzymes prior to therapy.
• Drug interactions: review concomitant medications for potential conflicts.
• Store at ambient temperature: keep in original container, protect from moisture and light.

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

Major Interactions (Avoid)

• Estrogen replacement therapy: antagonizes letrozole’s effect.
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): may lower plasma levels.
• Tamoxifen: opposing mechanisms may diminish therapeutic benefit.

Moderate Interactions (Monitor Closely)

• CYP2A6 inhibitors (e.g., fluvoxamine): may increase letrozole exposure.
• Warfarin: potential increase in INR, monitor coagulation.
• SSRIs or other antidepressants: may affect hot‑flash management and require observation.