Letrozol Mabo (Letrozole)

Letrozole is an aromatase inhibitor used in hormone‑dependent breast cancer therapy, primarily targeting estrogen‑driven tumor growth in postmenopausal patients.

• Postmenopausal estrogen‑receptor positive breast cancer: decreases peripheral estrogen synthesis, thereby slowing tumor proliferation and improving survival outcomes.
• Adjuvant treatment of early‑stage breast cancer: administered after surgery to lower the chance of cancer returning.
• Metastatic breast cancer: employed to control disease spread in advanced, hormone‑responsive tumors.
• Neoadjuvant therapy for locally advanced breast cancer: used before surgery to shrink tumors and facilitate resection.

• Letrozole acts as a reversible, non‑steroidal inhibitor of the aromatase enzyme, which converts androstenedione and testosterone into estrone and estradiol. By binding to the enzyme’s active site, it blocks estrogen synthesis in peripheral tissues, leading to markedly reduced circulating estrogen levels. This hormonal depletion deprives estrogen‑receptor positive breast cancer cells of a growth stimulus, thereby inhibiting tumor progression.

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

Common Side Effects

• Hot flashes: sudden feeling of warmth and sweating.
• Joint pain: aching or stiffness in joints.
• Fatigue: persistent tiredness.
• Nausea: upset stomach and urge to vomit.
• Headache: mild to moderate head pain.
• Dizziness: sensation of light‑headedness.

Serious or Rare Side Effects

• Severe liver injury: jaundice, elevated enzymes.
• Bone fractures: increased risk of osteoporosis‑related breaks.
• Pulmonary embolism: sudden shortness of breath, chest pain.
• Allergic reactions: rash, swelling, anaphylaxis.
• Elevated cholesterol: significant rise in blood lipid levels.
• QT interval prolongation: cardiac rhythm disturbances.

When prescribing Letrozole, clinicians should observe several safety considerations to minimize risks.

• Pregnancy: contraindicated (Category X); teratogenic risk.
• Bone health: monitor bone mineral density and consider calcium/vitamin D supplementation.
• Liver function: assess hepatic status before initiation and periodically thereafter.
• Cardiovascular risk: evaluate history of thromboembolic events and manage risk factors.
• Drug interactions: review concomitant medications for potential CYP2A6 modulation.
• Store at room temperature below 25°C: keep in original packaging, protect from moisture and direct sunlight.

Letrozole can interact with other medicines, affecting its efficacy or safety.

Major Interactions (Avoid)

• Concurrent estrogen‑containing hormone therapy: antagonizes Letrozole’s estrogen‑lowering effect.
• Strong CYP2A6 inducers (e.g., rifampin, carbamazepine): markedly reduce plasma concentrations.
• Pregnancy: exposure must be avoided due to fetal risk.

Moderate Interactions (Monitor Closely)

• Tamoxifen: may alter metabolic pathways, requiring clinical monitoring.
• Warfarin: Letrozole can increase INR, necessitating dose adjustment.
• Selective serotonin reuptake inhibitors (e.g., fluoxetine): may affect drug metabolism and require observation.