Letrozole Synthon (Letrozole)

Letrozole is an aromatase inhibitor used in the management of estrogen‑dependent breast cancer.

• Early‑stage hormone receptor‑positive breast cancer in postmenopausal women: reduces risk of disease recurrence when given as adjuvant therapy.
• Metastatic hormone receptor‑positive breast cancer in postmenopausal women: delays disease progression as first‑line endocrine therapy.
• Neoadjuvant treatment of hormone receptor‑positive breast cancer: may shrink tumor size before surgery.

• Letrozole reversibly binds to the aromatase enzyme, a cytochrome P450 isoform responsible for converting androgens to estrogens. By non‑competitive inhibition, it markedly lowers circulating estrogen levels, depriving estrogen‑dependent tumor cells of growth stimulus and thereby inhibiting proliferation of hormone‑sensitive breast cancer cells.

Adverse reactions may occur with letrozole therapy.

Common Side Effects

• Hot flashes: sudden feeling of warmth, often with sweating.
• Joint pain: aching or stiffness in joints.
• Fatigue: persistent tiredness not relieved by rest.
• Nausea: sensation of queasiness, sometimes leading to vomiting.

Serious or Rare Side Effects

• Severe liver injury: jaundice, elevated liver enzymes, hepatic failure.
• Bone fracture: increased risk due to reduced estrogen protection of bone.
• Pulmonary embolism: sudden shortness of breath, chest pain, possible circulatory compromise.

Patients should be monitored for specific safety considerations while on letrozole.

• Bone health monitoring: assess bone mineral density periodically.
• Liver function assessment: perform baseline and periodic liver enzyme tests.
• Cardiovascular risk evaluation: monitor blood pressure and lipid profile.
• Pregnancy avoidance: contraindicated in pregnancy; ensure effective contraception.
• Caution with estrogen therapy: avoid concurrent use of estrogen‑containing products.
• Store at room temperature: keep in original container, protect from moisture and direct sunlight.

Letrozole may interact with other medicines, altering its efficacy or safety.

Major Interactions (Avoid)

• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce letrozole plasma levels and effectiveness.
• Concurrent estrogen‑containing hormone therapy: antagonizes letrozole’s estrogen‑lowering action.

Moderate Interactions (Monitor Closely)

• Selective serotonin reuptake inhibitors (e.g., fluoxetine): may modestly increase letrozole concentrations.
• Warfarin: potential alteration of anticoagulant effect; monitor INR.
• Cholesterol‑lowering agents (e.g., statins): observe for any unexpected changes in lipid profile.