Lametta (Letrozole)

Letrozole is used in the hormonal management of breast cancer, targeting estrogen‑dependent tumor growth.

• Hormone receptor‑positive breast cancer (adjuvant): Reduces risk of recurrence after surgery in postmenopausal women.
• Metastatic breast cancer (postmenopausal): Delays disease progression by suppressing estrogen‑driven tumor growth.
• Locally advanced breast cancer (postmenopausal): Shrinks tumors to facilitate surgical intervention.

• Letrozole selectively binds to the aromatase enzyme (CYP19A1) in peripheral tissues, inhibiting the conversion of androstenedione and testosterone to estrone and estradiol. This profound reduction in circulating estrogen deprives estrogen‑dependent breast cancer cells of a growth stimulus, leading to decreased tumor proliferation and potential regression. The inhibition is reversible and highly selective, with minimal impact on other cytochrome P450 enzymes, allowing targeted estrogen suppression without significant alteration of cortisol or aldosterone pathways.

Letrozole may be associated with a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Hot flashes: Sudden feeling of warmth, often with sweating and flushing.
• Fatigue: Persistent lack of energy or tiredness that may affect daily activities.
• Nausea: Mild to moderate upset stomach, sometimes accompanied by loss of appetite.
• Arthralgia: Joint pain or stiffness, commonly affecting knees, hips or hands.

Serious or Rare Side Effects

• Severe liver injury: Jaundice, markedly elevated liver enzymes, or hepatic failure requiring medical attention.
• Pulmonary embolism: Sudden shortness of breath, chest pain, or coughing up blood, a medical emergency.
• Bone fracture: Increased risk of osteoporosis leading to fractures, especially in the spine or hip.
• Anaphylaxis: Rapid onset of swelling, hives, and difficulty breathing, needing immediate treatment.

When prescribing Letrozole, several precautions should be observed to ensure patient safety.

• Pregnancy contraindication: Not to be used in pregnant women; teratogenic (Category X).
• Breastfeeding restriction: Discontinue treatment; drug may pass into milk.
• Bone health monitoring: Assess bone mineral density regularly due to risk of osteoporosis.
• Hepatic function: Use with caution in patients with severe liver impairment; monitor liver enzymes.
• Cardiovascular assessment: Evaluate for history of thromboembolic events before initiating therapy.
• Store at ambient temperature: Keep below 25°C in the original container, protect from moisture and direct sunlight.

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

Major Interactions (Avoid)

• Tamoxifen: Opposes aromatase inhibition, reducing therapeutic benefit.
• Estrogen replacement therapy: Counteracts estrogen suppression, diminishing efficacy.
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): Decrease plasma levels of letrozole.

Moderate Interactions (Monitor Closely)

• Warfarin: May enhance anticoagulant effect; monitor INR.
• SSRIs (e.g., fluoxetine): Potential to alter hormone metabolism; observe clinical response.
• Cholesterol‑lowering agents (e.g., statins): Possible additive hepatic load; check liver function tests.
• Other aromatase inhibitors: Combined use may increase toxicity; avoid unless clinically justified.