Letmylan (Letrozole)

Letrozole is an aromatase inhibitor used in the management of estrogen‑dependent breast cancer. It works by lowering circulating estrogen levels in postmenopausal patients.

• Hormone receptor‑positive breast cancer (postmenopausal): reduces tumor growth by decreasing estrogen synthesis.
• Adjuvant therapy for early‑stage breast cancer (postmenopausal): lowers the risk of disease recurrence after surgery.
• Metastatic breast cancer (postmenopausal): helps control disease progression and prolongs survival.

• Letrozole selectively inhibits the aromatase enzyme, which converts androgens to estrogens in peripheral tissues. By blocking this conversion, systemic estrogen concentrations fall, depriving estrogen‑dependent tumor cells of a growth stimulus and thereby slowing or halting cancer progression.

Adverse reactions may vary in frequency and severity. Patients should be monitored regularly for any new or worsening symptoms.

Common Side Effects

• Hot flashes: sudden feeling of warmth, often with sweating.
• Joint pain: aching or stiffness in knees, hips, or shoulders.
• Fatigue: persistent tiredness not relieved by rest.
• Nausea: mild to moderate upset stomach.
• Headache: pressure or throbbing sensation.
• Sweating: increased perspiration, especially at night.

Serious or Rare Side Effects

• Severe liver injury: jaundice, dark urine, abdominal pain.
• Bone fracture: increased risk due to reduced bone mineral density.
• Pulmonary embolism: sudden shortness of breath, chest pain.
• Allergic reaction: rash, itching, swelling, or difficulty breathing.
• Elevated cholesterol: changes in lipid profile requiring monitoring.
• QT interval prolongation: potential cardiac arrhythmia.

Before initiating therapy, clinicians should assess individual risk factors and monitor patients throughout treatment.

• Bone health monitoring: perform baseline bone density scans and consider calcium/vitamin D supplementation.
• Liver function assessment: check hepatic enzymes prior to start and periodically thereafter.
• Cardiovascular evaluation: review history of thrombosis or hyperlipidaemia.
• Pregnancy avoidance: contraindicated in pregnant or nursing women; ensure effective contraception.
• Drug interaction review: verify concomitant medications that may affect letrozole metabolism.
• Store at room temperature: keep in original packaging, protect from moisture and direct sunlight.

Letrozole may interact with several medicines that influence its metabolism or therapeutic effect.

Major Interactions (Avoid)

• Tamoxifen: concurrent use may reduce efficacy of both agents.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): can increase letrozole plasma levels.
• Estrogen‑containing hormone therapy: antagonizes letrozole’s aromatase inhibition.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampicin, carbamazepine): may lower letrozole concentrations.
• Warfarin: potential alteration of anticoagulant effect; monitor INR.
• Statins: possible increased risk of muscle toxicity; observe for myalgia.
• SSRIs/SNRIs: may affect hormonal balance; assess clinical response.