Letromyl (Letrozole)

Letromyl, an aromatase inhibitor, is used in breast‑cancer treatment pathways that depend on estrogen suppression.

• Hormone‑receptor positive breast cancer (postmenopausal): reduces tumor growth and recurrence.
• Adjuvant therapy: helps prevent disease return after surgical removal of the tumour.
• Neoadjuvant therapy: shrinks tumours before surgery to enable breast‑conserving procedures.
• Metastatic disease: controls progression in advanced hormone‑sensitive breast cancer.

• Letrozole reversibly binds to the aromatase enzyme, blocking the conversion of androgens to estrogens in peripheral tissues. By lowering circulating estrogen levels, it deprives estrogen‑dependent tumour cells of a growth stimulus, thereby inhibiting proliferation of hormone‑sensitive breast cancer cells.

Letrozole may cause a range of adverse reactions, most of which are mild to moderate in severity.

Common Side Effects

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

Serious or Rare Side Effects

• Severe liver injury: jaundice, dark urine, elevated enzymes.
• Bone fracture: increased risk due to reduced bone density.
• Pulmonary embolism: sudden shortness of breath, chest pain.
• Allergic reaction: rash, swelling, or anaphylaxis.
• QT interval prolongation: potential cardiac arrhythmia.
• Severe hypertension: markedly high blood pressure.

Before initiating Letromyl therapy, clinicians should consider several safety measures.

• Monitor liver function: obtain baseline tests and repeat periodically.
• Assess bone health: supplement calcium and vitamin D, consider bone‑density scanning.
• Evaluate cardiovascular risk: check blood pressure and lipid profile.
• Avoid use in pregnancy: drug is contraindicated for women who are or may become pregnant.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Letrozole can interact with other medicines, altering its effectiveness or safety.

Major Interactions (Avoid)

• Tamoxifen: concurrent use may antagonize therapeutic effect.
• Strong CYP3A4 inducers (e.g., rifampin): may reduce letrozole plasma levels.
• Strong CYP3A4 inhibitors (e.g., ketoconazole): may increase exposure and toxicity.

Moderate Interactions (Monitor Closely)

• Anticoagulants (e.g., warfarin): may enhance bleeding risk.
• Corticosteroids: may exacerbate bone loss.
• Selective serotonin reuptake inhibitors: may increase risk of hyponatremia.