Letrozol Vir (Letrozole)

Letrozole is an aromatase inhibitor used in the management of estrogen‑dependent breast cancer. It works by lowering estrogen levels that fuel tumor growth.

• Hormone receptor‑positive breast cancer in postmenopausal women: reduces tumor progression and improves survival.
• Adjuvant treatment of early‑stage breast cancer: lowers risk of recurrence after surgery.
• Metastatic breast cancer in postmenopausal patients: controls disease spread and alleviates symptoms.

• Letrozole reversibly binds to the aromatase enzyme, inhibiting its activity and preventing the peripheral conversion of androgens to estrogens. This reduction in estrogen synthesis leads to decreased estrogen stimulation of hormone‑sensitive breast cancer cells, thereby slowing tumor growth and proliferation.

Letrozole may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Hot flashes: transient episodes of increased body temperature.
• Arthralgia: joint pain or stiffness.
• Fatigue: generalized tiredness.
• Nausea: mild to moderate upset stomach.
• Headache: occasional throbbing pain.
• Osteoporosis: decreased bone mineral density with long‑term use.

Serious or Rare Side Effects

• Venous thromboembolism: blood clots in deep veins or lungs.
• Severe liver injury: marked elevation of hepatic enzymes.
• Interstitial lung disease: inflammation of lung tissue.
• Cardiac arrhythmias: irregular heart rhythms.
• Severe allergic reactions: rash, swelling, or breathing difficulty.

Patients should be monitored for specific safety considerations when using Letrozole.

• Pregnancy: contraindicated; letrozole is classified as Pregnancy Category X.
• Breastfeeding: not recommended; may pass into milk and affect the infant.
• Bone health: assess bone mineral density regularly due to risk of osteoporosis.
• Cardiovascular risk: monitor for signs of thrombosis or heart rhythm disturbances.
• Liver function: evaluate hepatic enzymes before and during therapy.
• Drug interactions: review concomitant medications for potential CYP2A6 inhibition.
• Store at ambient temperature: keep below 25 °C, in the original container, protected from moisture and light.

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

Major Interactions (Avoid)

• Strong CYP2A6 inhibitors (e.g., fluvoxamine): may increase letrozole plasma levels.
• Estrogen‑containing therapies (e.g., hormone replacement): counteract letrozole’s action.

Moderate Interactions (Monitor Closely)

• Anticoagulants (e.g., warfarin): may enhance bleeding risk.
• Statins metabolized by CYP3A4: potential for altered lipid‑lowering effect.
• Corticosteroids: may increase risk of bone loss.
• Thyroid hormones: monitor thyroid function tests.
• Anticonvulsants inducing hepatic enzymes: may reduce letrozole effectiveness.