Letrozol Denk (Letrozole)

• Letrozole is used in endocrine therapy targeting estrogen‑driven breast cancer.
• Postmenopausal estrogen receptor‑positive breast cancer (adjuvant): Reduces risk of recurrence after surgery and improves disease‑free survival.
• Metastatic estrogen receptor‑positive breast cancer: Extends progression‑free survival in advanced disease settings.
• Neoadjuvant therapy for ER‑positive tumors: Shrinks tumor size before definitive surgery.
• High‑risk early‑stage breast cancer: Part of adjuvant regimens to lower recurrence rates.
• Hormone‑responsive breast cancer in postmenopausal women: Provides endocrine control when alternative agents are unsuitable.

• Letrozole binds to the aromatase enzyme and inhibits its activity, preventing the conversion of androstenedione and testosterone into estrone and estradiol. This reduction in peripheral estrogen synthesis lowers circulating estrogen levels, thereby depriving estrogen‑dependent breast cancer cells of a growth stimulus and limiting tumor proliferation.

Letrozole may cause a range of adverse reactions, which are classified by frequency and severity.

Common Side Effects

• Hot flashes: Sudden feeling of warmth, often with sweating.
• Arthralgia: Joint pain or stiffness, especially in the knees and hips.
• Fatigue: Persistent tiredness not relieved by rest.
• Nausea: Mild to moderate upset stomach, sometimes with loss of appetite.
• Headache: Tension‑type or migraine‑like pain.
• Insomnia: Difficulty falling or staying asleep.

Serious or Rare Side Effects

• Severe liver injury: Jaundice, elevated transaminases, or hepatic failure.
• Bone fracture: Increased risk of osteoporosis‑related fractures.
• Deep vein thrombosis or pulmonary embolism: Swelling, pain, or shortness of breath.
• Anaphylaxis: Rapid onset of rash, swelling, and breathing difficulty.
• QT interval prolongation: Potential cardiac arrhythmias.

• When prescribing Letrozole, clinicians should consider several safety measures to minimize risk.
• Bone health monitoring: Assess baseline bone mineral density and consider calcium/vitamin D supplementation.
• Liver function: Perform periodic liver enzyme tests to detect hepatotoxicity.
• Cardiovascular risk: Evaluate history of thromboembolic events before initiating therapy.
• Pregnancy avoidance: Contraindicated in pregnancy; ensure effective contraception in women of childbearing potential.
• Drug interactions: Review concomitant medications for CYP inducers or inhibitors.
• Store at ambient temperature: Keep in the original container, protect from moisture and light.

Letrozole interacts with several drugs that can alter its plasma concentration or therapeutic effect.

Major Interactions (Avoid)

• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): May reduce letrozole exposure and efficacy.
• Estrogen‑containing hormone therapy: Opposes aromatase inhibition and diminishes anticancer effect.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin): May increase letrozole levels, requiring monitoring.
• Warfarin: Potential alteration of anticoagulant effect; monitor INR.
• Tamoxifen: May interfere with metabolic pathways; assess clinical response.