Letrozol Tarbis (Letrozole)

• Letrozole is used in the management of hormone‑dependent breast cancer, specifically targeting estrogen‑driven disease.
• Hormone receptor‑positive breast cancer in postmenopausal women: reduces estrogen levels to inhibit tumor growth.

• Letrozole selectively binds to the aromatase enzyme in peripheral tissues, blocking the conversion of androgens (androstenedione and testosterone) into estrogens (estrone and estradiol). This inhibition markedly lowers circulating estrogen concentrations, depriving estrogen‑dependent cancer cells of a growth stimulus and thereby limiting tumor proliferation.

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

Common Side Effects

• Hot flashes: sudden feeling of warmth and sweating.
• Arthralgia: joint pain or stiffness.
• Nausea: mild to moderate upset stomach.
• Fatigue: persistent tiredness.
• Headache: mild to moderate pain.
• Insomnia: difficulty falling or staying asleep.

Serious or Rare Side Effects

• Severe liver injury: jaundice, elevated enzymes.
• Bone fractures: increased risk due to reduced bone density.
• Pulmonary embolism: sudden shortness of breath, chest pain.
• Myocardial infarction: heart attack symptoms.
• Anaphylaxis: severe allergic reaction with swelling and difficulty breathing.
• Stevens‑Johnson syndrome: severe skin rash and blistering.

• When prescribing Letrozole, clinicians should consider several safety precautions to minimize risk.
• Pregnancy contraindication: drug is classified as Category X and must not be used during pregnancy.
• Bone health monitoring: assess bone mineral density because estrogen depletion can increase fracture risk.
• Liver function: evaluate hepatic enzymes before initiation and periodically during therapy.
• Cardiovascular risk: monitor for signs of thromboembolic events, especially in patients with pre‑existing risk factors.
• Drug interactions: review concomitant medications that affect CYP2A6 or CYP3A4 metabolism.
• Store at ambient temperature: keep below 25 °C in the original container, protect from moisture and light.

Letrozole interacts with several medicines that can alter its effectiveness or increase toxicity.

Major Interactions (Avoid)

• Estrogen‑containing hormone therapy: antagonizes Letrozole’s estrogen‑lowering effect.
• Strong CYP2A6 inhibitors (e.g., fluvoxamine, methoxsalen): may increase Letrozole plasma concentrations.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): can raise drug levels.

Moderate Interactions (Monitor Closely)

• CYP3A4 inducers (e.g., rifampin, carbamazepine): may reduce Letrozole exposure.
• Warfarin: Letrozole may enhance anticoagulant effect; monitor INR.
• SSRIs or other serotonergic agents: potential for additive side effects such as nausea.