Letrozol Ratiopharm (Letrozole)

Letrozole is used in the hormonal management of breast cancer, targeting estrogen‑dependent disease pathways.

• Postmenopausal breast cancer: reduces estrogen production to slow tumor growth and improve progression‑free survival.
• Hormone receptor‑positive early‑stage breast cancer (adjuvant setting): helps prevent disease recurrence after surgery.
• Metastatic hormone‑receptor‑positive breast cancer: provides systemic control when disease has spread beyond the breast.

• Letrozole acts as a reversible, non‑steroidal inhibitor of the aromatase enzyme (CYP19A1). By binding to the enzyme’s heme group, it blocks the conversion of androstenedione and testosterone into estrone and estradiol, respectively. This reduction in peripheral estrogen synthesis lowers circulating estrogen levels, depriving estrogen‑dependent tumor cells of a growth stimulus. The effect is dose‑dependent and persists for several days after the last dose due to the drug’s long half‑life.

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

Common Side Effects

• Hot flashes: sudden feeling of warmth and sweating.
• Joint and muscle pain: arthralgia and myalgia.
• Fatigue: persistent tiredness.
• Nausea: mild to moderate upset stomach.
• Headache: occasional throbbing pain.

Serious or Rare Side Effects

• Severe liver injury: jaundice, elevated enzymes.
• Pulmonary embolism: sudden shortness of breath, chest pain.
• Bone fracture: increased risk due to lowered estrogen.
• Allergic reaction: rash, swelling, anaphylaxis.

When prescribing Letrozole, clinicians should observe several safety considerations.

• Pregnancy contraindication: avoid use in pregnant women; drug is teratogenic (Category X).
• Liver function monitoring: assess hepatic enzymes before and during therapy.
• Bone health assessment: evaluate bone mineral density and consider calcium/vitamin D supplementation.
• Cardiovascular risk: monitor lipid profile and blood pressure in patients with existing heart disease.
• Drug interactions: review concomitant medications that affect CYP2A6 or CYP3A4 activity.
• Store at ambient temperature: keep below 25 °C in the original container, protect from moisture and light.

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

Major Interactions (Avoid)

• Strong CYP2A6 inhibitors (e.g., fluvoxamine): may increase Letrozole plasma levels.
• Potent CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): can raise exposure and risk of toxicity.
• Estrogen‑containing hormone therapy: antagonizes Letrozole’s aromatase inhibition.

Moderate Interactions (Monitor Closely)

• Moderate CYP3A4 inhibitors (e.g., erythromycin, clarithromycin): may modestly increase Letrozole concentrations.
• Warfarin: potential alteration of anticoagulant effect; monitor INR.
• Glucocorticoids: may affect bone density when combined; observe for osteoporosis.