Letrozole Novumgen (Letrozole)

Letrozole is used in the management of hormone‑dependent breast cancer, acting by suppressing estrogen synthesis.

• Hormone receptor‑positive breast cancer (adjuvant setting): lowers the risk of disease recurrence after primary surgery.
• Hormone receptor‑positive breast cancer (metastatic setting): delays disease progression and extends survival.
• Advanced or locally advanced breast cancer: provides endocrine control when tumors are estrogen‑driven.
• Post‑surgical estrogen suppression: maintains low estrogen levels to support long‑term remission.
• Combination therapy with ovarian suppression in selected premenopausal patients: enhances overall endocrine blockade.

• Letrozole reversibly binds to the aromatase enzyme, inhibiting its activity in peripheral tissues such as adipose and breast tissue. This blockade prevents the conversion of androgens to estrogens, leading to markedly reduced circulating estrogen levels. The resulting hypo‑estrogenic state deprives estrogen‑dependent tumor cells of a growth stimulus, thereby slowing or halting cancer progression.

Letrozole may cause a range of adverse reactions, which vary in frequency and severity.

Common Side Effects

• Hot flashes: sudden feeling of warmth and sweating.
• Joint and muscle pain: aching in limbs and back.
• Fatigue: persistent tiredness not relieved by rest.
• Nausea or mild gastrointestinal upset.
• Headache: pressure or throbbing pain.
• Dizziness or light‑headedness.

Serious or Rare Side Effects

• Severe liver injury: jaundice, dark urine, abdominal pain.
• Bone fractures: increased risk due to reduced bone mineral density.
• Pulmonary embolism: sudden shortness of breath, chest pain.
• Allergic reactions: rash, swelling, difficulty breathing.
• Elevated cholesterol levels: may require monitoring.
• Cardiovascular events: rare cases of heart attack or stroke.

Before initiating Letrozole therapy, clinicians should evaluate patient‑specific risk factors and monitor ongoing safety.

• Bone health assessment: perform baseline densitometry and consider calcium/vitamin D supplementation.
• Liver function monitoring: check hepatic enzymes periodically.
• Cardiovascular risk review: assess history of thrombosis or hyperlipidaemia.
• Pregnancy avoidance: ensure effective contraception; drug is contraindicated in pregnancy.
• Drug interaction check: review concomitant medications for CYP450 modifiers.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Letrozole can interact with several medicines that affect its metabolism or therapeutic effect.

Major Interactions (Avoid)

• Estrogen‑containing products: negate aromatase inhibition and reduce efficacy.
• Strong CYP3A4 inducers (e.g., rifampin, carbamazepine): markedly lower plasma concentrations.
• Strong CYP2C19 inhibitors (e.g., fluconazole): increase exposure and potential toxicity.

Moderate Interactions (Monitor Closely)

• Tamoxifen: may compete for estrogen pathways, requiring efficacy assessment.
• Warfarin: altered anticoagulant effect, monitor INR more frequently.
• Selective serotonin reuptake inhibitors (e.g., fluoxetine): modest impact on metabolism, observe for side‑effect changes.