Letrozole Eg (Letrozole)

Letrozole is an aromatase inhibitor used in the treatment of estrogen‑dependent breast cancer.

• Adjuvant therapy for postmenopausal hormone receptor‑positive breast cancer: reduces risk of disease recurrence after surgery.
• Metastatic breast cancer in postmenopausal women: helps control tumor progression and prolongs survival.
• Neoadjuvant therapy for estrogen receptor‑positive breast cancer: may shrink tumors prior to surgical resection.
• Extended adjuvant therapy for high‑risk patients: provides continued estrogen suppression after initial treatment.

• Letrozole acts by reversibly binding to the aromatase enzyme, which converts androstenedione and testosterone into estrone and estradiol. Inhibition of aromatase markedly reduces peripheral estrogen production, leading to lower circulating estrogen levels. This estrogen depletion deprives hormone‑sensitive breast cancer cells of a growth stimulus, thereby inhibiting tumor proliferation and inducing apoptosis. The effect is dose‑dependent and persists as long as the drug is present in systemic circulation.

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

Common Side Effects

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

Serious or Rare Side Effects

• Severe bone loss: increased risk of osteoporosis and fractures.
• Cardiovascular events: hypertension, thromboembolic disease.
• Liver toxicity: elevated transaminases or hepatitis.
• Allergic reactions: rash, pruritus, or anaphylaxis.

When prescribing Letrozole, clinicians should observe several safety considerations.

• Assess bone health: baseline DEXA scan recommended for patients at risk of osteoporosis.
• Monitor liver function: periodic liver enzyme tests are advised.
• Check cardiovascular status: evaluate blood pressure and thrombotic risk before initiation.
• Avoid use in premenopausal women: drug is ineffective unless ovarian suppression is confirmed.
• Inform patients about pregnancy risk: contraception required during treatment and for a defined period after discontinuation.
• Store at ambient temperature: keep tablets in original container, protect from moisture and light.

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

Major Interactions (Avoid)

• Concurrent use of strong CYP2A6 inducers (e.g., rifampin): may reduce Letrozole plasma levels.
• Co‑administration with estrogen‑containing hormone therapy: antagonizes therapeutic effect.

Moderate Interactions (Monitor Closely)

• Tamoxifen: may diminish Letrozole’s aromatase inhibition.
• Anticoagulants (warfarin): increased risk of bleeding; monitor INR.
• CYP2A6 inhibitors (e.g., fluvoxamine): may increase Letrozole exposure.