Letrozolo Teva (Letrozole)

Letrozole is used in endocrine therapy for hormone‑dependent breast cancer, acting on estrogen synthesis pathways.

• Adjuvant treatment of hormone receptor‑positive early breast cancer: reduces risk of disease recurrence after surgery.
• Metastatic hormone receptor‑positive breast cancer: slows tumor progression in postmenopausal patients.
• Neoadjuvant therapy for locally advanced breast cancer: decreases tumor size before surgery.

• Letrozole reversibly binds to the aromatase enzyme, a cytochrome P450 isoform responsible for converting androstenedione and testosterone into estrone and estradiol. By inhibiting this enzymatic step, systemic estrogen levels decline, depriving estrogen‑dependent tumor cells of a growth stimulus and thereby limiting proliferation of hormone‑sensitive breast cancer. The inhibition is dose‑dependent and persists for several days after the last dose, allowing sustained estrogen suppression throughout the treatment cycle.

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

Common Side Effects

• Hot flashes: sudden feeling of warmth, often with sweating and reddening of the skin.
• Joint and muscle pain: aching in joints (arthralgia) and muscles (myalgia) that may limit activity.
• Fatigue: persistent tiredness that interferes with daily tasks.
• Nausea: mild stomach upset, sometimes accompanied by loss of appetite.
• Headache: mild to moderate pain in the head, often transient.
• Insomnia: difficulty falling or staying asleep, leading to daytime drowsiness.

Serious or Rare Side Effects

• Osteoporosis or bone fracture: significant loss of bone mineral density increasing fracture risk.
• Severe liver injury: marked elevation of liver enzymes, hepatitis, or hepatic failure.
• Cardiovascular events: deep vein thrombosis, pulmonary embolism, or other clot‑related complications.
• Allergic reactions: rash, angioedema, or rare anaphylactic response requiring immediate medical attention.

When prescribing Letrozolo Teva, clinicians should consider several precautionary measures to ensure safe use.

• Assess bone health: evaluate baseline bone mineral density and consider calcium/vitamin D supplementation.
• Monitor liver function: perform periodic liver enzyme tests during therapy.
• Check cardiovascular risk: review history of thromboembolic disease before initiating treatment.
• Avoid use in premenopausal women: drug is ineffective unless ovarian suppression is confirmed.
• Counsel on menopausal symptoms: discuss management of hot flashes and joint discomfort.
• Store at ambient temperature: keep below 25 °C in the original container, protect from moisture and direct sunlight.

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

Major Interactions (Avoid)

• Strong CYP3A4 inducers (e.g., rifampicin, carbamazepine): may reduce letrozole plasma concentrations and diminish therapeutic effect.
• Estrogen‑containing hormone therapy (e.g., conjugated estrogens, oral contraceptives): counteracts aromatase inhibition and can increase estrogen levels.
• Tamoxifen: concurrent use may interfere with each drug’s mechanism and increase adverse event risk.

Moderate Interactions (Monitor Closely)

• CYP2A6 inhibitors (e.g., fluvoxamine): may increase letrozole exposure, requiring observation for toxicity.
• Anticoagulants (e.g., warfarin): letrozole may affect coagulation parameters; monitor INR closely.
• Cholesterol‑lowering agents (e.g., statins): potential for additive musculoskeletal complaints; assess patient tolerance.