LETROZOLE — 2.5 mg film‑coated tablets
📦 Product Snapshot
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🧠 Overview
Letrozole is a potent, non‑steroidal, third‑generation aromatase inhibitor. It works by competitively binding to the heme of the cytochrome P450 subunit of the aromatase enzyme (CYP19A1), thereby blocking the conversion of androgens (androstenedione and testosterone) to estrogens (estrone and estradiol). In postmenopausal women, where estrogens are produced primarily via this peripheral pathway, letrozole suppresses circulating estradiol, estrone, and estrone sulfate by 75–95% within 2–3 days.
Oncology (licensed): Letrozole is indicated for adjuvant treatment of hormone receptor‑positive (HR+) early breast cancer in postmenopausal women, extended adjuvant therapy after 5 years of tamoxifen, and first‑line treatment of HR+ advanced or metastatic breast cancer. The BIG 1‑98 trial demonstrated superiority over tamoxifen in disease‑free survival, and it is now a cornerstone of endocrine therapy. It is also used in combination with CDK4/6 inhibitors (ribociclib, palbociclib) for advanced disease.
Reproductive medicine (off‑label, evidence‑based): Letrozole is widely prescribed for ovulation induction in women with polycystic ovary syndrome (PCOS) and unexplained infertility. By temporarily reducing estrogen levels in the early follicular phase, it releases the hypothalamic‑pituitary axis from negative feedback, increasing FSH secretion and promoting follicular development. Studies show higher ovulation rates, lower multiple pregnancy rates (3.4% vs 7.4% with clomiphene), and no adverse endometrial thinning compared to clomiphene citrate.
Key distinctions: Unlike tamoxifen (a SERM), letrozole does not have partial agonist effects on the endometrium. It is highly specific — no clinically relevant effects on adrenal steroidogenesis (cortisol, aldosterone) or thyroid function have been observed. However, it is teratogenic and contraindicated in pregnancy when used for cancer; for fertility use, it is taken early in the cycle and discontinued before conception.
🏷️ Strengths & Brand Examples
- 2.5 mg film‑coated tablets (standard)
- Letroz® 2.5 mg (Sun Pharma)
- Femabene® 2.5 mg (Celon Laboratories) — registered in Philippines as well
- Letripa® 2.5 mg (Cipla)
- Letoval® 2.5 mg (Zydus Cadila)
- Letoripe® 2.5 mg (Naprod Lifesciences) — exported to Philippines
- Femara® (Novartis — US, EU)
- Kisqali Femara® Co‑pack (Novartis — with ribociclib)
⚠️ Safety, Side Effects & Monitoring
- Hot flushes / flashes (>20%)
- Arthralgia / joint pain — often dose‑limiting
- Fatigue, asthenia, dizziness
- Hypercholesterolemia (52% in BIG 1‑98 trial)
- Bone loss / increased fracture risk (monitor BMD)
- Nausea, headache, night sweats
- In fertility cycles: mild ovarian hyperstimulation (rare), multiple pregnancy (3.4% with letrozole vs 7.4% clomiphene)
• Bone effects: Decreased BMD expected. Monitor with DEXA scans; consider bisphosphonates / vitamin D / calcium.
• Lipid monitoring: Check cholesterol at baseline and periodically; 29% of patients in BIG 1‑98 required lipid‑lowering medication.
• Hepatic impairment: In severe cirrhosis (Child‑Pugh C), reduce dose to 2.5 mg every other day (exposure doubled).
• Fatigue/dizziness: Caution driving or operating machinery.
• Hypersensitivity: Rare, but avoid if known allergy to letrozole or excipients.
- Oncology patients: Baseline and periodic bone density scans (every 1‑2 years), lipid profile, liver function tests. Assess for musculoskeletal symptoms.
- Fertility patients (off‑label): Transvaginal ultrasound on day 10‑12 to monitor follicular development and confirm ovulation; avoid intercourse if >2‑3 mature follicles to prevent multiples.
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