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Indications and Dosage
Oral
Adjuvant therapy for postmenopausal women with hormone receptor positive early breast cancer, Advanced breast cancer in postmenopausal women Adult: In hormone receptor +ve postmenopausal women: 2.5 mg once daily. Treatment may be continued up to 5 yr for extended adjuvant therapy or until tumour progression for advanced breast cancer.
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Hepatic Impairment
Severe (Child-Pugh class C): 2.5 mg every other day.
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Administration
May be taken with or without food.
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Contraindications
Premenopausal status. Pregnancy and lactation.
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Special Precautions
Patient w/ history of osteoporosis and/or fracture. Severe hepatic impairment (Child-Pugh score C) or cirrhosis.
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Adverse Reactions
Significant: Decreased BMD, CNS depression, hypercholesterolaemia.
Nervous: Dizziness, insomnia, somnolence, fatigue, headache, hypertension. CV: Peripheral oedema, HTN, MI. GI: Nausea, anorexia, increased appetite, dyspepsia, constipation, abdominal pain, diarrhoea, vomiting. Resp: Dyspnoea, cough. Hepatic: Increased liver enzymes. Genitourinary: Vag bleeding. Endocrine: Hot flushes, wt gain. Haematologic: Thrombocytopenia. Musculoskeletal: Osteoporosis, bone fracture, arthralgia, myalgia. Dermatologic: Sweating, alopecia; erythematous, psoriaform, maculopapular or vesicular rash, dry skin. |
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Patient Counseling Information
This drug may cause fatigue, somnolence and dizziness, if affected, do not drive or operate machinery.
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Monitoring Parameters
Monitor BP, CBC, thyroid function test, BMD level, serum electrolytes, cholesterol, transaminases, and creatinine periodically.
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Drug Interactions
Tamoxifen, anti-oestrogen agent, oestrogen-containing drugs may diminish the pharmacological action of letrozole. Decreased plasma concentration w/ strong CYP3A4 inducers (e.g. rifampicin).
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Action
Description: Letrozole is a non-steroidal aromatase enzyme inhibitor which competitively binds to the haem of the CYP enzyme, blocking the conversion of androstenedione and testosterone into oestriol and oestradiol respectively, thus, leading to significantly reduced serum oestrogen concentration.
Pharmacokinetics: Absorption: Rapidly and completely absorbed from the GI tract. Distribution: Rapidly and extensively distributed to tissues. Volume of distribution: Approx 1.9 L/kg. Plasma protein binding: Approx 60%, mainly albumin. Metabolism: Metabolised in the liver by CYP3A4 and CYP2A6 enzymes into an inactive carbinol metabolite. Excretion: Mainly via urine (6% as unchanged drug, 75% as glucoronide carbinol metabolite, 9% as unidentified metabolites). Terminal elimination half-life: Approx 2 days. |
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Chemical Structure
 Source: National Center for Biotechnology Information. PubChem Database. Letrozole, CID=3902, https://pubchem.ncbi.nlm.nih.gov/compound/Letrozole (accessed on Jan. 22, 2020) |
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Storage
Store at 25°C. Protect from moisture.
This is a cytotoxic drug. Follow applicable procedures for receiving, handling, admin, and disposal. |
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MIMS Class
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ATC Classification
L02BG04 - letrozole ; Belongs to the class of enzyme inhibitors. Used in treatment of neoplastic diseases.
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References
Anon. Letrozole. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 13/07/2017. Buckingham R (ed). Letrozole. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 13/07/2017. Femara Film-Coated Tablet (Novartis Pharmaceuticals UK Ltd). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 13/07/2017. Joint Formulary Committee. Letrozole. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 13/07/2017. McEvoy GK, Snow EK, Miller J et al (eds). Letrozole. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 13/07/2017.
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