Oral Adjuvant therapy for postmenopausal women with hormone receptor positive early breast cancer, Advanced breast cancer in postmenopausal women, Hormone receptor positive locally advanced breast cancer in postmenopausal women, Hormone receptor positive metastatic breast cancer in postmenopausal women, Hormone receptor unknown locally advanced breast cancer in postmenopausal women, Hormone receptor unknown metastatic breast cancer in postmenopausal women
Adult: 1 mg once daily. Recommended treatment duration: 5 years for adjuvant therapy in postmenopausal women with hormone receptor positive early breast cancer. For the treatment of advanced breast cancer, efficacy has not been demonstrated in estrogen receptor negative patients unless they had a previous positive clinical response to tamoxifen.
Special Patient Group
Pharmacogenomics:
Anastrozole is a selective nonsteroidal aromatase inhibitor. Aromatase enzyme is encoded by CYP19 gene that is responsible for the final step in the conversion of androgen and oestrogens. Oestrogen acts as a growth factor for hormone-dependent breast cancer cells. Genotyping for CYP19 rs4646 gene polymorphism may play an important role in breast cancer survival.
In a study conducted on 406 Chinese women with Stage I-II and operable Stage III breast cancer, the association between CYP19 rs4646 genotypes and disease-free survival (DFS) was evaluated. The study shows that polymorphism is related to DFS in early breast cancer and the prognosis may depend on the menopause status of the patient.
CYP19 rs4646 polymorphism carrier of AA allele
Patient may have increased treatment efficacy in pre-menopausal women and decreased treatment efficacy in postmenopausal women.
CYP19 rs4646 polymorphism carrier of AC or CC allele
Patient may have decreased treatment efficacy in pre-menopausal women and increased treatment efficacy in postmenopausal women.
However, the findings are novel, and if confirmed, rs4646 genotyping may be a potential tool in the management of breast cancer.
Renal Impairment
CrCl (mL/min)
Dosage
<20
Contraindicated.
Administration
May be taken with or without food.
Contraindications
As monotherapy in pre-menopausal women with breast cancer. Severe renal impairment (CrCl <20 mL/min). Pregnancy and lactation.
Special Precautions
Patient with hyperlipidaemia; pre-existing osteopenia, ischaemic cardiac disease. Moderate to severe hepatic or mild to moderate renal impairment.
Adverse Reactions
Significant: Decreased BMD (e.g. osteoporosis), hypercholesterolaemia, hypersensitivity reactions (e.g. anaphylaxis, angioedema, urticaria), ischaemic heart disease. Blood and lymphatic system disorders: Lymphoedema. Cardiac disorders: Angina pectoris, dyspnoea, chest pain. Eye disorders: Cataract. Gastrointestinal disorders: Gastrointestinal distress, anorexia, nausea, vomiting, constipation, diarrhoea, abdominal pain, dyspepsia, gastrointestinal disease, xerostomia. General disorders and administration site conditions: Fatigue, pain, weakness. Injury, poisoning and procedural complications: Bone fracture, accidental injury. Investigations: Weight gain. Metabolism and nutrition disorders: Oedema. Musculoskeletal and connective tissue disorders: Arthritis, myalgia, arthralgia, back pain, ostealgia. Nervous system disorders: Headache, dizziness, paraesthesia, carpal tunnel syndrome. Psychiatric disorders: Mood disorder, depression, insomnia, anxiety. Renal and urinary disorders: UTI. Reproductive system and breast disorders: Pelvic pain, mastalgia, vulvovaginitis, vaginal dryness or bleeding. Respiratory, thoracic and mediastinal disorders: Pharyngitis, cough, flu-like symptoms, sinusitis. Skin and subcutaneous tissue disorders: Rash. Vascular disorders: Vasodilation, hypertension, hot flushes.
This drug may cause asthenia and somnolence, if affected, do not drive or operate machinery.
Monitoring Parameters
Perform pregnancy test prior to initiation of treatment in women with child-bearing potential. Monitor BMD, total cholesterol, LDL, CNS changes, hypotension, thrombophlebitis, bone pain or fracture at regular intervals during therapy.
Drug Interactions
Diminished therapeutic effect with oestrogen derivatives. Decreased serum concentration with tamoxifen.
Food Interaction
Slightly decreases the rate of absorption with food.
Action
Description: Mechanism of Action: Anastrozole, a potent and selective nonsteroidal aromatase inhibitor, inhibits aromatase enzyme by preventing the conversion of androstenedione to oestrone and testosterone to oestradiol, leading to decreased serum estradiol concentration, decreased tumour mass or delayed progression in patients with tumours responsive to hormones. Onset: Estradiol reduction: 70% after 24 hours; 80% after 2 weeks. Duration: Estradiol reduction: 6 days. Pharmacokinetics: Absorption: Rapidly and almost completely absorbed from the gastrointestinal tract. Slightly decreases the rate of absorption with food. Time to peak plasma concentration: Approx 2 hours. Distribution: Plasma protein binding: 40%. Metabolism: Extensively metabolised in the liver via N-dealkylation, hydroxylation and glucuronidation into primary inactive metabolite, triazole. Excretion: Via faeces; urine as metabolites. Elimination half-life: Approx 40-50 hours.
Chemical Structure
Anastrozole Source: National Center for Biotechnology Information. PubChem Database. Anastrozole, CID=2187, https://pubchem.ncbi.nlm.nih.gov/compound/Anastrozole (accessed on Jan. 20, 2020)
Storage
Store between 20-25°C. This is a cytotoxic drug. Follow applicable procedures for receiving, handling, admin, and disposal.
L02BG03 - anastrozole ; Belongs to the class of enzyme inhibitors. Used in treatment of neoplastic diseases.
References
Shao X, Guo Y, Xu X et al. The CYP19 RS4646 Polymorphism IS Related to the Prognosis of Stage I–II and Operable Stage III Breast Cancer. PLoS One. 2015 Mar;10(3). doi: 10.1371/journal.pone.0121535. Accessed 11/11/2019. PMID: 25793413Anon. Anastrozole. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 11/11/2019.Anon. Anastrozole. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 11/11/2019.Arimidex (AstraZeneca). MIMS Hong Kong. http://www.mims.com/hongkong. Accessed 06/11/2020.Arimidex (AstraZeneca). MIMS Singapore. http://www.mims.com/singapore. Accessed 06/11/2020.Arimidex 1 mg Film-Coated Tablets (AstraZeneca UK Limited). MHRA. https://products.mhra.gov.uk/. Accessed 06/11/2020.Arimidex Tablet (Ani Pharmaceuticals, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 06/11/2020.Buckingham R (ed). Anastrozole. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 11/11/2019.Clinical Annotation for rs4646 (CYP19A1); Anastrozole, Cyclophosphamide, Docetaxel, Doxorubicin, Epirubicin, Exemestane, Fluorouracil, Paclitaxel, Radiotherapy or Tamoxifen Breast Neoplasm and Menopause (Level 2B Efficacy). Pharmacogenomics Knowledgebase (PharmGKB). https://www.pharmgkb.org/. Accessed 11/11/2019.Joint Formulary Committee. Anastrozole. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 11/11/2019.The CYP19 Rs4646 Polymorphism is Related to the Prognosis of Stage I-II and Operable Stage III Breast Cancer. Pharmacogenomics Knowledgebase (PharmGKB). https://www.pharmgkb.org/. Accessed 11/11/2019.
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