Aromatase inhibitor (anti-hormonal)
Anastrozole is a medicine used to treat hormone-receptor-positive breast cancer in postmenopausal women. It works by reducing oestrogen production in the body. It is taken orally, one tablet a day.
Also known as: Arimidex
DailyMed/FDA (NIH/NLM) — approved Anastrozole label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=54da5c12-cfaf-7a14-e063-6394a90a3635 ; EMC-UK (MHRA) — approved Anastrozole SmPC: https://www.medicines.org.uk/emc/product/100971/smpc — with additional reference: Prontuário Terapêutico do INFARMED (11th ed., 2012)
Do not take anastrozole and tamoxifen at the same time: there is no added benefit and the combination lowers anastrozole levels in the body.
In the ATAC trial, combining anastrozole with tamoxifen did not improve disease-free survival over anastrozole alone and reduced anastrozole exposure by about 27%. The anastrozole SmPC (EMC-UK) and the approved label state explicitly that it must not be combined with tamoxifen or oestrogen-containing therapies, as these diminish its pharmacological activity.
Co-administration of anastrozole and tamoxifen reduced anastrozole plasma concentration by 27% in the ATAC trial, with no added benefit over monotherapy. Avoid the combination (the ATAC trial showed no advantage).
Competitive effect at the oestrogen receptor and reduced anastrozole exposure.
Treatment response; bone density and lipid profile according to the agent used.
Disease progression; fractures or cardiovascular events on long-term therapy.
Use a single adjuvant hormonal agent (tamoxifen OR aromatase inhibitor), never in combination.
EMC-UK (MHRA) — approved Anastrozole SmPC: https://www.medicines.org.uk/emc/product/100971/smpc ; DailyMed/FDA (NIH/NLM) — approved Tamoxifen label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=509f8ba3-214d-aec8-e063-6294a90af498 ; Prontuário Terapêutico do INFARMED (11th ed., 2012)
Do not use estradiol (or other oestrogens) during anastrozole treatment — oestrogen counteracts the medicine's effect in breast cancer.
Anastrozole acts by inhibiting aromatase, reducing peripheral oestrogen production. Concomitant administration of exogenous oestrogens (hormone replacement therapy, hormonal contraception) replenishes the oestrogen the drug aims to suppress, abolishing or diminishing the antitumour effect. The approved label and the EMC-UK SmPC for anastrozole state that combination with oestrogen-containing therapies should be avoided.
Oestrogen-containing products (including hormone replacement therapy) diminish the activity of anastrozole (aromatase inhibitor). Avoid the combination; HRT is not recommended during adjuvant breast cancer therapy.
Direct pharmacological antagonism: exogenous oestrogen cancels oestrogen suppression.
Signs/symptoms of recurrence; vasomotor symptoms and quality of life.
Vaginal bleeding, new bone pain, breast lump — oncology assessment.
Do not combine oestrogens with anastrozole; discuss non-hormonal options for vasomotor symptoms with the oncologist.
EMC-UK (MHRA) — approved Anastrozole SmPC: https://www.medicines.org.uk/emc/product/100971/smpc ; DailyMed/FDA (NIH/NLM) — approved Estradiol label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5718f042-e8c0-b721-e063-6294a90a5bef ; Prontuário Terapêutico do INFARMED (11th ed., 2012)
Anastrozole can be taken with or without food, with no relevant food interaction.
May be taken with or without food, consistently.
DailyMed/FDA (NIH/NLM) — approved Anastrozole label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=54da5c12-cfaf-7a14-e063-6394a90a3635
Anastrozole is metabolised by CYP3A4; grapefruit may raise its concentrations, although the clinical relevance is unknown.
Avoid grapefruit juice during treatment.
DailyMed/FDA (NIH/NLM) — approved Anastrozole label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=54da5c12-cfaf-7a14-e063-6394a90a3635
Anastrozole lowers circulating oestrogens and can cause a decrease in bone mineral density with an increased risk of fracture.
Assess bone density at baseline and periodically in patients with osteoporosis or high risk; consider bisphosphonates and calcium/vitamin D supplementation according to guidance.
EMC-UK (MHRA) — approved Anastrozole SmPC: https://www.medicines.org.uk/emc/product/100971/smpc
In women with pre-existing ischaemic heart disease, anastrozole was associated with more ischaemic cardiovascular events than tamoxifen.
Weigh risk-benefit in patients with ischaemic heart disease; monitor cardiovascular signs and symptoms.
DailyMed/FDA (NIH/NLM) — approved Anastrozole label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=54da5c12-cfaf-7a14-e063-6394a90a3635
Anastrozole exposure can increase in patients with moderate to severe hepatic impairment; it has not been studied in these populations.
Use with caution in moderate/severe hepatic impairment, with an individual risk-benefit assessment.
EMC-UK (MHRA) — approved Anastrozole SmPC: https://www.medicines.org.uk/emc/product/100971/smpc
Anastrozole is contraindicated in pregnancy; animal studies have shown reproductive toxicity and there are no human data.
Do not administer in any trimester; before starting, rule out pregnancy and use effective contraception.
Contraindicated during breastfeeding due to the lack of data on excretion into milk.
Use effective contraception; anastrozole is not indicated in premenopausal women.
EMC-UK (MHRA) — approved Anastrozole SmPC: https://www.medicines.org.uk/emc/product/100971/smpc
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Aromatase inhibitor used in hormone receptor-positive breast cancer. At 1 mg daily it reduces circulating estradiol by about 70% within 24 hours and by about 80% after 14 days. It does not clinically meaningfully affect corticosteroids, aldosterone or thyroid hormones.
Selectively inhibits the aromatase enzyme (CYP19), reducing the conversion of adrenal androgens (androstenedione, testosterone) into oestrogens (oestrone, oestradiol) in peripheral tissues and in the tumour.
Well absorbed after oral administration, with peak plasma concentrations in about 2 hours. Food does not alter absorption. Plasma protein binding is about 40%.
Extensively metabolised in the liver (about 85% of the dose), by N-dealkylation, hydroxylation and glucuronidation, with involvement of CYP3A4. The metabolites are eliminated mainly in the urine.
The elimination half-life is about 50 hours, with steady state reached after 7 days of daily administration.
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
