Approved & therapeutic
Anastrozole
Arimidex
An oral non-steroidal aromatase inhibitor approved in the United States for hormone receptor-positive breast cancer in postmenopausal women. Its use to lower estradiol in men is off-label and not covered by any US indication.
- Status
- Anastrozole is approved by the U.S. FDA and has official prescribing information.
- Evidence
- Approved labeling. Official prescribing information exists, based on clinical trials in people.
- Half-life
- Mean elimination half-life approximately 50 hours, per the US label.
- How it's taken
- Oral.
- Mechanism
- Reproductive axis (GnRH / kisspeptin / oxytocin)
- Pathways
- Estrogen
How Anastrozole works
Anastrozole competitively inhibits the aromatase enzyme, blocking conversion of androgens to estrogens in peripheral tissue. Circulating estradiol falls substantially, which in postmenopausal breast cancer removes estrogenic stimulation of tumour growth and in men removes estrogen negative feedback on the hypothalamic-pituitary axis.
What research has looked at
- Labeled for adjuvant treatment of postmenopausal women with hormone receptor-positive early breast cancer.
- Labeled for first-line treatment of postmenopausal women with hormone receptor-positive or hormone receptor-unknown locally advanced or metastatic breast cancer.
- Labeled for treatment of advanced breast cancer in postmenopausal women with disease progression following tamoxifen therapy; the label notes that patients with ER-negative disease and patients who did not respond to prior tamoxifen rarely responded.
- Lowers circulating estradiol via aromatase inhibition. This is a pharmacodynamic effect, not a demonstrated clinical outcome. It is the stated rationale for off-label use in men during testosterone therapy, but no clinical endpoint in men has been established, and there is no male indication or male regimen on any US label.
- In gynecomastia, the only randomized placebo-controlled efficacy data on the US label are negative: in pubertal boys, anastrozole did not significantly outperform placebo on the primary endpoint of at least a 50 percent reduction in breast volume at 6 months (38.5 percent versus 31.4 percent). The label states efficacy has not been demonstrated in this population.
Evidence level: Approved labeling. Official prescribing information exists, based on clinical trials in people. These are areas studied or reported, not promised effects.
Reported side effects and risks
- Contraindicated in premenopausal women, including any woman who is or may become pregnant: anastrozole may cause fetal harm and offers no clinical benefit in premenopausal breast cancer.
- Contraindicated in any patient who has shown a hypersensitivity reaction to anastrozole or its excipients; anaphylaxis, angioedema and urticaria have been reported.
- Ischemic cardiovascular events occurred more often with anastrozole than with tamoxifen in women with pre-existing ischemic heart disease in the ATAC trial (17 percent versus 10 percent). This finding is specific to that subgroup and should not be generalised beyond it.
- Decreases in bone mineral density, with osteoporosis and fractures reported; bone monitoring is recommended during treatment. The bone and cholesterol warnings derive from trials in postmenopausal women; the same estrogen-lowering mechanism operates in men, where estradiol is also required for bone maintenance, but the magnitude of bone loss in men has not been established in large trials.
- Elevated serum cholesterol, reported more frequently with anastrozole than with tamoxifen.
- May cause fetal harm; effective contraception is advised during treatment and for three weeks after the final dose.
- Common adverse reactions include hot flushes, arthralgia and arthritis, asthenia, pain, bone fracture, osteoporosis, hypertension, depression, insomnia, headache, nausea, vomiting, rash, peripheral edema, lymphedema, pharyngitis and back pain.
- Male use is off-label throughout and there is no labeled dose for men.
Sources
- PubMed research on Anastrozole · NIH · National Library of Medicine
- DrugBank record for Anastrozole · DrugBank
- Active clinical trials for Anastrozole · U.S. National Library of Medicine
Track Anastrozole in Peptide Vault
Log every dose, set reminders on your own schedule, rotate injection sites and keep your vials organized. Peptide Vault records what you enter. It doesn't recommend compounds or doses. iPhone, on-device.
Related compounds
Anastrozole FAQ
What is Anastrozole?
An oral non-steroidal aromatase inhibitor approved in the United States for hormone receptor-positive breast cancer in postmenopausal women. Its use to lower estradiol in men is off-label and not covered by any US indication.
How does Anastrozole work?
Anastrozole competitively inhibits the aromatase enzyme, blocking conversion of androgens to estrogens in peripheral tissue. Circulating estradiol falls substantially, which in postmenopausal breast cancer removes estrogenic stimulation of tumour growth and in men removes estrogen negative feedback on the hypothalamic-pituitary axis.
Is Anastrozole FDA approved?
Yes. Anastrozole is approved by the U.S. FDA and has official prescribing information. Evidence level: approved labeling. Official prescribing information exists, based on clinical trials in people.
What is the half-life of Anastrozole?
Reported half-life: Mean elimination half-life approximately 50 hours, per the US label.
How is Anastrozole taken?
Oral.
What side effects have been reported with Anastrozole?
Reported in the sources: Contraindicated in premenopausal women, including any woman who is or may become pregnant: anastrozole may cause fetal harm and offers no clinical benefit in premenopausal breast cancer; Contraindicated in any patient who has shown a hypersensitivity reaction to anastrozole or its excipients; anaphylaxis, angioedema and urticaria have been reported; Ischemic cardiovascular events occurred more often with anastrozole than with tamoxifen in women with pre-existing ischemic heart disease in the ATAC trial (17 percent versus 10 percent). This finding is specific to that subgroup and should not be generalised beyond it; Decreases in bone mineral density, with osteoporosis and fractures reported; bone monitoring is recommended during treatment. The bone and cholesterol warnings derive from trials in postmenopausal women; the same estrogen-lowering mechanism operates in men, where estradiol is also required for bone maintenance, but the magnitude of bone loss in men has not been established in large trials; Elevated serum cholesterol, reported more frequently with anastrozole than with tamoxifen; May cause fetal harm; effective contraception is advised during treatment and for three weeks after the final dose; Common adverse reactions include hot flushes, arthralgia and arthritis, asthenia, pain, bone fracture, osteoporosis, hypertension, depression, insomnia, headache, nausea, vomiting, rash, peripheral edema, lymphedema, pharyngitis and back pain; Male use is off-label throughout and there is no labeled dose for men.
Educational summary compiled from the sources listed above. Not medical advice. Peptide Vault does not sell, source or recommend any compound. Talk to a qualified clinician before starting or changing anything.