Anastrozole is a nonsteroidal aromatase inhibitor: it blocks aromatase, the enzyme that converts testosterone into estradiol. It is sold as Arimidex and as generic tablets.
Also known as: Arimidex.
Arimidex and generic anastrozole come as 1 mg tablets, the only strength on the FDA label.
The FDA label approves anastrozole only for postmenopausal women with breast cancer: adjuvant treatment of hormone receptor-positive early breast cancer, first-line treatment of hormone receptor-positive or unknown advanced breast cancer, and advanced breast cancer that progressed after tamoxifen. The labeled dose is 1 mg once daily, with or without food. There is no approved use in men, and a placebo-controlled study in the label found no benefit for gynecomastia in pubertal boys.
On TRT, anastrozole is used off-label to lower estradiol. The American Urological Association 2018 guideline says clinicians may use aromatase inhibitors, hCG, SERMs or a combination in men with testosterone deficiency who want to maintain fertility (a conditional recommendation), and notes that only hCG is FDA approved for use in males. Whether to take it, and how much, is a decision for you and your prescriber. When it might be warranted, and how to test estradiol first, is covered in Estradiol (E2) on TRT. For fertility-preserving options, see hCG vs enclomiphene.
The FDA Arimidex label gives a mean elimination half-life of 50 hours; Dose Track uses 48 hours. Peak levels typically occur within 2 hours of a dose on an empty stomach (about 5 hours if taken after a meal, with the same total absorption), and steady state is reached after about 7 days of once-daily dosing.
Numbers shown are the values Dose Track uses, listed only where they agree with the source above. Half-life varies from person to person and with injection site.