Anastrozole is an aromatase inhibitor. Aromatase inhibitors prevent the conversion of androgens into estrogen in fat, muscle, breast, and brain (1). The medical use of anastrozole is primarily to inhibit the progression and growth of breast cancer in women by blocking the aromatase enzyme. It has also been used by some doctors to try and treat low testosterone production in men, as well as being used in conjunction with testosterone replacement therapy.
For bodybuilders and strength athletes, anastrozole is used to minimize the aromatization of anabolic steroids, and to a lesser extent for it’s ability to raise testosterone levels in users. By reducing the amount of estrogen in a steroid user’s body he will be able to avoid estrogen related side effects such as water retention, gynocomastia, etc (2). Obviously this is something that users should be hoping to limit as much as possible.
Interestingly, in addition to decreasing estrogen it has been demonstrated that anastrozole can also increase testosterone levels by up to 58%, along with also raising levels of lutenizing hormone (3). This is quite significant especially when one considers that anastrozole can be used in conjunction with other compounds during a user’s post cycle therapy to raise natural testosterone levels once administration of anabolics steroids is completed via the hypothalamic testicular pituitary axis.
In the majority of users, .5mgs per day should be enough to prevent any estrogen related side effects related to anabolic steroid use. Even when doses were increased to 1 mg per day there was no change in the amount of estrogen that was able to be reduced as compared to doses of .5mgs per day (3). This would seem to indicate that raising your dosage will show no further results if estrogenic side effects continue to be a problem at a dosage of .5mgs. If symptoms persist the user may have to try a more potent compound such as femara (4).
Having said all of this however, most users will be able to reduce any water retention that they may have, or other estrogen related side effects, with dose less than .5mgs per day. Anecdotally users have reported that doses in the range of .25mgs per day or .5mgs every other day are enough to acheive this result. It is possible to administer anastrozole every other day due to it’s active life of 48 hours.
For users using anastrozole during their post cycle therapy the same dosages should apply. There is no need to increase or decrease dosages. It can be run throughout the post cycle period with no ill effects.
Blood levels of the compound should stabilize and reach their peak at about 7-10 days after first administering the drug (5). Therefore it is unlikely that a user would need to frontload with anastrozole or begin taking it before they start administering the anabolics that they plan on taking.
Anastrozole is seemingly very mild on blood lipids (cholesterol) and has not been shown to affect them adversely (6,7). However it should be noted that in theory if one was to consistently suppress your natural estrogen levels for a long period of time, this would negatively impact your health (including your cholesterol). Despite this there is no scientific evidence that anastrozole can be dangerous for healthy individuals to use, even for extended periods of time.
It would seem then that anastrozole has little in the way of negative side effects associated with it’s use. It is by far one of the safest compounds that an athlete can use.