Fadrozole
A second-generation non-steroidal aromatase inhibitor marketed in Japan (Afema) for breast cancer. It potently lowers estradiol but at higher doses can affect adrenal steroidogenesis, a limitation that later inhibitors overcame.
01 Overview
Fadrozole (Afema) is an imidazole-based non-steroidal aromatase inhibitor approved in Japan for postmenopausal breast cancer. It is considerably more selective than the first-generation aminoglutethimide but less selective than third-generation anastrozole and letrozole.
At higher doses it can inhibit aldosterone and cortisol synthesis, so dosing is kept low. It is not commonly used as a PED ancillary but is discussed among more potent anti-estrogen options.
02 Mechanism
Non-steroidal (type II) reversible aromatase inhibitor: competitively binds the heme iron of aromatase, reducing oestrogen synthesis; partial cross-inhibition of adrenal steroidogenesis at higher doses.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Breast cancer | 1–2 mg/day | Oral | Usually 1 mg twice daily. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Estradiol suppressionReversible aromatase inhibition lowers circulating oestrogen. | Strong estradiol reduction | Clinical | |
| Reduced estrogenic side effectsLower estradiol reduces water retention and gynecomastia risk in androgen users. | Less oestrogenic bloat | Observational |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Adrenal suppressionReduced aldosterone/cortisol synthesis at higher doses. | Moderate | Uncommon (dose-related) | Clinical | |
| Estrogen deficiency symptomsHot flashes, arthralgia and low libido from suppressed estradiol. | Moderate | Common | Clinical |