English: Androgen receptor antagonistic potency of spironolactone, cyproterone acetate, and flutamide in male rats. Measured as dose-dependent reduction of ventral prostate weight (mg) in castrated male rats treated with 0.2 mg/kg/day testosterone propionate (Hershberger assay). The weight of the ventral prostate is stimulated by and dependent on androgens. Cyproterone acetate and flutamide had similar potency in this assay whereas the potency of spironolactone was substantially lower.

In this study, the relative binding affinities (RBAs) of the androgen receptor antagonists for the human androgen receptor were also determined. The RBAs compared to dihydrotestosterone (100%) were 2.70% for spironolactone and 11.5% for cyproterone acetate, whereas the RBA of flutamide (or of its active metabolite 2-hydroxyflutamide) was not reported.

Source of the data:

• (February 2004). "Comparison of the Hershberger assay and androgen receptor binding assay of twelve chemicals". Toxicology 195 (2-3): 177–86. DOI:10.1016/j.tox.2003.09.012. PMID 14751673.