Spironolactone is a strong AR antagonist (IC50 ~ 77 nM), a weak GR antagonist (IC50 ~ 2.4 μM), and a weak PR agonist (EC50 ~ 740 nM). [1] Spironolactone inhibits androstanolone binding in rat prostate nuclei and androstanolone specific binding in rat prostate cytosol. [2]