Because steroids are lipophilic, they diffuse easily through the cell membranes, and therefore have a very large distribution volume. In their target tissues, steroids are concentrated by an uptake mechanism which relies on their binding to intracellular proteins (or " receptors ", see below). High concentration of steroids are also found in adipose tissue, although this is not a target for hormone action. In the human male, adipose tissue contains aromatase activity, and seems to be the main source of androgen-derived estrogens found in the circulation. But most of the peripheral metabolism occurs in the liver and to some extent in the kidneys, which are the major sites of hormone inactivation and elimination, or catabolism (see below).
Eplerenone is an antimineralocorticoid , or an antagonist of the mineralocorticoid receptor (MR).  Eplerenone is also known chemically as 9,11α-epoxy-7α-methoxycarbonyl-3-oxo-17α-pregn-4-ene-21,17-carbolactone and "was derived from spironolactone by the introduction of a 9α,11α-epoxy bridge and by substitution of the 17α-thoacetyl group of spironolactone with a carbomethoxy group".  The drug controls high blood pressure by binding the aldosterone hormone to the mineralocorticoid receptor (MR) in epithelial tissues, such as the kidney.  This helps to increase blood volume and regulate blood pressure.  It has 10- to 20-fold lower affinity for the MR relative to spironolactone ,  and is less potent in vivo as an antimineralocorticoid.  However, in contrast to spironolactone, eplerenone has little affinity for the androgen , progesterone , and glucocorticoid receptors .   It also has more consistently observed non-genomic antimineralocorticoid effects relative to spironolactone (see membrane mineralocorticoid receptor ).  Eplerenone differs from spironolactone in its extensive metabolism, with a short half-life and inactive metabolites.