Drospirenone is an antagonist of the MR, the biological target of mineralocorticoids like aldosterone, and hence is an antimineralocorticoid. It has about 100 to 500% of the affinity of aldosterone for the MR and about 50 to 230% of the affinity of progesterone for the MR. Drospirenone is about 5.5 to 11 times more potent as an antimineralocorticoid than spironolactone in animals. Accordingly, 3 to 4 mg drospirenone is said to be equivalent to about 20 to 25 mg spironolactone in terms of antimineralocorticoid activity. It has been said that the pharmacological profile of drospirenone more closely resembles that of progesterone than other progestins due to its antimineralocorticoid activity. Drospirenone is the only clinically used progestogen with prominent antimineralocorticoid activity besides progesterone. For comparison to progesterone, a 200 mg dose of oral progesterone is considered to be approximately equivalent in antimineralocorticoid effect to a 25 to 50 mg dose of spironolactone. Both drospirenone and progesterone are actually weak partial agonists of the MR in the absence of mineralocorticoids.
Due to its antimineralocorticoid activity, drospirenone increases natriuresis, decreases water retention and blood pressure, and produces compensatory increases in plasma renin activity as well as circulating levels and urinary excretion of aldosterone. This has been shown to occur at doses of 2 to 4 mg/day. Similar effects occur during the luteal phase of the menstrual cycle due to increased progesterone levels and the resulting antagonism of the MR. Estrogens, particularly ethinylestradiol, activate liver production of angiotensinogen and increase levels of angiotensinogen and angiotensin II, thereby activating the renin–angiotensin–aldosterone system. As a result, they can produce undesirable side effects including increased sodium excretion, water retention, weight gain, and increased blood pressure. Progesterone and drospirenone counteract these undesirable effects via their antimineralocorticoid activity. Accumulating research indicates that antimineralocorticoids like drospirenone and spironolactone may also have positive effects on adipose tissue and metabolic health.