Spironolactone as a nonspecific treatment for primary aldosteronism.

Studies were carried out in 14 patients with primary aldosteronism (1°A) to examine the mechanism(s) by which spironolactone reduces arterial pressure. Measures that produced salt and water depletion were found to consistently reduce arterial pressure. Plasma volume and arterial pressure correlated directly and significantly, r =+0.509 (P <0.001), whether pressure was reduced by spironolactone alone or combined with either hydrochlorothiazide or low dietary sodium, or by rapid sodium depletion alone. With small doses of spironolactone, restricting or liberalizing dietary sodium was associated with decreases or increases, respectively, in arterial pressure and plasma volume. These results suggest 1) that the antihypertensive action of spironolactone is nonspecific and largely dependent on salt and water balance and 2) that maintenance of reduced plasma volume or extracellular fluid volume (ECFV) is a basic component of the pressure response of 1°A to spironolactone therapy.