Current guidelines recommend withdrawal of treatments that affect the aldosterone/renin ratio (ARR) when screening for primary aldosteronism (PA). However, abandonment of mineralocorticoid-receptor antagonist (MRA) and/or blockers of the renin-angiotensin system can deteriorate control of blood pressure (BP) and hypokalemia. Thus, in consecutive patients with an unambiguous diagnosis of PA in wash-out from confounding treatments and subtyped by AVS, the investigators have compared within-patient the plasma aldosterone and active renin concentration, and the ARR values, measured at baseline, and after a one-month treatment with MRA alone and combined with an AT-1 receptor blocker (ARB). Patients on a regular salt intake have been treated with canrenone (50-100 mg orally) for 1 month, after which olmesartan (10 or 20 mg orally) has been added for another month with up-titration of both treatments over the first 2 weeks to control BP and hypokalemia, however maintaining background therapy. The biochemical variables and the ARR have been assessed in an identical manner at baseline values and after each month of treatment. The investigators calculated that with a sample size of 40 patients the study will have a 95% power to show a clinically significant 20% change in the ARR at an 5% alfa-value using a two-sided paired t-test. Hence, this study will allow to determine if an MRA alone, or added to an ARB at doses that control BP and hypokalemia, affect or not the ARR, thus allow to establish if these agents can be administered or must be forbidden during the screening of PA.
