P-593: Drug effects on aldosterone/plasma renin activity ratio in primary aldosteronism

We investigated the effect of atenolol, amlodipine, doxazosin, fosinopril, and irbesartan on the aldosterone/plasma renin activity ratio (ARR). ARR is routinely used as a screening test for primary aldosteronism, a common and specifically treatable form of secondary hypertension. Antihypertensive drugs can interfere with the interpretation of ARR, but a correct washout period can be potentially harmful. We measured ARR during single-drug therapy and after a 1-month washout period in a group of 230 patients with hypertension referred to our unit. The percent change of ARR in patients taking amlodipine was -17%±32; atenolol, 62%±82; doxazosin, -5%±26; fosinopril, -30%±24; and irbesartan, -43%±27. The ARR change induced by atenolol was significantly higher compared with that induced by all other drugs (P