Effect of Moxonidine on the Aldosterone/Renin Ratio in Healthy Male Volunteers.

The most popular screening test for primary aldosteronism is the plasma aldosterone/renin ratio (ARR). Medications, dietary sodium, posture, and time of day all affect renin and aldosterone levels and can result in false-negative or false-positive ARRs if not controlled. Most antihypertensive medications affect the ARR and can interfere with interpretation of results. To our knowledge, no study has been undertaken to evaluate the effects of moxonidine on the ARR. Normotensive, nonmedicated male volunteers (n = 20) underwent measurement (seated, midmorning) of plasma aldosterone (by high-performance liquid chromatography-tandem mass spectrometry), direct renin concentration (DRC), plasma renin activity (PRA), cortisol, electrolytes and creatinine; and urinary aldosterone, cortisol, electrolytes and creatinine at baseline and after 1 week of moxonidine at 0.2 mg/d and a further 5 weeks at 0.4 mg/d. Compared with baseline, despite the expected significant falls in both systolic and diastolic blood pressure, levels of plasma aldosterone [median, 134 (range, 90 to 535) pmol/L], DRC [20 (10 to 37) mU/L], PRA [2.2 (1.0-3.8) ng/mL/h], and ARR using either DRC [8.0 (4.4 to 14.4)] or PRA [73 (36 to 218)] were not significantly changed after either 1 [135 (98-550) pmol/L, 20 (11-35) mU/L, 2.0 (1.2-4.1) ng/mL/h, 8.8 (4.2 to 15.9), and 73 (32-194), respectively] or 6 weeks [130 (90-500) pmol/L, 22 (8 to 40) mU/L, 2.1 (1.0 to 3.2) ng/mL/h, 7.7 (4.3 to 22.4), and 84 (32 to 192), respectively] of moxonidine. There were no changes in any urinary measurements. Moxonidine was associated with no significant change in the ARR and may therefore be a good option for maintaining control of hypertension when screening for primary aldosteronism.