OBJECTIVES: The aldosterone-to-renin ratio (ARR) is frequently used for screening primary hyperaldosteronism. This study aims to assess the influence of antihypertensive drugs, body posture, demographic factors and circadian rhythms on this ratio.

DESIGN AND METHODS: In a prospective, randomized, open-label, parallel-designed protocol preceded by a 4-week placebo run-in period;
57 essential hypertensives (41 men, 16 women) were randomized to a morning dose (9h00) of telmisartan 80 mg (T80), ramipril 10 mg (R10) or amlodipine 10 mg (A10) for 8 weeks. Morning standing (10 minutes) and 24-hour supine blood pressure (BP), plasma renin (pg/ml), plasma aldosterone (pg/ml) and plasma catecholamines (pg/ml) concentrations were assessed at baseline and after 8 weeks of therapy.

RESULTS: There was no relation between ARR and demographic factors or BP. Under placebo, supine ARR exhibited statistically and clinically significant circadian variations with the lowest and peak values averaging 20.1±11.6 and 57.8±30.5 respectively. Mode time to lowest and highest values was 24h00 and 8h00 respectively. T80, R10, and A10 decreased ARR significantly at almost all 24h time points as illustrated by a decrease from 44.1±21.4, 47.8±20.3 and 49.7±32.0 to14.6±9.6, 34.1±22.3 and 33.1±24.2 respectively 24h post dose. T80 decreased ARR significantly more than R10 and A10 because it induced greater decrease in plasma aldosterone and greater increase in plasma renin. Under placebo, morning ARR tended to increase from 47.3±25.4 when supine to 54.5±43.9 when standing (p=0.17).

CONCLUSIONS: The ARR is significantly influenced by circadian rhythms, T80, R10 and A10 but not posture in patients with essential hypertension. T80 decreased the ARR significantly more than A10 and R10. Administration and interpretation of the ARR should take these influences into account.

DNC

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