Does aldosterone-to-renin ratio predict the antihypertensive effect of the aldosterone antagonist spironolactone?

Background: The recognition that some 10% to 15% of the hypertensive population may have aldosterone excess has increased the frequency of measurement of the aldosterone-to-renin ratio (ARR) and the use of aldosterone antagonists. Whether this ratio will predict the blood pressure (BP) response to spironolactone is not clear. Methods: We correlated the BP response to spironolactone 50 mg/day to baseline ARR in 69 hypertensive patients (mean [+/- SD] age 57 +/- 2 years, 65% male), consisting of 39 subjects with long-standing hypertension (4.0 +/- 0.2 years) whose hypertension was uncontrolled on at least three antihypertensive medications and 30 previously untreated patients who were randomized in a crossover design to receive either spironolactone 50 mg/day or bendroflumethiazide 2.5 mg/day for 4 weeks. Results: After 4 weeks of spironolactone, BP in patients with never-treated hypertension was reduced by 18 +/- 3 / 11 +/- 1 mm Hg. There was a highly significant correlation between log ARR and the fall in systolic BP (r = 0.69, P < .001) and diastolic BP (r = 0.45, P < .05). Nine of ten patients with low renin activity (<= 50.5 ng/ mL/h) showed a > 20-mm Hg fall in systolic BP. No such correlations were seen when BP was reduced by bendroflumethazide 2.5 mg. For patients with resistant hypertension, despite a BP reduction of 28 +/- 3 / 13 +/- 2 mm Hg after 14 weeks of spironolactone, there was no relationship between the reduction in BP and the ARR; however, subjects with pretreatment potassium < 4.0 mmol/L had a greater response than those with levels >= 4.0 mmol/L (34 +/- 3 / 16 2 v 20 +/- 6 / 8 3 mm Hg, P < .05) Conclusions: Based on the study results, ARR and low renin activity may predict the response to spironolactone in never-treated hypertensive patients but not in patients taking antihypertensive drugs, possibly because of the effect of these agents on ARR. In such patients a trial of spironolactone is required to assess the BP response.