1. The calcium slow channel inhibitor verapamil was administered as monotherapy (240-270 mg; mean 427 mg/day) on the average for 93 days to 43 patients with essential hypertension; 11 with low, 24 with normal and eight with high renin sodium index.

2. Verapamil reduced blood pressure from 171 ± 16/108 ± sd 6 mmHg to 152 ± 14/93 ± 9 (both P < 0.001); in 25 of the 43 patients a diastolic pressure ≤95 mmHg was achieved. Two patients each reported vertigo, sleeplessness and constipation.

3. The fall in mean blood pressure after verapamil was directly related to age (r = 0.759, P < 0.001), pretreatment mean blood pressure (r = 0.701, P < 0.01) and plasma noradrenaline concentration (r = 0.400, P < 0.05), and inversely related to plasma renin activity (r = −0.551), P < 0.001). These correlations were also significant for diastolic blood pressure. Accordingly, the antihypertensive response to verapamil was greatest in older and low renin patients.

4. This greater blood pressure decrease with verapamil in older and low renin patients suggests a greater calcium influx-dependent vasoconstriction in these patients, which seems to be directly related to the activity of the sympathetic nervous system.

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