Less adrenergic response to mental task during verapamil compared to amplodipine treatment in hypertensive subjects

Abstract

We compared the effects of amlodipine and verapamil slow release on autonomic responses to a 5-min mental arithmetic test (MST) in patients with mild to moderate hypertension. Twenty subjects received 8 weeks of verapamil slow release 240 mg or amlodipine 10 mg in a double-blind crossover design, both after 4 weeks' placebo. Heart rate (HR) and blood pressure (BP) were continuously monitored. Venous plasma catecholamines were analysed by a radioenzymatic assay. Baroreflex sensitivity (BRS) was estimated with the transfer function technique. Calculations of the area under the curve (AUC) were used to estimate average HR, BP and catecholamine concentrations. The reactivity to MST was estimated as percent change from the basal AUC. A paired t-test was performed. Data are means ±SEM. Compared to verapamil, amlodipine increased average noradrenaline (NA) concentrations (245 ± 23 vs 191 ± 17 pg/l, respectively, p = 0.005), NA reactivity (14.0 ± 5.5% vs -2.9 ± 3.3, p = 0.004), average HR (65 ± 2 vs 61 ± 2 beats/min, p < 0.001) and HR reactivity (2.5 ± 1.0 vs 0.1 ± 0.9%, p = 0.056). BP did not differ significantly. BRS correlated with average and baseline HR on both medications (r = -0.53 and -0.63, p ≤ 0.03). We conclude that adrenergic responses to MST are blunted on treatment with verapamil compared to amlodipine in hypertensive patients.