Effect of verapamil sustained-release on the sympathetic nervous system response to isometric stress in patients with essential hypertension: A pilotstudy in Turkish patients

Background: Stress and sympathetic nervous system activation play a major r ole in the pathogenesis of essential hypertension. Recent data suggest that the calcium channel blocker verapamil, in addition to its antihypertensive effects, can alter the level of norepinephrine released during stress. Objective: The purpose of this study was to examine the effects of verapami l sustained-release (SR) on the sympathetic nervous system response to stre ss in patients with essential hypertension. Methods: Patients with essential hypertension (diastolic blood pressure >90 mm Hg and systolic blood pressure >140 mm Hg) whose blood pressure was ina dequately controlled or uncontrolled were enrolled in the study. Secondary hypertension was ruled out by routine biochemical, endocrine, and radiologi c tests. After a 15-day washout period during which all previous antihypert ensive medication was discontinued, blood pressure, heart rate, and serum n orepinephrine levels were measured at rest and in response to stress (ie, i sometric exercise). Patients began treatment with verapamil SR at dosages r ecommended in the Sixth Report of the Joint National Committee for the Prev ention, Diagnosis, Evaluation, and Treatment of High Blood Pressure (240 mg /d for stage I hypertension and 480 mg/d for stage II and stage III hyperte nsion). After 4 weeks of treatment, blood pressure, heart rate, and norepin ephrine levels were measured again at rest and in response to stress. Results: Thirteen patients (9 women and 4 men) were enrolled; 9 patients co mpleted the study. Three patients were lost to follow-up and 1 was noncompl iant. Verapamil SR significantly lowered norepinephrine levels both at rest and in response to stress (P<0.01), and reduced the increase in norepineph rine levels after isometric exercise. Conclusion: These results suggest that in this small sample of Turkish pati ents, verapamil SR significantly diminished the sympathetic nervous system response to stress by decreasing norepinephrine levels. This property may m ake verapamil SR especially useful when there is a need for decreased sympa thetic activity (and thereby, a reduction in oxygen consumption) as well as other antihypertensive effects, such as in patients with coronary heart di sease.