Hormonal and Blood Pressure Responses to Tilting in β-Blocked Essential Hypertension Treated with Felodipine or Prazosin
A study was carried out of 22 patients with essential hypertension who were treated with metoprolol (100 mg/day) and placebo for 4 weeks. Felodipine (n = 11) or prazosin (n = 11) were then added in increasing doses (felodipine 5, 10, 20mg bid; prazosin 1, 2, 4mg bid) for 2 weeks until a diastolic blood pressure of ⩽ 90mm Hg was achieved. Acute haemodynamic and hormonal responses to 80° tilting (measurements after 4 minutes’ tilt) were obtained immediately prior to randomisation to felodipine or prazosin, and after 6 to 8 weeks of treatment. At randomisation, 80° tilt produced no change in blood pressure and only a small increase in pulse rate. There was no significant change in the plasma renin-angiotensin system, vasopressin or adrenaline concentrations. Plasma noradrenaline concentration rose in response to 80° tilt. Following substitution of felodipine (n = 11) or prazosin (n = 11) for placebo, and continuation of metoprolol, blood pressure fell. 80° tilt caused no change in the plasma renin-angiotensin sytem, vasopressin or adrenaline concentration. Plasma noradrenaline concentration rose in response to tilt, as before. Felodipine is an effective antihypertensive agent when used with metoprolol. Addition of felodipine to metoprolol did not produce orthostatic hypotension, and was not associated with stimulation of the renin-angiotensin system, or increase in plasma vasopressin concentration. The noradrenergic response to tilt was preserved during felodipine treatment.