Effect of a .BETA.-blocker celiprolol on hemodynamics during exercise loading and the responses caused by sympathomimetic drugs in essential hypertensives.

Celiprolol is a β1 selective β-adrenoreceptor antagonist with intrinsic sympathomimetic activity. The effect of celiprolol on the hemodynamics during exercise loading and the responses caused by adrenergic drugs and the changes of body position were investigated in 9 patients with mild to moderate essential hypertension. Patients were treated with celiprolol 200 mg once a day for 4 to 6 wks, followed by the increased dose of 400 mg for 12 to 14 wks. The hemodynamics during exercise loading were measured in the observation and treatment periods using a bicycle ergometer in the supine position with the constant load of 1.25 W/kg for 6 mins. Blood pressure, heart rate, and cardiac output were measured and the total peripheral resistance was calculated. As sympathomimetic drugs, noradrenaline (NA) and isoproterenol (ISP) were used. Changes of body position were investigated using the electric tilt table.The results were as follows.(1) Celiprolol significantly reduced the increase of blood pressure and heart rate during exercise loading. The increase of cardiac output was not reduced significantly but there was a tendency to decrease. No significant change was found in the total peripheral resistance during exercise loading.(2) The increase of blood pressure caused by NA was not affected by celiprolol but the increase of systolic blood pressure and heart rate caused by ISP was significantly suppressed.(3) Celiprolol did not have an apparent effect on the response of blood pressure and heart rate caused by standing up.Based on the above, celiprolol is considered to suppress the increased blood pressure during exercise loading by reducing the increase of heart rate and cardiac output, and no significant change was found in the total peripheral resistance during exercise loading. On the other hand, as reported before, the hypotensive effect of celiprolol under resting state seems to depend not on the reduction of cardiac output but on mainly the decrease of total peripheral resistance. Therefore, it is suggested that the mechanism of the hypotensive effect of celiprolol from a hemodynamic viewpoint is different during the effort and resting state. The study with sympathomimetic drugs shows that celiprolol has no effect on the vascular α1-adrenergic receptor but significantly blocks the heart β1-adrenergic receptor. Further, celiprolol is considered to have few effects on the baroreceptor reflex according to the result of study with a change of body position.The above study evinces the conclusion that celiprolol is a unique β-adrenoreceptor antagonist which is different from the previously reported drugs. It seems very important for the evaluation of antihypertensive drugs to investigate not only the conventional antihypertensive effect, 24-hr ambulatory blood pressure and hemodynamics during resting state, but also the response to adrenergic drugs, the effect to baroreceptor reflex and hemodynamics during exercise loading.