Antihypertensive effect of E-643, a new alpha-adrenergic blocking agent

Summary

To determine whether E-643, a new α-blocking agent, would reduce the blood pressure, regardless of the posture, a 1 mg dose was given 3 times daily for 7 consecutive days, to 8 male and 7 female inpatients, aged 37–73 years, with essential hypertension. Blood pressure and pulse rate were measured daily in the supine, sitting and standing positions. Before and after the treatment with E-643, plasma levels of noradrenaline, adrenaline, dopamine-β-hydroxylase, renin and aldosterone were determined, samples being obtained with the subjects recumbent and after standing upright for 60 min. A significant reduction in the systolic and diastolic blood pressures was evident in the supine (172±31/100±12 → 151±28/89±14 mmHg), sitting (158±22/101±11 → 138±28/89±15 mmHg) and standing (153±32/103±21 → 129±31/89±20 mmHg) positions. The reduction in blood pressure remained unchanged throughout the period of administration of E-643. Pulse rate was not affected when the subjects were supine (67±10 → 69±10 beats/min), but was increased in the sitting (68±10 → 73±9 beats/min) and standing (73±10 → 81±11 beats/min) positions. The increased pulse rate tended to decline during continued administration of E-643. Treatment with E-643 produced no significant change in plasma levels of adrenaline, noradrenaline, dopamine-β-hydroxylase, renin and aldosterone. The antihypertensive effect of treatment was more prominent in the patients with higher levels of plasma catecholamines and dopamine-β-hydroxylase, and was less prominent in those with higher plasma renin and aldosterone. Two patients had temporary bouts of dizziness and visual disturbances, but there were no subjective complaints during treatment.