[Hemodynamic studies on the action kinetics of phenoxybenzamine in healthy persons and hypertensive patients]. / Hämodynamische Untersuchungen zur Wirkungskinetik von Phenoxybenzamin bei gesunden Personen und Patienten mit Hypertonie.

ABSTRACT

The hemodynamic profile of the pre- and postsynaptic alpha-receptor blocker phenoxybenzamine (POB) was investigated by a non-invasive technique in healthy subjects and in patients with essential hypertension. At a dose of 0.03 mg POB/kg body weight no hemodynamic changes were detected. POB at a dose of 0.07 mg/kg resulted in an initial transient rise in systemic vascular resistance and mean arterial pressure and a fall in heart rate without changes in stroke volume or cardiac index. 6 h after administration of 0.13 mg POB/kg a transient fall in peripheral vascular resistance and mean arterial pressure with an increase in heart rate and cardiac index was observed. A rise of orthostatic index, however, occurred within 1 h after administration of POB and reached its maximum after 4 h. 8 h after POB no hemodynamic changes were detectable. In patients with essential hypertension a similar fall in systemic vascular resistance and mean arterial pressure was observed after 0.13 mg POB/kg body weight. No change in heart rate occurred and the hemodynamic effects were significant already 3 h after administration of POB and persisted up to 8 h after POB administration. In contrast to healthy subjects, patients with essential hypertension showed no significant changes in the orthostatic index after POB. These hemodynamic findings point to a previously unexpected rapidly reversible functional alpha-receptor blockade by POB.