What are cardiovascular effects of phenoxybenzamine?

By blocking α receptors, phenoxybenzamine prevents vasoconstriction of peripheral blood vessels by endogenous catecholamines. the decreased peripheral resistance provokes a reflex tachycardia. the ability to block presynaptic inhibitory α2 receptors can contribute to an increased cardiac output. (Beta1 stimulation) Thus, the drug has been unsuccessful in maintaining lowered blood pressure in hypertension, and it is no longer used for this purpose.