Alpha adrenoreceptor antagonists prevent the stimulation of alpha-adrenergic receptors at the nerve endings of the sympathetic nervous system. There are two types of alpha-adrenergic receptors, alpha 1 (on the vascular smooth muscle) and alpha 2 (on the vascular smooth muscle and sympathetic nerve terminals).
Alpha-adrenoreceptor antagonists are classed either as non-selective alpha adrenoreceptor antagonists, alpha1-selective antagonists, alpha2-selective antagonists and ergot derivatives.
The medicines used as cardiovascular agents are alpha1-selective antagonists. Alpha1-selective antagonists block the alpha adrenoreceptors on the vascular smooth muscle and widen the arteries, causing vasodilatation and a drop in blood pressure. These agents are used to treat hypertension.
Alpha1-receptor antagonists also cause relaxation of the smooth muscle of the bladder neck and prostate capsule. The longer acting alpha1 antagonists are used to treat urinary retention related to b...