Alpha-adrenergic blockers vasodilation caused

Alpha-adrenergic blockers are prescribed to treat symptoms of benign prostatic hypertrophy (BPH) and to treat peripheral vascular disease. Alpha-adrenergic blockers also cause vasodilation. 

Phenoxybenzamine is a noncompetitive alpha-adrenergic-receptor blocker, and its action cannot be nuUifled by increasing the amount of agoinst, or agoinsts. It causes epinephrine reversal in that the administration of epinephrine after pretreatment with phenoxybenzamine elicits vasodilation, and, conversely, phenoxybenzamine reverses epinephrine-mediated vasoconstriction to vasodilation (see also Figure 37). 

I. Pharmacology. Phentolamine is a competitive presynaptic and postsynaptic alpha-adrenergic receptor blocker that produces peripheral vasodilation. By acting on both venous and arterial vessels, it decreases total peripheral resistance and venous return. It may also stimulate beta-adrenergic receptors, causing cardiac stimulation. Phentolamine has a rapid onset of action (usually 2 minutes) and short duration of effect (approximately 15-20 minutes). 

ADRENERGIC NEURONE BLOCKERS, ALPHA-BLOCKERS, CENTRALLY ACTING ANTIHYPERTENSIVES, VASODILATOR ANTIHYPERTENSIVES ASPIRIN 1 hypotensive effect not noted with low-dose aspirin Aspirin may cause sodium retention and vasoconstriction at possibly both renal and endothelial sites Monitor BP at least weekly until stable when high-dose aspirin is prescribed... 

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