About Doxazosin Alpha-1 adrenergic Antagonist, Quinazoline derivative, Antihypertensive. Mechanism of Action of Doxazosin The drug exerts its antihypertensive action by acting as a selective alpha-1 antagonist. It dilates both arteries and veins, thus it reduces total peripheral resistance, reduce blood pressure, & reduce venous return and cardiac output. The alpha-1 blockade in non vascular smooth muscles cause relaxation of smooth muscles of prostate, internal sphincter of the bladder etc. thus decrease the resistance to urinary outflow in patients with benign prostatic hypertrophy. It decrease the tone of prostatic and bladder neck muscles and relaxes bladder trigone, prostate, and prostatic urethra- reduces dynamic obstruction, increases urinary flow rate, causing more complete emptying of bladder. It also induces apoptosis in prostate smooth muscle cells The drug decreases LDL cholesterol & increases HDL cholesterol.