<p>Terazosin is selective for alpha-1-adrenoceptors but not their individual subtypes. Inhibition of these alpha-1-adrenoceptors results in relaxation of smooth muscle in blood vessels and the prostate, lowering blood pressure and improving urinary flow. Smooth muscle cells accounts for roughly 40% of the volume of the prostate and so their relaxation reduces pressure on the urethra.<br />
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It has also been shown that catecholamines induce factors responsible for mitogenesis and alpha-1-adrenergic receptor blockers inhibit this effect. A final long term mechanism of terazosin and other alpha-1-adrenergic receptor blockers is the induction of apoptosis of prostate cells. Treatment with terazosin enhances the expression of transforming growth factor beta-1 (TGF-beta1), which upregulates p27kip1, and the caspase cascade.</p>