The action mechanism of Minipress XL in causing hypotension is unknown. However, it has been found that the drug reduces total peripheral resistance. The drug was originally believed to have a direct action vascular smooth muscle, but it studies have suggested that prazosin has a vasodilator effect by blocking postsynaptic alpha-adrenoceptors, which is why it is called an alpha-blocker. Postsynaptic alpha-adrenoceptors have vasoconstriction-like effects. By lowering blood pressure, Minipress XL helps the blood to flow freely across the body.