<p><strong>Use with phosphodiesterase-5 inhibitors (PDE-5 Inhibitors)</strong>: Concomitant useo f PDE-5 inhibitors (e.g. Sildenafil, Tadalafil, Vardenafil) and Prazosin may lead to symptomatic hypotension in some patients. Adding Prazosin to beta-adrenergic antagonist or calcium antagonist therapy may produce a substantial reduction in blood pressure.</p>