Tadalafil is a PDE5 inhibitor that is most commonly used for erectile dysfunction (ED). Tadalafil is the active ingredient in the brand-name medication, Cialis. Tadalafil is in the same class of medications as Viagra (Sildenafil), Levitra (Vardenafil), and Stendra (Avanafil). Tadalafil helps to relax the blood vessels and smooth muscles in the penis to make it easier to achieve and maintain an erection for up to 36 hours.
