Similar to Sildenafil, Tadalafil is a PDE5 inhibitor prescribed for the treatment of erectile dysfunction (ED) in men. Tadalafil works by helping to relax the blood vessels in the penis, which can enhance blood flow to improve erectile function. While similar, Tadalafil has some unique differences, including the option to be taken daily at a lower dose regardless of physical activity, it can take longer to become effective, but the effects may last longer than Sildenafil.