These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. Click here for an email preview. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. You’ll soon start receiving the latest Mayo Clinic health information you requested in your inbox. Comparison with actions of other PDE5 inhibitors[ edit ] Sildenafil and vardenafil inhibit PDE6, an enzyme found in the eye, more than tadalafil. Subsequently, the FDA approved both vardenafil [27] and tadalafil in  · US Brand Name Adcirca Cialis Descriptions Tadalafil is used to treat men who have erectile dysfunction (also called sexual impotence). Tadalafil belongs to a . Tadalafil is used to treat male sexual function problems (impotence or erectile dysfunction-ED). In combination with sexual stimulation, tadalafil works by increasing blood flow to the penis to. Cialis is a brand of tadalafil, one of the most popular medications to treat erectile dysfunction (ED).It was first approved in Cialis is popular because it offers dosing flexibility, works.