PDE5 is the enzyme in the body that causes blood vessels to tighten. According to the FDA, generic medications contain the same active ingredients as brand names, meaning there’s no difference in effectiveness or safety. The researchers found that these specific medications help dilate penile arteries and improve blood flow to the penis. These include itraconazole Sporanox, Tolsura , ketoconazole Extina, Ketozole, others and ritonavir Norvir. While each PDE5 inhibitor differs slightly, they’re very similar in treating erectile dysfunction. It should start to work in minutes so long as you are sexually stimulated.Levitra is a member of the impotence agents drug class and is commonly used for Erectile Dysfunction. The cost for Levitra oral tablet 20 mg is around $16 for a supply of 2 tablets, depending on the pharmacy you visit. Vardenafil (Levitra) is almost 10 times more biochemically potent than sildenafil, therefore a lower dose is needed to facilitate the penile erection, potentially resulting in less side effects. Selectivity is the ability of the drug to attach to the specific enzyme PDE 5 found in penile tissues. Vardenafil (Levitra) is more selective than. Extra 15% off $30 sitewide with code SAVE15; Clip your mystery deal! BOGO 50% off select Walgreens health & wellnessMissing: levitra.