These medications include antifungal, antibiotic and antiviral medications such as ketoconazole, itraconazole, ritonavir, indinavir, saquinavir, atazanavir, and clarithromycin. Many patients are able to have erections without these medications, though often not as easily or frequently. PDE5 Inhibitors. 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. After that, the effects of the Vardenafil will be felt for four to six hours. Only you can make the decision. Therefore, it should not be taken by people taking other medications that affect the QT interval such as amiodarone.What You Need to Know about Vardenafil, the Generic Version of Levitra How it works Dosage Side effects Drug interactions Vs. Levitra, Viagra, Cialis, and Stendra Varendafil cost Summary. Find patient medical information for Levitra oral on MD including its uses, side effects and safety, interactions, pictures, warnings and user ratings. Levitra (vardenafil hydrochloride) is an oral medication taken to treat erectile dysfunction (ED). It’s in the same class of drugs as other popular ED medications, including Viagra and Cialis.