Vardenafil (INN) is a PDE5 inhibitor used in the treatment of erectile dysfunction. It can assist men with this disorder in achieving and maintaining an erection during sexual activity. It is commonly marketed under the trade name Levitra (Bayer AG). History Vardenafil was co-marketed by Bayer Pharmaceuticals and GSK under the trade name Levitra. As of 2005, the co-promotion rights of GSK on Levitra have been "transferred back" to Bayer in many markets outside of the United States. In Italy, Ba… (More on Levitra)