Grapefruit and Seville oranges may interact with vardenafil and cause side effects. This medicine also works best when you take it an hour before sex on an empty stomach. Remove an orally disintegrating Staxyn tablet from the package only when you are ready to use the medicine. You can take it in a small dose daily or in a larger dose as needed. Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines. Sildenafil Viagra.Levitra is not a cure for ED and you still need to be aroused for the medication to work. Levitra and its generic version are available in doses of: . Follow the directions on the prescription label. You may take this medication with or without meals. The dose is usually taken 1 hour before sexual activity. You should not . Viagra, Cialis, Levitra, and Stendra are oral medications used to treat erectile dysfunction (ED). You may also know them by their generic names: sildenafil .