John’s wort. The tablet will quickly dissolve. Oral medicine for ED also might not be safe or work well if you have: Very low blood pressure, called hypotension, or uncontrolled high blood pressure, called hypertension. Ask your doctor if you are not sure if any of your medications contain nitrates. Often, these are prescribed for chest pain called angina. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine. Medicines that block an enzyme called CYP3A4.Vardenafil works best if it’s taken about an hour before sexual activity. You can take vardenafil with or without food, though the medication might work faster if it’s . How long does Viagra take to work? In most people, Viagra works within 1 hour after it’s taken. But in some people, it can begin working as soon as 30 minutes .  · Levitra Staxyn Descriptions Vardenafil is used to treat men with erectile dysfunction (sexual impotence). It belongs to a group of medicines called .