Vilitra 20 mg you mean vardenafil 20 mg, it can seem to “last for hours” because vardenafil remains active in the body for several hours. Onset: often starts working within about 30–60 minutes. Duration: its effect can commonly remain for around 4–5 hours, although this varies considerably between people. It doesn't mean you should have a continuous erection. The medicine makes it easier to Vilitra 20 mg and maintain an erection when you're sexually stimulated. A higher dose such as 20 mg can increase the likelihood of side effects such as headache, flushing, nasal congestion, dizziness, and low blood pressure. If you have an erection that continues for 4 hours or longer, that's an emergency (priapism) and you should seek immediate medical treatment. Also, don't combine vardenafil with nitrate medicines such as nitroglycerin, and avoid taking more than the prescribed dose.