This medication usually starts working within 30 to 60 minutes after ingestion and can last up to 4 or 5 hours. It is important to follow the prescribed dosage. Vilitra 20 mg, which contains vardenafil, works by inhibiting the action of an enzyme called PDE5, increasing the levels of a chemical called nitric oxide. This process relaxes the blood vessels in the p*nis, increasing blood flow during s*xual stimulation.