Question: what is the difference between viagra and vardenafil?
Answer: Sildenafil (Viagra) has a half-life of 4 hours and vardenafil (Levitra) has a half-life of 4-6 hours while tadalafil (Cialis) has a half-life of 17.5 hours. This means that vardenafil (Levitra) should act longer than sildenafil (Viagra) but the clinical significance is not known.