I Purchase Viagra 100mg Tablets At $50+ Per Tablet. I

I purchase Viagra 100mg tablets at $50+ per tablet. I want to switch to "Revatio" or "Sildenafil 20mg" because of the cost. Are Revatio and Sildenafil 20mg just different names for the same product? I now cut the 100mg Viagra tablets into quarters. I would want to take the Rev or Sil 20mg tablets as needed (up to 520mg = 100mg) at one time. I am asking you this question as a second opinion. I will be discussing this with my cardiologist whom I will see in the next week.