Here's the problem.  The over the counter products contain exactly the same thing, or a compund so close it's virtually indistinguishable.  The ones that don't have it, don't work. So like any sane person, you're asking, "how can that be?" 

 The companies selling the products have been infringing on Allergan's patent to make a long story short.  The first and largest company to do this was Jan Marini.  Allergan is legally objecting to these patent infringements company by company.  Jan Marini took their similiar product off the market. My understanding is that their new substitute product is not effective.  My guess is that we may see this happening with the other companies as well. 

Dr. Irwin