Earlier quoted context omitted.
What if you allow basically the same ad but disallow mention of any brand names - only the generic name or condition to be treated?
Then we have a tragedy of the commons, where Pfizer and Lilly (the makers of Viagra and Cialis respectively) will wait for the other to create generic ED ads that they will both benefit from.
Also, I imagine that the cost of making and running the commercial would be pretty trivial compared to the profits to be made from the sale of the product.