What Protects Medicine Sales, If Not Patents?

The team at NPR's Planet Money took a look at this question for standard headache remedies (asprin, etc) that are long out of patent protection and found that even though cheap generic versions are often shelved side-by-side with the more expensive brand-name versions, brand names still thrive. These are drugs that are long past, or never had, patent protection, so the question of why sales of non-generics still thrive. The answer isn't easy to figure - it has something to do with convenience, something to do with image, and something to do with lack of information. What it does highlight, though, is that monopolistic practices aren't the only route to success in a competitive marketplace.