GlaxoSmithKline (NYSE:GSK) has a problem.

Advair turned in over $8 billion in sales last year, accounting for about a quarter of Glaxo's top line.

Advair's composition lost patent protection in 2010, but the patent on part of the Advair Diskus device remains in force until mid 2016. Once that last patent expires, we can probably expect a massive decline in Advair sales. Of course, Glaxo isn't sitting still waiting for a huge portion of its top line to evaporate.

But is it enough?

In the video below, health care analysts Michael Douglass and David Williamson give their take.