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.

Leaked: This coming blockbuster will make every biotech jealous
The best biotech investors consistently reap gigantic profits by recognizing true potential earlier and more accurately than anyone else. Let me cut right to the chase. There is a product in development that will revolutionize not how we treat a common chronic illness, but potentially the entire health industry. Analysts are already licking their chops at the sales potential. In order to outsmart Wall Street and realize multi-bagger returns you will need The Motley Fool's new free report on the dream-team responsible for this game-changing blockbuster. CLICK HERE NOW.

David Williamson owns shares of Novartis. Michael Douglass has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.