All Avandia, all the time. That's how Tuesday and Wednesday of next week will go as GlaxoSmithKline (NYSE: GSK) heads before a marathon two-day Food and Drug Administration advisory panel review of its diabetes drug.

The length of the meeting for a drug that's already on the market tells the story of the complexity of the situation. A retrospective analysis combining multiple studies showed increased heart issues in patients taking Avandia, but one study -- the Record trial -- specifically designed to address the issue showed no increase in heart-related deaths.

It seems the FDA isn't quite sure what to do, so the panel's recommendations may carry more weight than usual. At the end of the meeting, the experts will be asked nine questions including the big one of whether Avandia should get additional warnings on its label, get pulled off the market altogether, or be restricted in use.

While sales have fallen substantially since the initial report of heart issues, Avandia is still a blockbuster, generating more than $1 billion in sales last year; getting pulled off the market would be a big deal for Glaxo. Additional warnings probably won't affect sales too much more because most doctors are probably well aware of the controversy. The meeting isn't likely to end the controversy, however, although it could end Avandia's sales in the United States.

It's not just Glaxo's investors who will be watching the meeting carefully. Takeda's Actos, which is in the same class, will be the big winner if Avandia is pulled from the market. Merck's (NYSE: MRK) Januvia and Onglyza from Bristol-Myers Squibb (NYSE: BMY) and AstraZeneca (NYSE: AZN), which are both oral medication, would likely get some of the patients as well. Injectable drugs such as Amylin Pharmaceuticals (Nasdaq: AMLN) and Eli Lilly's (NYSE: LLY) Byetta and Novo Nordisk's (NYSE: NVO) Victoza could see some increased sales, but certainly not as much as the aforementioned oral drugs.

If Avandia is able to stay on the market, the story isn't over. An ongoing 16,000 patient trial comparing Avandia directly to Actos could seal Avandia's fate one way or the other. That is, if the FDA lets the trial continue.

Stay tuned, Fools! I'll be back here next week with a wrap-up.