It looks like the Food and Drug Administration threw the book at Jazz Pharmaceuticals (Nasdaq: JAZZ), but investors seem to think that book is fairly light. The drugmaker is trading up nearly 5% today, even though the FDA declined to approve its fibromyalgia treatment JZP-6.

Of course, investors were clearly expecting Jazz to get sent back to the drawing board; a Motley Poll last week showed rejection beating approval by a 5-to-1 margin. That's not as one-sided as the 20-to-2 recommendation against approval made by the FDA advisory panel, but it was a strong vote of no confidence nonetheless.

What, then, will it take for JZP-6 to gain approval? The answer is less than clear.

Not surprisingly, the agency has a problem with the distribution of the drug. Jazz already sells JZP-6 as a treatment for narcolepsy under the brand name Xyrem, and Jazz will likely have to stick with that name for fibromyalgia. The FDA also wants a new Risk Evaluation and Mitigation Strategies (REMS) to ensure that the drug is only prescribed to patients who should be taking it. Jazz submitted new information after the FDA advisory panel met, but the FDA didn't factor that into the decision.

The bigger concern is the FDA's request for trials to determine safety in patients who are taking additional medications, and to distinguish which patient population should use the product. Given the safety concerns, Jazz may be forced to narrow the population for JZP-6 to patients who have failed all the other options: Pfizer's (NYSE: PFE) Lyrica, Eli Lilly's (NYSE: LLY) Cymbalta, and Savella from Forest Labs (NYSE: FRX) and Cypress Bioscience (Nasdaq: CYPB).

What might the trials look like? That's anyone's guess, including management's. On the conference call today, Bruce Cozadd, Jazz's Chairman and CEO, said, "It is not clear in the letter [from the FDA] what those studies would be, whether they would be small or large, short or long, inexpensive or expensive, pre-approval, post-approval."

Until Jazz figures that out -- presumably in a meeting with the FDA within the next 30 days -- and tells investors, the fate of JZP-6 remains a mystery, and Jazz's shares remain risky.

Interested in keeping track of Jazz as it keeps waits to get more information from the FDA? Add it to My Watchlist, which will help you keep track of all our Foolish analysis on Jazz.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.