A drug has not-so-great side effects, but treats a debilitating disease like epilepsy. In the gray area of risk-benefit analysis, the Food and Drug Administration is likely to take the advice of its outside experts. So when a panel unanimously backed the effectiveness and said the side effects of GlaxoSmithKline (NYSE: GSK) and Valeant Pharmaceuticals' (NYSE: VRX) ezogabine could be managed, the drug seemed like a shoo-in.

Maybe not. There are all those other issues besides the clinical risk-benefit analysis that a drug can get tripped up on. One issue snagged ezogabine; Glaxo and Valeant announced yesterday that the FDA had turned down the drug for now.

Which issue? The duo aren't saying. The abbreviated press release just said that it was for "non-clinical reasons." Glaxo and Valeant plan to respond to the questions "as soon as possible in 2011."

My guess is that REMS is the likely culprit. Ezogabine has some urinary side effects. The FDA likely wants to make sure doctors and patients know the risks and what to look for. The drug also isn't going to be a frontline therapy for epilepsy -- it'll only be used when other drugs aren't working -- so the FDA may want to make sure there's a mechanism in place to ensure doctors are prescribing it correctly.

Fixing a REMS isn't a big deal; Amgen (Nasdaq: AMGN) got its taken care of super quick. Even if it's some other issue -- perhaps manufacturing or maybe some preclinical lab work -- that's still better than having to go back into the clinic. Eli Lilly (NYSE: LLY) and Amylin Pharmaceuticals (Nasdaq: AMLN) got sent back, and it looks like the resulting delay could be more than a year.

It sure would be nice if Glaxo and Valeant had been a little more forthcoming with the reason for the FDA rejection, but investors will just have to accept their word that the drug will be back in front of the FDA soon enough.

Anand Chokkavelu says this "risky" stock isn't that risky.

The Fool owns shares of and has written covered calls on GlaxoSmithKline, which is a Motley Fool Global Gains choice. 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.

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