The cloud of fog sitting over Depomed (Nasdaq: DEPO) is lifting, but we're a ways away from blue skies.

On Friday the drugmaker announced that the Food and Drug Administration had approved Gralise, its treatment for post-herpetic neuralgia (PHN), the pain that occurs after patients get shingles. The news was far from painful for investors; shares are up more than 30% today.

They'd likely be higher if we actually knew who was going to launch the drug and when. Depomed's partner, Abbott Labs (NYSE: ABT), apparently doesn't plan to launch Gralise even though Depomed says it's obligated to do so. The companies are headed into mediation. I'm inclined to think Depomed will end up with the drug and a few bucks in its pocket for its trouble, but the fog won't lift completely until the companies settle their dispute.

Once Gralise is launched, it'll go up against Pfizer's (NYSE: PFE) Lyrica and generic versions of Pfizer's Neurontin. A heavy hitter and a cheap drug are formidable foes, but Gralise looks to have better safety profile and a more convenient dosing regimen. Gralise uses Depomed's extended release technology to allow for once-daily dosing of the active ingredient in Neurontin.

In theory, the biggest threat to Depomed might come from Merck (NYSE: MRK), which sells a shingles vaccine called Zostavax. If most older adults end up getting the vaccine, it could eliminate the potential patients that Gralise treats. No shingles, no PHN, no Gralise sales.

But that's only in theory since Gralise can treat other pain indications as well. The sales force isn't allowed to promote the drug for other indications such as diabetic peripheral neuropathy, a nerve pain disease that diabetics get, but doctors are free to prescribe it off label. I wouldn't expect the off-label prescriptions to happen immediately, but once doctors feel comfortable with using Gralise to treat PHN, they'll likely start prescribing it for other indications. GlaxoSmithKline (NYSE: GSK) and XenoPort's (Nasdaq: XNPT) extended release Neurontin, Horizant, failing to gain FDA approval last year was a big advantage to Gralise since they'd both be competing for off-label sales..

Hopefully investors don't have to take Gralise off-label for protracted partner syndrome, the pain associated with falling stock price because mediation drags on longer than expected.

Pfizer is a Motley Fool Inside Value pick. GlaxoSmithKline is a Motley Fool Global Gains choice. The Fool owns shares of GlaxoSmithKline. Motley Fool Alpha owns shares of Abbott Laboratories. 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., likes making up drugs in his free time. He doesn't own shares of any company mentioned in this article. The Fool's disclosure policy is a hypochondriac.