Shares in DepoMed, a small pharmaceutical enhancer, spiked Monday after the company announced that the FDA had approved the use of its drug Gralise, an oral treatment for postherpetic neuralgia, a complication of shingles that causes sustained pain in nerve fibers and skin.

FORBES: Drug Approval Boosts Cheap Pharma Stock

Instead, doctors found that Neurontin helped with many other ailments, particularly pain caused by nerve damage due to conditions like shingles and diabetes. (This is called neuropathic pain.) That put Warner-Lambert in a bind, because it could not promote the drug for these unapproved uses.

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But if the pain lasts long after the shingles rash and blisters have disappeared, it's called postherpetic neuralgia.

CNN: Postherpetic neuralgia

Lyrica was finally approved on the last day of 2004--but solely as a treatment for pain due to nerve damage from shingles or diabetes and as a controlled substance.

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In a trial of 38, 546 people 60 and up, sponsored by the VA and Merck, a single dose reduced the incidence of shingles over the next three years by half and slashed severe cases of postshingles pain (usually lasting three months or more) by two-thirds, according to the results in the New England Journal of Medicine (June 2, 2005).

FORBES: Magazine Article