GlaxoSmithKline's drug Horizant has been approved by the Federal Drug Administration for treatment of nerve pain caused by shingles.

GSK and its partner XenoPort announced Thursday that Horizant has been approved for the treatment of adults suffering from a nerve pain syndrome called postherpetic neuralgia, or PHN.

Some shingles patients suffer from PHN after recovering from an outbreak of the disease. The syndrome can cause pain in the area where shingles occurred for months or even years afterward.

About 10 percent of the 1 million people who develop shingles in the U.S. each year develop PHN.

Horizant is also approved for the treatment of Restless Leg Syndrome in adults.

California-based XenoPort is entitled to a $10 million milestone payment from GSK after the first commercial sale of the drug.

GSK has about 3,800 workers at its North American headquarters in Research Triangle Park and 600 at its manufacturing plant in Zebulon.