GlaxoSmithKline and XenoPort, Inc. announced today that the Food and Drug Administration (FDA) has approved Horizant (gabapentin enacarbil) Extended-Release Tablets for postherpetic neuralgia (PHN) treatment in adults. After three clinical trials involving 574 patients, including a single 12-week principal efficacy study and two supporting trials, the FDA approved Postherpetic Neuralgia treatment....