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. With the approval from the FDA, XenoPort will receive a $10 million milestone payment once GSK has made its first commercial sale of the drug.
According to the press release from GlaxoSmithKline PLC, the recommended dosage for the management of PHN in adults is 600 mg twice daily. Treatment should start with a dose of 600 mg in the morning for three days followed by 600 mg twice daily (1,200 mg/day) beginning on day four.
In the 12-week, controlled study with PHN, somnolence and dizziness as side effects were reported the most. Somnolence was reported in 10 percent of patients treated with 1,200 mg of Horizant per day compared to that of 8 percent of patients receiving a placebo. Dizziness was reported in 17 percent of people receiving 1,200 mg of Horizant per day compared to 15 percent of people receiving placebo.
Postherpetic neuralgia is a nerve pain that lasts for more than a month after a having a shingles infection. Shingles is caused by the varicella zoster virus, the same virus that causes herpes or chickenpox. The pain can last for months or even years. Postherpetic neuralgia occurs mostly in people over age 60. Around one million people in the U.S. get shingles every year and within those million people, 10 percent of them will develop post-herpetic neuralgia.
In April 2011, the U.S. Food and Drug Administration approved Horizant to treat moderate-to-severe restless leg syndrome. It’s not recommended for RLS patients who need to sleep during the day and remain awake at night. Horizant is not approved or licensed outside the US for PHN.
Challenge of Treating PHN
Christopher G. Gharibo, MD, Associate Professor of Anesthesiology, NYU Langone Medical Center, Medical Director of Pain Medicine, NYU Langone’s Hospital for Joint Diseases, New York, NY, discusses the challenge of treating postherpetic neuralgia.