A single 12-week principal efficacy trial and two supportive studies that met their respective primary endpoints evaluated the efficacy and safety of Horizant.
A dosage of 600mg twice daily was recommended for the management of PHN.
Somnolence and dizziness were the most frequently reported side effects in the 12-week, controlled study.
Treatment should begin at a dose of 600mg in the morning for three days followed by 600mg twice daily (1,200mg/day) beginning on day four.
The first commercial sale of the product by GSK after approval triggers a milestone payment of $10m to XenoPort.
Horizant was approved for the treatment of moderate-to-severe primary Restless Legs Syndrome (RLS) in adults in the US on 6 April 2011.