Efficacy and Tolerability of Gastric-retentive Gabapentin for the Treatment of Postherpetic Neuralgia Results of a Double-blind, Randomized, Placebo-controlled Clinical Trial

Objective: To determine the efficacy and safety of a gastric-retentive, extended-release gabapentin (gabapentin ER) taken once or twice daily for treatment of postherpetic neuralgia. Methods: Using an enrichment design, a randomized, double-blind, placebo-controlled Study was conducted in 158 patients who had experienced pain for at least 3 months after healing of acute herpes zoster skin rash and who had a baseline average daily pain (ADP) score of >= 4 on a 0 to 10 Numerical Rating Scale. Patients received gabapentin ER either once daily (1800 mg PM) or twice daily (600 mg AM, 1200 mg PM) or placebo for 4 weeks. Efficacy measures included changes from baseline to end point in ADP score and average daily sleep interference score. Results: Mean (SI-M) changes for ADP score were - 1.93 (0.28), 2.24 (0.29), and - 1.29 (0.29) in the gabapentin ER once daily, twice daily, and placebo groups. respectively (P = 0.089 and 0.014 for gabapentin ER once daily and twice daily, respectively, vs. placebo), with 25.5%, 28.8%, and 11.8% of patients, respectively, reporting >50% decrease from baseline in ADP score. Mean (SEM) changes in sleep interference scores were - 1.94 (0.30), - 2.28 (0.30), and - 1.16 (0.30), respectively (P = 0.048 and 0.006 for gabapentin ER once daily and twice daily, respectively, vs. placebo). Common adverse events in the gabapentin ER once daily, twice daily. and placebo groups. respectively, were dizziness (22.2%), 11.3%, and 9.8%) and somnolence (9.3%, 7.5%, and 7.8%). Conclusions: Gabapentin ER administered twice daily is effective and safe for the treatment of pain associated with postherpetic neuralgia.