Objective: To evaluate the safety and efficacy of a once-daily gastroretentive formulation of gabapentin (G-GR; 1800 mg).
Methods: This was an 11-week, double-blind, randomized, placebo-controlled Phase 3 clinical trial in patients with postherpetic neuralgia. Patients underwent a 2-week dose titration, 8 weeks of stable dosing, and 1 week of dose tapering. The primary endpoint was the change in average daily pain intensity score from Baseline to Week 10 using Baseline Observation Carried Forward (BOCF) imputation.
Results: Four-hundred and fifty-two patients (mean age 65.6 y, BMI 29 Kg/m) were randomized. Baseline average daily pain intensity score during the week prior to randomization was 6.6 and 6.5 for the G-GR and placebo treatment groups, respectively. Three hundred and seventy-seven patients completed the study (84% G-GR, 83% placebo). G-GR significantly reduced BOCF change in average daily pain intensity compared with placebo (-2.1 vs. -1.6; G-GR vs. placebo, P=0.013). Compared with placebo, more G-GR-treated patients reported "much" or "very much" improvement (patient global impression of change, 43% vs. 34%; P<0.0434), and G-GR reduced sleep interference (-2.3 vs. -1.59; P<0.0001), although neither endpoint was considered statistically significant based on a stringent hierarchical statistical paradigm. Other secondary endpoints showed similar trends. The most common adverse events were dizziness (G-GR, 11.3% vs. placebo, 1.7 %) and somnolence (G-GR, 5.4% vs. placebo, 3.0%).
Conclusion: Once-daily G-GR 1800 mg was effective and well tolerated for the relief of pain in patients with postherpetic neuralgia.