Objective: To determine the effect of gastroretentive gabapentin (G-GR) and describe relationships among pain quality, pain impact, and overall-improvement scores in patients with postherpetic neuralgia (PHN).
Methods: Analyses of integrated data from two Phase 3 studies in which PHN patients received once-daily G-GR 1,800 mg (n = 356) or placebo (n = 363). Neuropathic pain scale (NPS) and brief pain inventory (BPI) were completed at baseline and Week 10; patients' global impression of change (PGIC) at Week 10. Regression analyses described relationships among changes in the NPS, BPI, and PGIC scores.
Results: Compared with placebo, G-GR patients had significant reductions from baseline in individual NPS measures except cold pain (P < 0.05); composite NPS scores (P ≤ 0.003); BPI pain scores (P < 0.05); three individual (mood, sleep, and enjoyment of life) and the average of BPI interference scores (P < 0.05). Clinically significant improvements in BPI interference scores (except walking ability) were positively correlated with reductions in BPI and NPS pain (except dull and cold pain), and with improvements on the PGIC. Reductions in pain qualities at Week 2, especially in NPS pain intensity, were significant (P ≤ 0.0001) predictors of improvements in three BPI interference scores, total NPS score, and PGIC.
Conclusions: For patients with PHN, G-GR provided significant improvements in multiple measures of pain quality and pain-related functional impairment. There was a positive correlation between pain relief and improvement in patient function, with reduction in pain intensity among predictors of improvements in patients' lives. Such comprehensive analyses give an insight into numerous factors that may contribute to better management of PHN.
Keywords: Gabapentin; Gastroretentive; Neuropathic Pain; Pain Intensity; Pain Interference; Pain Quality; Postherpetic Neuralgia; Quality of Life.
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