HONOLULU, HI—Onset of postherpetic neuralgia (PHN) pain relief with a once-daily gastroretentive formulation of gabapentin can be observed as early as the second day of dosing, reported Mark Jensen, PhD, from University of Washington School of Medicine, Seattle, WA, and colleagues at the American Pain Society’s 31st Annual Scientific Meeting.
The once-daily formulation provides gradual release of gabapentin to the optimal site of absorption in the proximal small intestine and reduces the chance of saturating intestinal uptake. Two 11-week, placebo-controlled PHN studies were conducted to evaluate the time to onset of treatment response. Patients were randomized to receive either 1,800mg of once daily gabapentin (n=357) or placebo (n=364) with their evening meal. Patients underwent a 2-week dose titration to 1,800mg, followed by 8 weeks of stable dosing, and 1 week of dose tapering. Onset of response was defined as the first of two consecutive days with significantly (P<0.05) greater reduction in Numeric Pain Rating Scale (NPRS) scores from baseline in the gabapentin group compared with placebo. Scores were recorded daily in an electronic diary; missing scores were not imputed.
Study results showed significantly greater pain reductions observed for the patients receiving gabapentin group compared with placebo (-6.7% vs. -1.7%, P=0.0043) as early as Day 2, the day after randomization. Pain reductions continued to increase, reaching a maximum at approximately Day 45 (-37.2% vs. -26.2%; P=0.0001), and remained statistically greater in the gabapentin group throughout the 10-week efficacy study period. At Week 10, the mean percent last observation carried forward (LOCF) change in NPRS score was significantly greater with gabapentin than with placebo (−37 vs. −29; P=0.006).
These findings demonstrate that pain reductions after gabapentin treatment can be observed as early as the second day of dosing and continue for at least 10 weeks.