Gabapentin Enacarbil Significantly Improves Neuropathic Pain Associated with Postherpetic Neuralgia

BALTIMORE, Md.—Up to 3600 mg total daily doses of gabapentin enacarbil, a transported prodrug of gabapentin, significantly improves neuropathic pain associated with postherpetic neuralgia compared with placebo. So found a randomized, double-blind, parallel-group, placebo-controlled study that compared a total daily dose of gabapentin enacarbil 1200 mg, 2400 mg, or 3600 mg with placebo over 12 weeks in adults ≥18 years with postherpetic neuralgia for ≥3 months, a baseline 24-hour average pain score ≥4, and a creatinine clearance ≥60mL/min.

Primary end point was change in baseline to end of treatment in mean 24-hour average pain intensity score, as recorded daily by patients using an 11-point rating scale, where 0 was “no pain” and 10 was “pain as bad as you can imagine,” reported Richard L. Rauck, MD, Carolinas Pain Institute, Winston-Salem, NC, and colleagues. Treatment-emergent adverse events (TEAEs), vital signs, laboratory assessments, and results of electrocardiograms were also recorded.

Of the 376 subjects, 107 were randomized to gabapentin enacarbil 1200 mg; 84 to gabapentin enacarbil 2400 mg, 90 to gabapentin enacarbil 3600 mg, and 95 to placebo. All doses of gabapentin enacarbil significantly reduced 24-hour average pain score: -2.48, -2.28, and -2.80, respectively, vs placebo, -1.67. The adjusted mean treatment difference vs placebo was -0.81 for gabapentin enacarbil 1200 mg (P=0.013); -0.7 for the 2400 mg dose (P=0.029); and -1.07 for the 3600 mg dose (P=0.002).

Dizziness and somnolence were the most commonly reported TEAEs; for the gabapentin enacarbil 1200 mg, 2400 mg, 3600 mg, dizziness occurred in 17%, 26%, and 30% of patients compared with 15% in the placebo group, and somnolence occurred in 10%, 11%, and 14%, respectively, vs 8% receiving placebo.

No clinically relevant changes in vital signs, laboratory assessments, or electrocardiograms were observed, the investigators concluded during The American Pain Society's 29th Annual Scientific Meeting.