Presented at the 2012 AAPM Annual Meeting « Back

Effect of Gabapentin Once Daily on Neuropathic Pain Scale (NPS) Score in Patients with Postherpetic Neuralgia (PHN)

Miroslav Backonja, MD, mishasback@gmail.com¹, Mark S. Wallace, MD², Roy Freeman, MD³, Michael Sweeney, MD⁴, (1) LifeTree Research, Salt Lake City, Utah, (2) University of California, San Diego, La Jolla, California, (3) Beth Israel Deaconess Medical Center N, Boston, Massachusetts, (4) Depomed Inc., Menlo Park, California

Introduction: The Neuropathic Pain Scale (NPS) characterizes pain in 10 dimensions and has been validated in patients with PHN. A once-daily formulation of gabapentin (G-QD) has been developed using extended-release oral gastroretentive delivery technology to overcome the absorption limits of gabapentin. Materials and Methods: The effect of G-QD on pain characteristics was investigated using the NPS scale in two 11-week, double-blind, randomized, placebo-controlled studies. After 1 week of baseline observation, 669 PHN patients (mean age, 66.1 years; 42.6%, male; baseline NPS 10-item average, 5.6) were randomized and titrated over 2 weeks to G-QD 1800 mg or matched placebo (taken with the evening meal), followed by 8 weeks of stable doses. The NPS was administered at baseline and at Week 10. An Institutional Review Board approved both study protocols. Results: Last observation carried forward (LOCF) change in NPS 10-item average score from baseline to Week 10 was -2.5 for G-QD vs. -1.9 for placebo (p = 0.001). Similar changes were seen in non-allodynia items (-2.4 vs. -1.8; p = 0.002) and in the 4 peripheral pain items (-2.6 vs. -1.9; pm = 0.001). G-QD was generally well tolerated; the most common adverse events (AEs) with G-QD were dizziness (10.9% vs. 2.2% for placebo) and somnolence (4.5% vs. 2.7% for placebo). 35 (9.7%) patients in the G-QD 1800 mg group and 25 (6.9%) patients in the placebo group withdrew from the study because of AEs. Conclusions: In patients with PHN, G-QD 1800 mg was well tolerated and improved all dimensions of pain as measured by the NPS.

Funding: Funding for the study was provided by Depomed Inc.