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Long-term Safety of Gastroretentive Gabapentin in Postherpetic Neuralgia Patients

Jensen, Mark P. PhD*; Irving, Gordon MD; Rauck, Richard MD; Wallace, Mark MD§; Sweeney, Mike MD; Vanhove, Geertrui F. MD, PhD∥,¶

doi: 10.1097/AJP.0b013e31827b32ab
Original Articles

Objective: This study evaluated the long-term safety and tolerability of a gastroretentive formulation of gabapentin (G-GR) and its effect on weight gain in postherpetic neuralgia (PHN) patients participating in a 14-week, open-label extension to a 10-week double-blind study.

Methods: Patients with PHN≥3 months, who had completed participation in a phase 3 randomized, double-blind, placebo-controlled study of the safety and efficacy of G-GR in PHN, who wished to continue treatment with G-GR, and who the investigator thought would benefit from study participation received G-GR 1800 mg as an asymmetrically divided dose (600 mg AM/1200 mg PM) for an additional 14 weeks. Analyses were performed on safety data from patients who received G-GR for 10 weeks in the randomized controlled study and who then received an additional 14 weeks of G-GR, asymmetrically dosed in the current study. Safety assessments included the incidence and severity of adverse events (AEs), the occurrence of serious AEs, changes in physical and neurological examination findings, clinical laboratory assessments, and changes in weight.

Results: Eighty patients treated with G-GR in the randomized, controlled study participated in this 14-week extension study. The incidence of AEs commonly observed with gabapentin (dizziness, somnolence) was low and the frequency, intensity, and severity of AEs did not change with long-term treatment. The mean weight change from baseline in the randomized controlled study to the end of the extension study was +0.76 kg. Weight increase was reported as an AE for 2 (2.5%) patients.

Conclusions: Long-term treatment (up to 24 wk) with G-GR of 1800 mg was well tolerated and associated with little weight gain (<1 kg) in patients with PHN. No new safety issues emerged with G-GR long-term treatment.

*Department of Rehabilitation Medicine, Harborview Medical Center, University of Washington School of Medicine

Swedish Pain and Headache Center, Seattle, WA

Center for Clinical Research, Winston-Salem, NC

§University of California, San Diego, San Diego School of Medicine, La Jolla

Depomed Inc., Menlo Park

Now at Jazz Pharmaceuticals, Palo Alto, CA

All authors are responsible for the work described in this paper, and they contributed to the conception, data interpretation, and drafting of the manuscript and/or revising the manuscript for important intellectual content. All authors provided final approval of the version to be published.

Source of Funding: The analyses for this study were supported by Depomed Inc., Menlo Park, CA.

Potential conflicts of interest: M.P.J. has received grant/research support from and has served as a consultant to Depomed, and has received consulting fees or research support from Pfizer, Salt Lake City, UT, ZARs Pharma, Salt Lake City, UT, Merck, Whitehouse Station, NJ, RTI Health Solutions, Triangle Park, NC, Covidien, Mansfield, MA, Bristol-Myers Squibb, New Brunswick, NJ, Endo, Chadds Ford, PA, Schwarz Biosciences, Raleigh, NC, and Smith & Nephew, London, UK within the past 36 months. G.I. has received compensation for serving on the advisory board and the speakers bureau for Depomed. He has also served on the advisory board for Eli Lilly, Indianapolis, IN, Endo, Chadds Ford, PA, Neurogesx, San Mateo, CA, and Zogenix, San Diego, CA. R.R. and M.W. were investigators in the Depomed studies and also serve as consultants to Depomed. R.R. is a speaker for Depomed. M.S. is a Depomed employee, owns Depomed stock and holds Depomed stock options. G.F.V. was a Depomed employee when the analyses for this paper were designed and completed, and the original submission was written. Stella Chao, who provided assistance in editing the manuscript has worked as a consultant for Depomed.

Reprints: Mark P. Jensen, PhD, Department of Rehabilitation Medicine, Harborview Medical Center, University of Washington, Box 359612, 325 Ninth Avenue, Seattle, WA 98104 (e-mail: mjensen@uw.edu).

Received March 19, 2012

Accepted October 25, 2012

© 2013 by Lippincott Williams & Wilkins