Long-term safety of gastroretentive gabapentin in postherpetic neuralgia patients.

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.