Tolerability and safety of gastroretentive once-daily gabapentin tablets for the treatment of postherpetic neuralgia

Gordon A Irving,¹ Michael Sweeney<sup>2

1</sup>Swedish Pain and Headache Center, Seattle, WA, USA; ²Depomed, Menlo Park, CA, USA

Objective: An immediate-release formulation of gabapentin is approved for treatment of postherpetic neuralgia (PHN). This formulation, however, requires multiple daily dosing, usually three times per day, and is associated with a high incidence of somnolence and dizziness. We assessed the tolerability and safety of a once-daily gastroretentive formulation of gabapentin (G-GR) in phase 3 clinical trials in patients with PHN.
Research design and methods: Data were pooled from two placebo-controlled studies involving 723 patients (G-GR 1800 mg, n = 359; placebo, n = 364). Patients (43% male, mean age 66 years) with PHN pain >4 (0–10 scale) for ≥3 months were enrolled. Summary statistics for the incidence of treatment-emergent adverse events (AEs) were performed. Laboratory parameters and vital signs were assessed.
Results: Treatment-emergent AEs were reported in 48% of patients (G-GR, 54%; placebo, 42%) and led to discontinuation in 8% of patients (G-GR, 10%; placebo, 7%). The most frequent (≥3% in any group) AEs were dizziness (G-GR, 11%; placebo, 2%), somnolence (G-GR, 5%; placebo, 3%), headache (G-GR, 4%; placebo, 4%), peripheral edema (G-GR, 4%; placebo, ,1%), and diarrhea (G-GR, 3%; placebo, 3%). Serious AEs were reported in seven patients in the G-GR group (2%) and ten patients in the placebo group (3%). There were two deaths, both in the placebo group. No serious AEs were considered related to treatment. Mean values for laboratory parameters and vital signs at the end of each study were similar between groups.
Conclusion: G-GR was safe and well tolerated for the treatment of PHN.

Keywords: gabapentin, postherpetic neuralgia, adverse events, dizziness, somnolence, gastroretentive