Safety and Efficacy of Once-Daily Gastroretentive Gabapentin in Patients with Postherpetic Neuralgia Aged 75 Years and Over

BACKGROUND: Treatment of postherpetic neuralgia (PHN) is more complicated in elderly patients, and multiple daily dosing, complex titration, and high incidences of adverse events can be limiting for many pharmacological treatment options. OBJECTIVE: The aim of this study was to determine whether the efficacy and tolerability of once-daily gastroretentive gabapentin (G-GR) is similar between elderly patients (≥75 years) and younger patients (<75 years). METHODS: Data from two phase III, placebo-controlled studies of 1,800 mg G-GR once daily with dinner in patients with PHN were integrated and analyzed by age subgroups (<75 years, n = 527; ≥75 years, n = 192). Efficacy assessments at endpoint (week 10) included baseline-adjusted change in average daily pain (ADP) and average daily sleep interference (SIS) scores, the proportion of responders (≥30 % pain reduction), and the proportion of patients feeling “Much” or “Very Much” improved on the Patient Global Impression of Change (PGIC). RESULTS: Compared with placebo, patients in both age subgroups treated with G-GR (placebo/G-GR) had greater reductions in mean ADP (≥75: −21.9/−34.2 %, p = 0.0348; <75: −29.9/−38.3 %, p = 0.0079) and SIS (≥75: −1.3/−2.4, p = 0.0017; <75: −1.8/−2.7, p < 0.0001), more patients were responders (≥75: 30.4/52.0 %, p = 0.0025; <75: 45.0/54.7 %, p = 0.0265), and more felt “Much” or “Very Much” improved on the PGIC (≥75: 20.7/35.0 %, p = 0.0272; <75: 33.6/44.9 %, p = 0.0077). The most common (placebo/G-GR) adverse events (AEs) were dizziness (≥75: 3.3/12.0 %; <75: 1.8/10.4 %), nausea (≥75: 1.0/5.4 %; <75: 2.9/4.2 %), and somnolence (≥75: 0/5.0 %; <75: 3.7/4.2 %). For all patients, AEs rapidly decreased to low steady levels after 4–5 weeks of treatment. The incidence of serious AEs was low and they were reported more frequently in the placebo than in the G-GR group. CONCLUSIONS: Therapy with once-daily G-GR was as effective for treating pain associated with PHN in elderly patients as it was in younger patients. G-GR was well tolerated, and the incidence of the most common AEs did not appear to be age related.