LAS VEGAS, NV — A once-daily gastroretentive formulation of gabapentin, which for patients in the fed state lingers in the stomach for an estimated 8 hours, can be an efficacious option for postherpetic neuralgia, including a very elderly (age ≥75 years) population, as presented at PAINWeek 2012.

When dosed three times daily, gabapentin is linked to adverse effects of somnolence and dizziness; these unfavorable consequences may prevent the achievement of optimal therapeutic dosages and are especially worrisome for older individuals, who are prone to falls. A once-daily formulation, also approved for postherpetic neuralgia, minimizes the aforementioned adverse effects and permits patients to achieve their best possible dose.

Wendy Smith, MD, from Depomed, and colleagues conducted integrated efficacy analyses on two placebo-controlled, Phase 3 studies of patients >75 years with postherpetic neuralgia. This included 333 patients who received 1,800mg of gastroretentive gabapentin and 340 patients who received placebo, both of which were taken with the evening meal.

Primary efficacy included change in average daily pain as measured by the Numeric Pain Rating Scale (NPRS), with scores noted every morning from Baseline to Week 10. Secondary efficacy assessments consisted of the percentage of responders, Patient Global Impression of Change at Week 10, and change from Baseline to Week 10 in average daily sleep interference score. Subgroup analyses were conducted based on age (≥75 years [100 in the active group and 92 in the placebo group] and <75 years).

The mean absolute change in the numeric pain rating scale score was significantly greater with gastroretentive gabapentin than with placebo (-2.3 vs. -1.5; P=0.0025). Additionally, a greater number of gastroretentive gabapentin patients achieved a ≥30% reduction vs. placebo (53% vs. 30%; P=0.0025).

For the Patient Global Impression of Change at Week 10, significantly more patients in the gastroretentive gabapentin group felt “Very Much” or “Much” improved compared with patients in the placebo group (P=0.001). The change in Sleep Interference Score (SIS) was also significantly greater for patients who were treated with gastroretentive gabapentin than for patients receiving placebo (-2.4% vs. -1.3%; P<0.0017).

There were no significant increases in the frequency of adverse events for patients aged ≥75 years vs. all patients. For patients aged ≥75 years, serious adverse events took place in 0.8% of patients in each group.

The investigators concluded that as gastroretentive gabapentin had similar safety and efficacy profiles in patients aged ≥75 years as compared to the overall population, it can be a viable therapeutic option for postherpetic neuralgia in this subgroup.