Gabapentin for once-daily treatment of post-herpetic neuralgia: a review

Post-herpetic neuralgia is a neuropathic pain syndrome resulting from an insult to the peripheral and central nervous systems caused by the varicella zoster virus. Spontaneous pain may result in the persistent sensation of burning, tingling, or aching and may be associated with thermally or mechanically provoked pain, resulting in hyperalgesia or allodynia. The majority of cases occur in patients over the age of 50 years. Gabapentin is a structural analog of gamma aminobutyric acid that binds to the α(2)-δ site of voltage-dependent calcium channels and modulates the influx of calcium, with a resulting reduction in excitatory neurotransmitter release. Gabapentin is effective in reducing neuropathic pain due to post-herpetic neuralgia when given at least three times per day, due to its short half-life, resulting in demonstrable fluctuations in plasma levels. Gabapentin has dose-limiting side effects that prevent some patients from achieving therapeutic plasma levels, such as somnolence (27.4%), dizziness (23.9%), and ataxia (7.1%). Gralise™ is a once-daily extended-release formulation of gabapentin that has been developed using AcuForm™ technology. AcuForm is a polymer-based drug delivery system that retains the tablet in the stomach and upper gastrointestinal tract for a sustained period of time. Once-daily dosing has been shown to provide comparable drug exposure with an identical daily dose of the immediate-release formulation when administered three times daily. Participants given Gralise 1800 mg daily had a statistically significant reduction in average daily pain intensity scores compared with placebo, reduced sleep interference due to pain, and a greater percent of participants reporting being much or very much improved on the patient global impression of change. An analysis comparing the efficacy and safety profiles in the aging population (≥65 years) with those younger than 65 years showed that Gralise is effective and well tolerated in both age groups.