Once-daily gastroretentive gabapentin for the management of postherpetic neuralgia: an update for clinicians.

Gabapentin was originally developed as an add-on anticonvulsant drug, but has been widely used in the USA for the management of postherpetic neuralgia since its approval for this indication in 2002. Gabapentin has a short elimination half life and limited absorption due to a saturable L-amino acid transport system, which is expressed predominantly in the proximal small intestine. Hence, the original immediate-release gabapentin formulation (gabapentin TID) must usually be taken three times a day for optimal efficacy. Gabapentin TID is also associated with a high incidence of dizziness and somnolence and some patients are unable to tolerate the doses required for maximum pain relief. A once-daily, gastroretentive formulation of gabapentin was recently approved by the US Food and Drug Administration (FDA) for the management of postherpetic neuralgia. This formulation provides gradual release of gabapentin to the optimal site of absorption in the proximal small intestine and reduces the chance of saturating intestinal uptake, thus enabling once-daily dosing of gabapentin. This gradual release and absorption have been demonstrated in pharmacokinetic studies in healthy subjects. The efficacy of once-daily gastroretentive gabapentin for the management of postherpetic neuralgia has been demonstrated in placebo-controlled clinical studies. In addition, data from these studies suggest that the incidence of dizziness and somnolence may be reduced compared with similar studies using gabapentin TID. This article provides an overview of the pharmacokinetics, efficacy, and safety of once-daily gastroretentive gabapentin for the management of postherpetic neuralgia.