Development and Evaluation of Topical Gabapentin Formulations

Topical delivery of gabapentin is desirable to treat peripheral neuropathic pain conditions whilst avoiding systemic side effects. To date, reports of topical gabapentin delivery in vitro have been variable and dependent on the skin model employed, primarily involving rodent and porcine models. In this study a variety of topical gabapentin formulations were investigated, including Carbopol^® hydrogels containing various permeation enhancers, and a range of proprietary bases including a compounded Lipoderm^® formulation; furthermore microneedle facilitated delivery was used as a positive control. Critically, permeation of gabapentin across a human epidermal membrane in vitro was assessed using Franz-type diffusion cells. Subsequently this data was contextualised within the wider scope of the literature. Although reports of topical gabapentin delivery have been shown to vary, largely dependent upon the skin model used, this study demonstrated that 6% (w/w) gabapentin 0.75% (w/w) Carbopol^® hydrogels containing 5% (w/w) DMSO or 70% (w/w) ethanol and a compounded 10% (w/w) gabapentin Lipoderm^® formulation were able to facilitate permeation of the molecule across human skin. Further pre-clinical and clinical studies are required to investigate the topical delivery performance and pharmacodynamic actions of prospective formulations.