Compounded Topical Gabapentin for Neuropathic Pain: Does Choice of Base Affect Efficacy?

The objective of this study was to investigate the effect of Lipoderm Cream, VersaBase Gel, and Emollient Cream on the release and permeation of gabapentin formulated for neuropathic pain. Gabapentin of different strengths (1%, 5%, and 10%) was compounded with the bases, diffusion of the drug from thebases, and permeation through artificial skin model studied with Franz diffusionsystem. Steady-state flux, cumulative permeation, and lag times were calculated,and release mechanisms modelled with first order, second-order, Higuchi, Korsmeyer-Peppas, and Hixon-Crowell kinetic models. Gabapentin recovery from VersaBase Gel, Lipoderm Cream, and Emollient Cream was 100.8 ± 2.7%, 101.3 ± 1.2%, and 104.9 ± 3.3%, respectively. Gabapentin completely diffused out of the three bases within 6 hours of application according to the Higuchi model. Flux of the drug appeared to be concentration-dependent with no permeation occurring at 1% strength. Whereas, 5% and 10% strengths in Lipoderm Cream permeated the skin rapidly, the same concentrations in Emollient Cream and VersaBase Gel required 60-minutes and 120-minutes lag times, respectively. For the three bases, a strong correlation was observed between lag times and flux. The overall permeation in VersaBase Gel and Lipoderm Base was not significantly different (P>0.05). However, Emollient Cream resulted in a significantly lower total permeation compared to other bases (P<0.05). As the formulations are for pain management, products with no lag times and higher flux are preferable. Although VersaBase Gel and Emollient Cream displayed some gabapentin permeability, it is important to consider gabapentin stability in these bases prior to use.