Formulation of Topical Pregabalin for the Treatment of Neuropathic Pain
Halima Ahmad Ibrahim Thwaib
حليمة أحمد ابراهيم ذويب
Pregabalin is an anticonvulsant drug used to treat epilepsy and neuropathic pain associated with diabetic peripheral neuropathy and post-herpetic neuralgia marketed by Pfizer under the brand name Lyrica®. It is available in capsules, oral solution, and extended-release tablets and is associated with a number of undesirable side-effects especially on the kidneys. The aim of this study is to develop pregabalin microemulsion for topical treatment of neuropathic pain in order to overcome the troubles associated with its oral delivery and to investigate the effect of different PEs on drug permeation rate. The experimental studies had been implemented in three stages: the first stage, the construction of pseudo-ternary phase diagram using aqueous titration method. The microemulsions were formulated using different oil phases such as oleic acid, IPM and R(+)-Limonene oil which were also used as PEs, 0.1 M pregabalin as the aqueous phase with PG in different ratios. Tween 80 as the surfactant and ethanol as the cosurfactant which were used in different ratios. The second stage, the selection of microemulsion formulations: three systems (B,H and N) were selected to figure out the best PE among the three oils (Oleic acid, IPM and R(+)-Limonene) according to the highest permeability coefficient value (P) and three other systems (E,K and Q) were selected to choose the system having the highest permeability coefficient (P) in the presence of PG. The third stage is the diffusion study of the selected systems. Diffusion parameters that were determined: Cumulative amount of drug released per unit area (Mt), the lag time (TL), diffusion coefficient (D) ,the partition coefficient (K) and the permeability coefficient (P). Among the three systems (B,N and H), oleic acid was the best PE among the three oils since it has the highest permeability coefficient (P). On the other hand, between the three other systems (E, K and Q) system K has the highest permeability coefficient value (P) in the presence of PG. Which indicates that PG works synergistically with IPM in system K in enhancing the drug permeability. The results indicate that microemulsion formulation can be used as a feasible alternative to conventional formulations of pregabalin with advanced permeation characteristics for improved topical drug delivery. Short initial lag times were observed indicating that pseudo-steady state conditions were quickly achieved in all cases. Keywords: Pregabalin, neuropathic pain, microemulsion, topical drug delivery, Franz diffusion cell, penetration enhancer.