This study aimed to formulate semisolid niosomal encapsulated lidocaine and prilocaine using the patented palm oil base Hamin-C® for further characterization and in vivo pain assessment. Seven formulations were initially studied with various chemical compositions. A thin-layer film hydration method was used to produce niosome using a mixture of surfactant (Span® 40 or Span® 60) and cholesterol (CHOL) at a 1:1 ratio, with/without a charge-inducing agent (diacetyl phosphate) (DCP) and with/without labrasol®. Niosome F1 formulation had been identified as the highest %EE achieved, at 53.74 and 55.63% for prilocaine and lidocaine, respectively. Furthermore, NIO-HAMIN F1 emulgel indicated the best formulation with higher permeability of prilocaine and lidocaine compared to the rest of the formulations. The reformulation of optimization of NIO-HAMIN F1 emulgel using a cold process to NIO-HAMIN F1-C emulgel to improve the viscosity resulted in higher diffusion of prilocaine and lidocaine by 5.71 and 33.38%, respectively. In vivo pain perception studies by verbal rating score (VRS) and visual analogue score (VAS) on healthy subjects show a comparable local anesthetic effect between NIO-HAMIN F1-C emulgel and EMLA® cream.
Keywords: lidocaine; local anesthetic; nanoparticles; niosome; prilocaine; topical drug delivery.