Effect of monoacyl phosphatidylcholine content on the formation of microemulsions and the dermal delivery of flufenamic acid

The choice of appropriate excipients is crucial for the success of a dermal drug delivery system. Especially surfactants should be chosen carefully, because of their possible interactions with the skin or the applied drug. Since monoacyl phosphatidylcholine (MAPL) exhibits great emulsification properties and can be derived from natural sources, it is of great interest as surfactant in microemulsions. Therefore, the aim of the present study was to investigate the effect of the MAPL content on the formation of microemulsions. The great emulsification power of MAPL was confirmed by increased isotropic areas with increasing MAPL content. Moreover, a decrease in particle size, particle size distribution and viscosity with increasing MAPL content was determined. Besides its effects on microemulsion structure, MAPL exhibited a significant influence on the skin permeation of flufenamic acid. Interestingly, the higher the MAPL content, the lower was the skin permeation of flufenamic acid. A possible explanation might be that the hydrophilic MAPL could hinder the permeation of the lipophilic drug. In contrast, the skin permeation enhancing effects of the microemulsion with the lowest MAPL content might be attributed to formation of a patch-like structure and therefore better contact between the formulation and the skin.

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