Formulation development of matrix type transdermal patches containing mefenamic acid: physicochemical characterization and in vitro release evaluation

Abstract

This research prepared the matrix type transdermal patches for mefenamic acid using ethylcellulose and Eudragit®RL as matrix layer and diethyl phthalates as plasticizer. They were prepared by dissolving all ingredients in the solvent and homogeneously mixing with the mefenamic acid powder by mechanical stirrer. Then, they were sonicated and poured into a Petri dish, and subsequently dried in hot air oven at 50 ± 2 °C. The mefenamic acid-loaded transdermal patches were evaluated and characterized by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and in vitro release. We found that crystallization of mefenamic acid affected the patches. However, when we increased the Eudragit®RL ratio as matrix layer, we found lower crystals characteristic of mefenamic acid in matrix patches. This was due to the fact that mefenamic acid could be dissolved in Eudragit®RL polymer more than ethylcellulose. The mefenamic acid powder showed the melting temperature at 233.50 °C; however, all matrix patches exhibited the melting point of mefenamic acid. The release profile showed a decrease of mefenamic acid release with increased Eudragit®RL ratio as a matrix layer. Thus, when increased the Eudragit®RL ratio, these matrix patches could reduce the crystalline effect of mefenamic acid, but it showed low release behavior of mefenamic acid from patches and was difficult to build the complete patches. The release behavior of all mefenamic acid patches followed the Higuchi’s model. The mefenamic acid patches could be easily prepared by simple method; however, in the future, these matrix patches will be developed to improve the crystallization effect of mefenamic acid.