Optimization of minoxidil microemulsions using fractional factorial design approach

Abstract

The objective of this study was to apply fractional factorial and multi-response optimization designs using desirability function approach for developing topical microemulsions. Minoxidil (MX) was used as a model drug. Limonene was used as an oil phase. Based on solubility, Tween 20 and caprylocaproyl polyoxyl-8 glycerides were selected as surfactants, propylene glycol and ethanol were selected as co-solvent in aqueous phase. Experiments were performed according to a two-level fractional factorial design to evaluate the effects of independent variables: Tween 20 concentration in surfactant system (X₁), surfactant concentration (X₂), ethanol concentration in co-solvent system (X₃), limonene concentration (X₄) on MX solubility (Y₁), permeation flux (Y₂), lag time (Y₃), deposition (Y₄) of MX microemulsions. It was found that Y₁ increased with increasing X₃ and decreasing X₂, X₄; whereas Y₂ increased with decreasing X₁, X₂ and increasing X₃. While Y₃ was not affected by these variables, Y₄ increased with decreasing X₁, X₂. Three regression equations were obtained and calculated for predicted values of responses Y₁, Y₂ and Y₄. The predicted values matched experimental values reasonably well with high determination coefficient. By using optimal desirability function, optimized microemulsion demonstrating the highest MX solubility, permeation flux and skin deposition was confirmed as low level of X₁, X₂ and X₄ but high level of X₃.

• Desirability function
• fractional factorial design
• microemulsion
• minoxidil
• optimization

Declaration of interest

This study was supported by the Thailand Research Fund (MRG5480035), the Commission of Higher Education and Khon Kaen University, Ministry of Education, Thailand. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.