Residual film formation after emulsion application: understanding the role and fate of excipients on skin surface

This study focuses on the fate of excipients contained in topical emulsions once applied on the skin. The aim was thus to develop a methodology to characterize the residue left on the skin shortly after emulsion application. To this end, both the role and the impact of the different excipients on the formation and properties of the residue left on the skin surface once a product is applied were investigated.

Highlights

• In vivo biophysical methods to describe the residue left on skin.

• Influence of the emulsion composition on the residue properties.

• The aqueous phase is still present on skin 15 minutes after emulsion application.

• The oily phase forms a durable hydrophobic and bright film on skin surface.

• Ingredients stratification on skin surface after application the emulsion.

To that purpose, an O/W emulsion composed of an ester as oily phase, an emulsifier (alkylpolyglucoside-based vehicles), a polymer and a humectant (hydrophilic excipient) was first developed. Then, systems with fewer ingredients were prepared to understand their respective role in the residual film. This residual film was studied in vivo by means of biophysical instrumental methods, all being performed on the participants’ forearm. Results highlighted the major role of the ester giving a bright and hydrophobic residue. While the surfactant structuration as the presence of glycerin and polymer provided a specific water distribution inside the residue on the skin surface. Finally, this work evidenced the ingredients organization in the residue depending on the systems composition, with a particular stratification on skin surface which could be considered in the formulation strategy for efficient active delivery and skin protection. More on residual film formation after emulsion application

Author links open overlay panelElodie Faucheux, Céline Picard, Michel Grisel, Géraldine Savary
International Journal of Pharmaceutics
https://doi.org/10.1016/j.ijpharm.2020.119453