Development of a prospective isopropyl alcohol-loaded pharmaceutical base using simultaneous in vitro/in vivo characterization methods of skin performance

Abstract

Context: Approaching of pharmaceutical and cosmetic industries in some aspects inevitably influence formulation of topical pharmaceuticals, urging researchers to introduce novel excipients with proven benefits over traditional ones. In that context, alkyl polyglucosides (APG) emerge as prominent natural-origin emulsifiers with numerous favorable features (biodegradability, dermatological acceptability, desirable sensory properties).

Objective: To evaluate APG-stabilized bases (alone and upon addition of isopropyl alcohol) and their impact on skin performance. A simultaneous in vitro/in vivo skin absorption study was conducted to evaluate whether the tape stripping technique could be recommended as an in vivo tool for skin penetration assessment during formulation optimization process.

Materials and methods: After a comprehensive physicochemical characterization, biopharmaceutical properties of APG-bases versus reference ones were assessed through a combined in vitro (release/permeation) and in vivo approach.

Results and discussion: Physicochemical characterization revealed substantial difference in structural ordering due to the formation of various mesomorphic phases. The enhancer-loaded APG base resulted in significantly higher drug levels at all depths into the stratum corneum, indicating that the selected enhancer along with specific colloidal structure has increased the extent of drug delivery.

Conclusion: Results recommend the investigated emulsifier for stabilization of topical drug delivery systems, not only for their ability to sustain the addition of isopropyl alcohol which proved to be a valuable enhancer, but also satisfactory skin absorption and tolerability when compared to samples stabilized by conventional emulsifier. Tape stripping proved to be a useful and yet inexpensive tool for in vivo trials, able to discriminate subtle differences in dermal availability.

• Alkyl polyglucosides
• artificial skin constructs, Franz diffusion cells, isolated stratum corneum, tape stripping

Acknowledgements

The authors are grateful to Mr Klaus Weyhing from the Institute of Pharmaceutical Technology, Eberhard-Karls University in Tübingen for professional assistance.