Possibilities of the microemulsion use as indomethacin solubilizer and its effect on in vitro and ex vivo drug permeation from dermal gels in comparison with transcutol

Transcutol ® is a perfect solubilizer and an effective permeation enhancer of many active substances commonly used in cosmetics. Microemulsions due to the content of surfactant and co-surfactant could be also considered as chemical permeation enhancers that may support transdermal delivery of poorly water- soluble drugs. The purpose of this study was to investigate the effect of Transcutol ® and potential microemulsions on diffusion of poorly soluble indomethacin through an artificial membrane and excised rat skin. After drug solubilization in different enhancers, drug was dispersed in sodium alginate or carbopol gel used as dermal basis. For characterization of the microemulsions, the basic physico-chemical properties were determined. In vitro as well as ex vivo drug release was determined by vertical Franz cells. Enhancing effect of the examined microemulsions was observed only in carbopol gel. There was an increase in cumulative drug amount released through synthetic membrane by 37.7-39.8% from the microemulsion formulation and 90.6% from Transcutol ® formulation within 6 h compared to the control samples. The differences between the permeation curves with or without the content of the enhancers were statistically significant (p 0.9) between in vitro and ex vivo drug release from all dermal vehicles used. It can be stated that Transcutol ® is the best solubilizer and also penetration enhancer from the examined, and therefore it seems to be effective excipient/solubilizer in topical IND formulation.