Synergistic Effects of Transcutol and Terpenes as Penetration Enhancers: In Vitro and In Vivo ATR-FTIR Spectroscopic Imaging Studies

The skin offers an ideal application site to deliver therapeutic agents for both topical and systemic effect. However, the integument is also a well-designed membrane to protect the organism from environmental factors, thus it is an effective obstacle for drug permeation. The main barrier for skin delivery is the stratum corneum (SC), the outermost layer of the epidermis. The SC is formed by dead and keratinized cells which present a unique barrier to passage of drugs across the skin [1, 2]. Several approaches are used to overcome the barrier property of SC in topical and transdermal administration of drugs, the most frequent of which is the inclusion of chemical penetration enhancers in formulations.