Supplementary Material for: The Influence of the Acyl Chain on the Transdermal Penetration-Enhancing Effect of Synthetic Phytoceramides

<b><i>Background/Aims:</i></b> The skin has become very attractive as a route for drug administration. Optimization of topical drug formulations by the addition of penetration enhancers may facilitate the passage of drugs through the stratum corneum. <b><i>Methods:</i></b> In this paper, the skin penetration effect of phytosphingosine and 9 derived phytoceramides (PCERs) on 3 transdermal model drugs (i.e. caffeine, testosterone, ibuprofen) was investigated via Franz diffusion cell experiments using split-thickness human skin. Azone was included as a positive control. <b><i>Results:</i></b> The main finding in our study was that the PCERs exerted a compound-dependent penetration-enhancing effect. Some of the investigated PCERs exhibited a penetration-enhancing ratio of more than 2 (mean ± SE): for caffeine PCER1 (2.48 ± 0.44), PCER2 (2.75 ± 0.74), PCER3 (2.62 ± 0.93) and PCER6 (2.70 ± 0.45) and for testosterone PCER1 (2.08 ± 0.56), PCER2 (2.56 ± 0.13), PCER3 (3.48), PCER4 (2.53), PCER5 (2.04 ± 0.14), PCER6 (2.05 ± 0.48) and PCER10 (4.84 ± 0.79), but none of them had an influence on ibuprofen. <b><i>Conclusion:</i></b> The investigated PCERs exhibited a penetration-enhancing effect on caffeine and testosterone but not on ibuprofen.