Amiloride, a diuretic used for managing resistant hypertension, is hindered by low oral bioavailability and Gastrointestinal side effects, impacting patient compliance. This study investigates transdermal delivery as an alternative to reduce pill burden and improve adherence. Using dermatomed porcine ear skin, the research examined the passive transdermal delivery of amiloride and the effect of various chemical enhancers, including oleic acid, oleyl alcohol, tocopheryl polyethylene glycol succinate, and N-methyl-2-pyrrolidone, individually or in combination. A validated High-Performance Liquid Chromatography method, adhering to Internal Council for Harmonized guidelines (ICH), was employed for quantitative analysis. In vitro permeation studies, conducted using porcine skin and Franz diffusion cells over 168 hours, revealed that oleyl alcohol (761.86±74.97 µg/cm²) and oleic acid (691.90±78.59 µg/cm²) were the most effective enhancers. These findings suggest that chemical enhancers can significantly facilitate the transdermal delivery of amiloride, offering a promising alternative to enhance patient compliance and achieve better therapeutic outcomes.

The world-wide transdermal drug delivery market is quite large, but only a small number of agents have FDA approval. The primary reason for such limited development is the difficulty in permeating the stratum corneum layer of human skin. In our study, we developed a novel percutaneous delivery enhancing approach. Magainin peptide was previously shown to disrupt vesicles from stratum corneum lipid components and this ability of magainin allows us to propose that magainin can increase skin permeability. Therefore, we tested the hypothesis that magainin, a pore-forming peptide, can increase skin permeability by disrupting stratum corneum lipid structure and that magainin¡¯s enhancement requires co-administration of a surfactant chemical enhancer to increase magainin penetration into the skin. In support of these hypotheses, synergistic enhancement of transdermal permeation can be observed with magainin peptide in combination of N-lauroyl sarcosine (NLS) in 50% ethanol-PBS solution. The exposure to NLS in 50% ethanol solution increased in vitro skin permeability to fluorescein 15 fold and the addition of magainin synergistically increased skin permeability 47 fold. In contrast, skin permeability was unaffected by exposure to magainin without co-enhancement by NLS-ethanol. To elucidate the mechanism of this synergistic effect, several characterization methods such as differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray diffraction were applied. These analyses showed that NLS-ethanol disrupted stratum corneum lipid structure and that the combination of magainin and NLS-ethanol disrupted stratum corneum lipids even further. Furthermore, confocal microscopy showed that magainin in the presence of NLS-ethanol penetrated deeply and extensively into stratum corneum, whereas magainin alone penetrated poorly into the skin. Together, these data suggest that NLS-ethanol increased magainin penetration into stratum corneum, which further increased stratum corneum lipid disruption and skin permeability. Finally, skin permeability was enhanced by changing the charge of magainin peptide via pH change. We modulated pH from 5 to 11 to change the magainin charge from positive to neutral, which decreased skin permeability to a negatively charged fluorescein and increased skin permeability to a positively charged granisetron. This suggests that an attractive interaction between the drug and magainin peptide improves transdermal flux.