DSC determinations in the complex showed enthalpy and temperature depressions, indicating KP and DOPC interaction. In addition, dipole-dipole interactions between the KP carboxylic acid and OH groups in phospholipids were shown by 1H NMR studies. Based on the NMR studies, a KP-DOPC binding model is proposed, in which KP is involved by the two long aliphatic chains of the phospholipid. Solubility studies indicated that DOPC improved drug solubility. KP permeation was enhanced by both formulations tested, but the complex also increased its skin uptake. Such behavior could be attributed to the solubilizing, melting and enhancing effects of DOPC. Skin irritation and hypersensitivity were not significantly changed compared to control, suggesting that the formulation may be therapeutically explored for KP transdermal delivery.