Ionic liquid-iontophoresis mediates transdermal delivery of sparingly soluble drugs

Low solubility restricted transdermal penetration of drugs. We aimed to develop a novel ionic liquid-iontophoresis (IL-IS) technology and assess their efficacy and primary factors in facilitating transdermal drug delivery. Five choline-based ILs with different chain length were synthesized and validated, and the impact of IL and/or IS technology on transdermal penetration of model drugs were investigated. The results indicated that five groups of ILs synthesized in this study exhibited minimal level of toxicity, and the longer the chain of acid ligands of ILs, the greater the cytotoxicity. The longer chain of acid ligand was demonstrated superior solubilizing capabilities compared to the shorter chain. Cinnamic acid-choline-based IL ([Cho] [Cin]) significantly improved permeation of all three model drugs, and permeation quantity was linearly positively associated with the concentration of ILs. The 10 h cumulative permeation of aripiprazole applied with ILs alone was enhanced by about 14-fold when paired with IS, and the penetration was linearly positively associated with the concentration and current strength of the ILs. In vivo results indicated that IL and/or IS technology primarily facilitated drug penetration into the skin, with potential involvement of endocytosis in this process. This study demonstrated that [Cho] [Cin] exhibited a significant enhancement in the transdermal delivery of three sparingly soluble drugs. It further enhanced the transdermal permeation of weak base drug following with the combining IL and IS technology. These findings highlighted that the IL-IS technology holded promise for facilitating the transdermal delivery of sparingly soluble and weak base drugs.