Ion-pair Formation as a Strategy to Enhance Topical Delivery of Salicylic Acid

An in‐vitro study was carried out to determine the possibility of improving the efficiency of transdermal delivery of salicylate through human epidermis by ion‐pair formers (alkylamines and quaternary ammonium ions). Further, the relationship between the physico‐chemical properties of the counter‐ions and salicylate flux was examined. It was found that flux can be related to the conductivity associated with the penetrant solution, molecular size of the counter‐ion and lipophilicity expressed as either octanol/water partition coefficient of the ion pairs or the carbon chain‐length of the counter‐ions. Equations have been developed to predict salicylate flux from these physicochemical parameters.