Transdermal delivery of ionic drugs by using ion-pair formation and microemulsion

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We first examined the enhancement of skin permeation of anionic diclofenac from non-aqueous vehicle isopropyl myristate (IPM) by ion-pair formation with either alkylamine or benzylamine as model counter ions. Permeation of diclofenac through excised guinea pig dorsal skin increased in the presence of these amines as well as solubility. Since the solubility of diclofenac was still limited, to obtain further enhancement of skin permeation, the effects of microemulsions as a vehicle for solubilizing the diclefonac-amine ion-pairs consisting of phosphate buffered saline, IPM, polyoxyethylene sorbitan monooleate and ethanol were examined. The microemulsions significantly increased diclofenac flux as well as its solubility. These findings indicated the usefulness of the combined use of ion-pair formation and microemulsion for the enhancement of skin permeation of ionic drugs. We also confirmed the enhancement of skin permeation of cationic ketotifen by ion-par formation by using alkylsulfonates such as 1-octanesulfonate as counter ions.We furthermore examined the usefulness of microemulsions for the improvement of the efficiency of intradermal delivery of polyphenols. The findings indicate the potential use of microemulsions for the intradermal delivery of polyphenols, especially for those such as quercetin and rutin which have relatively large molecular weights.The obtained results indicated the usefulness of ion-pair formation and microemulsion for transdermal snd intradermal drug delivery.