Ion-paired Drug Delivery: An Avenue for Bioavailability Improvement

Ion-pairing is reported to improve the lipophilicity and subsequently the transport rate of polar drugs across lipid membranes. Lipophilisation of ionic drugs with high aqueous solubilities by ion-pair formation with appropriate counter-ion have proven to be promising for several applications. The aim of this review is to present the usefulness of ion-pair for improving the poor bioavailability of ionic drugs through various routes. The review covers an update on the applications of this strategy to improve drug delivery through various routes of administration including ocular, oral, parenteral and transdermal. It is discussed how ion-pair complexes assist in introducing functionality that would allow formation of a neutral molecule which can be subsequently encapsulated into delivery systems to be distributed by various routes of administration.