Investigation of drug ionic liquid salts for topical delivery systems

Abstract

Pharmaceutical companies and FDA (Federal Drug Administration) rules rely heavily on crystalline active pharmaceutical ingredients delivered as tablets and powders in the form of neutral compounds, salts and solvates of neutral compounds and salts. About half of all drugs sold in the market are in the form of salts which are held together by ionic bonds along with some other forces. Recently, Ionic liquids (ILs) an interesting class of chemical compounds have offered potential opportunity for exploration as novel drug ionic liquid salts, particularly in the field of transdermal/topical drug delivery. Due to the multifunctional nature of these salts they could allow generation of new pathway to manipulate the transport and deposition behaviour of the drug molecule. It is this modular approach of IL that forms the basis of the research presented here, in which pharmaceutically acceptable compounds are combined with selected drugs with known problems. IL salts were generated by combining at least one drug molecule with FDA approved compounds and were assessed for physicochemical properties, skin deposition and permeation studies. Skin deposition data suggested that these systems exhibit high skin retention, which was found to correlate with the molecular weight. On the other hand, permeation data displayed an inverse relationship between flux values and molecular weight of the permeant. Similar work was extended with ILs with mixed anions containing two drugs. The benzalkonium-sulfacetamide ILs were investigated for synergism and the biological studies data display no synergistic effect. It was also illustrated that in-situ IL based ibuprofen hydrogels systems could be manipulated via IL approach for topical application. These findings suggest the potential applicability of IL based formulations for topical delivery of drugs.