Related Experiment Video
Updated: Apr 19, 2026

Development, Characterization, and Evaluation of CAGE-based Ionic Liquid Systems for Transdermal Delivery
Published on: September 26, 2025
Ionic liquid versus prodrug strategy to address formulation challenges
Anja Balk1, Toni Widmer, Johannes Wiest
1Institute for Pharmacy, Am Hubland, University of Würzburg, 97074, Würzburg, Germany.
Purpose:
A poorly water soluble acidic active pharmaceutical ingredient (API) was transformed into an ionic liquid (IL) aiming at faster and higher oral availability in comparison to a prodrug.
Methods:
API preparations were characterized in solid state by single crystal and powder diffraction, NMR, DSC, IR and in solution by NMR and ESI-MS. Dissolution and precipitation kinetics were detailed as was the role of the counterion on API supersaturation. Transepithelial API transport through Caco-2 monolayers and counterion cytotoxicity were assessed.
Results:
The mechanism leading to a 700 fold faster dissolution rate and longer duration of API supersaturation of the ionic liquid in comparison to the free acid was deciphered. Transepithelial transport was about three times higher for the IL in comparison to the prodrug when substances were applied as suspensions with the higher solubility of the IL outpacing the higher permeability of the prodrug. The counterion was nontoxic with IC50 values in the upper μM / lower mM range in cell lines of hepatic and renal origin as well as in macrophages.
Conclusion:
The IL approach was instrumental for tuning physico-chemical API properties, while avoiding the inherent need for structural changes as required for prodrugs.
Related Concept Videos
Prodrugs
Prodrugs help overcome...
Bioavailability Enhancement: Drug Permeability Enhancement
Drug Delivery Systems: Different Types
Pharmaceutical Alternatives: Polymorphic Form-Related and Particle Size-Related Therapeutic Nonequivalence
Oral Drug Delivery Systems: Introduction
Bioavailability Enhancement: Determination and Conceptual Approaches in Overcoming Bioavailability Problems

