Pharmaceutical Research

, Volume 27, Issue 4, pp 521–526 | Cite as

Crystalline vs. Ionic Liquid Salt Forms of Active Pharmaceutical Ingredients: A Position Paper

  • Jelena Stoimenovski
  • Douglas R. MacFarlane
  • Katharina Bica
  • Robin D. Rogers


Why not consider liquid salt forms of active pharmaceutical ingredients (APIs) as an alternative versatile tool in the pharmaceutical industry? Recent developments have shown that known APIs can be readily converted into ionic liquids and that these novel phases often possess different properties (e.g., improved solubilities and dissolution rates), which may have a direct impact on the pharmacokinetics and pharmacodynamics of the drug. They may also offer the potential of novel and more efficient delivery modes, as well as patent protection for each of the new forms of the drug. Since these pharmaceutically active ionic liquids represent a thermodynamically stable phase, they avoid the troublesome issues surrounding polymorphism and “polymorphic transformation.” In some cases, an active cation and an active anion can be combined to produce a liquid possessing dual functionality. Here we examine and challenge the current industry reliance on crystalline APIs by discussing the breadth and potential impact of liquid salts as a possible approach to phase control.


active pharmaceutical ingredient delivery modes ionic liquid polymorphism salt 



DRM is grateful to the Australian Research Council for his Federation Fellowship.


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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Jelena Stoimenovski
    • 1
  • Douglas R. MacFarlane
    • 1
  • Katharina Bica
    • 2
    • 3
  • Robin D. Rogers
    • 2
    • 3
  1. 1.Monash UniversityClaytonAustralia
  2. 2.The Queen’s University of BelfastBelfastUK
  3. 3.The University of AlabamaTuscaloosaUSA

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