AAPS PharmSciTech

, Volume 12, Issue 4, pp 1209–1219 | Cite as

Understanding the Tendency of Amorphous Solid Dispersions to Undergo Amorphous–Amorphous Phase Separation in the Presence of Absorbed Moisture

  • Alfred C. F. Rumondor
  • Håkan Wikström
  • Bernard Van Eerdenbrugh
  • Lynne S. Taylor
Research Article


Formulation of an amorphous solid dispersion (ASD) is one of the methods commonly considered to increase the bioavailability of a poorly water-soluble small-molecule active pharmaceutical ingredient (API). However, many factors have to be considered in designing an API–polymer system, including any potential changes to the physical stability of the API. In this study, the tendency of ASD systems containing a poorly water-soluble API and a polymer to undergo amorphous–amorphous phase separation was evaluated following exposure to moisture at increasing relative humidity. Infrared spectroscopy was used as the primary method to investigate the phase behavior of the systems. In general, it was observed that stronger drug–polymer interactions, low-ASD hygroscopicity, and a less hydrophobic API led to the formation of systems resistant to moisture-induced amorphous–amorphous phase separation. Orthogonal partial least squares analysis provided further insight into the systems, confirming the importance of the aforementioned properties. In order to design a more physically stable ASD that is resistant to moisture-induced amorphous–amorphous phase separation, it is important to consider the interplay between these properties.

Key words

amorphous amorphous solid dispersion partial least squares (PLS) sorbed moisture 



Matthew J. Jackson is gratefully acknowledged for his help in collecting infrared results. This work is funded by Purdue Research Foundation and Merck Research Laboratories. This work was supported in part by a grant from the Lilly Endowment, Inc., to Purdue University School of Pharmacy and Pharmaceutical Sciences. BVE is a Postdoctoral Researcher of the ‘Fonds voor Wetenschappelijk Onderzoek’, Flanders, Belgium.


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Copyright information

© American Association of Pharmaceutical Scientists 2011

Authors and Affiliations

  • Alfred C. F. Rumondor
    • 1
  • Håkan Wikström
    • 2
  • Bernard Van Eerdenbrugh
    • 1
    • 3
  • Lynne S. Taylor
    • 1
  1. 1.Department of Industrial and Physical Pharmacy, College of PharmacyPurdue UniversityWest LafayetteUSA
  2. 2.Pharmaceutical DevelopmentAstraZeneca PharmaceuticalsMölndalSweden
  3. 3.Laboratory for Pharmacotechnology and BiopharmacyK. U. Leuven, Gasthuisberg O&N2LeuvenBelgium

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