Friday, 29 April 2022 12:00

The Amorphous State – Friend or Foe of the Formulation Scientist?


The amorphous form is a disordered, high-energy form, compared to the crystalline counterpart.  Amorphous materials are of interest in pharmaceutical formulations since they frequently have
favourable biopharmaceutical properties such as enhanced solubility and dissolution. The amorphous state is energetically unstable however and can transform back to the crystalline phase.

Different unit processes, such as spray drying, milling and co-precipitation, may be used for preparing the amorphous form of active pharmaceutical ingredients (APIs). Co-processing of the API with a polymeric excipient to form an amorphous solid dispersion is frequently required in order to ensure the physical stability of the composite amorphous form and its desired performance in vivo. Rational approaches to the formulation and production of physically stable amorphous solid dispersions will be discussed in this presentation.

While milling can be used to purposefully generate the amorphous form, in pharmaceutical processing it often unintentionally induces disorder and defects on the surface of particles. The presence of even small amounts of amorphous material, and the tendency of the amorphous form to revert over time to the energetically favoured crystalline state has implications for processability, stability, and dosage form performance. Co-processing with crystalline excipients is a possible strategy for mitigating the generation of amorphous APIs. The potential of this approach to prevent amorphisation on milling and the selection of suitable excipients for the process will be discussed.

The amorphous state can be a help or a hindrance to the formulation scientist and thus its production and behaviour needs to be controlled and understood.


Anne Marie Healy is Professor of Pharmaceutics and Pharmaceutical Technolo y in the School of Pharmacy and Pharmaceutical Sciences, Trinity College Dublin. She has a B.Sc. in Pharmacy and a Ph.D. in Pharmaceutics, both from the University of Dublin. She joined the School of Pharmacy, TCD in 1992 as a Lecturer in Pharmaceutics. In 2010 she was elected Fellow of Trinity College.  Anne Marie has published extensively, with over 110 international peer reviewed publications.  She has graduated 21 PhD students and mentored 26 postdoctoral researchers.

Her research interests include pharmaceutical material science, preformulation and formulation of pharmaceuticals, amorphous solids, co-crystals, formulating poorly soluble drugs, pharmaceutical processing and pulmonary drug delivery. Anne Marie is a Co-Principal Investigator of the SSPC – the Science Foundation Ireland Research Centre for Pharmaceuticals ( and is one of the Co-Directors of the EPSRC-SFI Centre for Doctoral Training in Transformative Pharmaceutical Technologies (

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