Amorphous excipients

Exothermic Crystallization Precipitation Solidification Adsorption Solvent vapor induced crystallization of amorphous excipients Formation of salt forms of drug substances Melt granulation with semisolid excipients Solvent vapor sorption by drug substances... 

Moisture was known to increase the mobility of the surface groups of protein as measured by solid-state nuclear magnetic resonance spectroscopy The distribution of water between the protein and the excipients in a freeze-dried powder depends on the crystalline or amorphous nature of the excipients. For example, if a protein is formulated with an amorphous excipient and stored in a sealed container, water would distribute according to the water affinity of the protein and excipients.When the amorphous excipient crystallizes (e.g., because of elevated temperatures), it will expel its sorbed water, which may cause stability problems in the protein. ... 

Recombinant human growth hormone (rhGH) Mannitol and glycine as amorphous excipients to prevent human growth hormone (hGH) aggregation. Trehalose as a lyoprotectant, reserves the secondary structure of rhGH. [14]... 

Instability attributable to excipient-mediated water distribution in solids and powders has been explained by excipient physical properties. " Crystalline materials will not uptake moisture until the deliquescent point is reached. In contrast, amorphous excipients will absorb water until their glass transition temperatures fall below the ambient temperature when the mobility of the molecules has increased so much that excipient crystallization will occur to expel the absorbed water from the crystal lattice. Before crystal-... 

The relationship between the mechanical response of an individual particle to a directly applied stress and that of a powder of the particles is complex because the force transmission to an individual particle is mediated by other particles. As an example consider an amorphous excipient and assume the particles are spherical and have a mono-disperse size. The response to an applied stress of an individual particle should be independent of the direction of application as we re assuming the particle structure is isotropic (unlike a crystal which may exhibit a different response to stress in different directions due to the anisotropic structure dictated by periodic packing constraints). 

W. Abdelwahed, G. Degobert, and H. Fessi, Investigation of nanocapsules stabilization by amorphous excipients during freeze-drying and storage, European Journal of Pharmaceutics and Biopharmaceutics, 63 (2), 87-94, 2006. 

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