Chemistry Reference
In-Depth Information
4
SOLID-STATE
CHARACTERIZATION OF
AMORPHOUS DISPERSIONS
Frederick G. Vogt
Morgan, Lewis & Bockius LLP, Philadelphia, PA, USA
4.1 INTRODUCTION
Pharmaceutical amorphous solid dispersions present unique challenges for analytical and
physical characterization. These challenges largely arise from the desire to characterize
the nature of interactions between the drugs and excipients used to form the dispersion,
detect low levels of recrystallization of the drug, and observe phase transformations upon
dissolution of the dispersion. The amorphous nature of the dispersion presents a hurdle to
analysis, because many of the major solid-state analytical techniques used in pharma-
ceutical development are most effective in applications to crystalline systems [1]. While
some of these techniques can be used to characterize dispersions in the same manner as
crystalline systems, they often require adaptation to allow for useful applications to
amorphous solid dispersions. Currently, many analytical techniques are available to
address the characterization challenges compared with other approaches to drug
formulation, and research continues into new approaches.
This chapter reviews established and emerging analytical and physical techniques
for the characterization of amorphous solid dispersions. Many of the techniques
reviewed here are spectroscopic in nature and probe the interaction of electromagnetic
fields of different energies with the sample of interest. Spectroscopic techniques access
molecular or atomic energy levels, which in molecular solids are primarily dependent on
