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By Patrick Marsac

Marsac-finalSolid state characterization is a critical component for developing solid oral dosage forms. The pharmaceutical scientist must use all available tools and techniques at the forefront of materials science to best choose the materials that will optimize the performance of the solid oral dosage form and also the processing required to manufacture the finished product. In addition, the formulation must remain physically and chemically stable over the lifetime of the product.

Materials science and engineering principles play a key role in the pharmaceutical industry. Multiple tools and techniques are required to solve problems associated with phase changes induced by physicochemical interactions among the materials within the formulation, stresses imposed during manufacturing, and exposure to environmental stress post production. Also important are macroscopic changes that may arise during manufacturing, transportation, and storage.


The pharmaceutical scientist has many tools and techniques also that can help to determine physical changes, chemical instabilities, and the associated impact on quality and performance. For instance, amorphous forms of an API most often show inferior chemical stability as compared to the crystalline counterpart. In the case where delivery of a crystalline material is preferred, the formation of a fraction of amorphous material as a result of processing may impact chemical stability and perhaps dissolution rate. Therefore, the form in the formulation must be measured and shown to be consistent across the processing control space. Analytical tools exist which allow for the development of a fundamental understanding of how molecular motions are related to physical and chemical instabilities. Inherently, the chemical liabilities and the physical nature of the materials are linked and therefore should be considered in tandem if the goal is to uncover the fundamental mechanism of physical and chemical instability and therefore the associated risks with processing, performance, and quality.

In the cover article in the January issue of the AAPS Newsmagazine we highlight how chemical degradation and in vivo performance can be influenced by the excipients introduced, the complexities of physical changes in both the API and the excipients themselves, as well as the manufacturing process and storage conditions. Read Advanced Characterization of Solid Oral Dosage Forms: Linking Physical Changes to Measures of Performance and Quality, from the PPB section, and then participate in the discussion point below.

Advances in solid state analytics show the promise of orders of magnitude increase in both spatial resolution and speed. Would your business find value in the application of solid state measurements that would provide a link between physical changes and measures of performance in finished dosage forms?

Patrick Marsac, Ph.D., is an associate professor in the Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky.