Stephen W. Hoag, PhD

I have two main areas of research; the first area involves developing systematic methods for formulating controlled and immediate release tablets. Tablet Press Instrumentation: By using computers and an instrumented tablet press to monitor tablet compaction, mathematical models can be derived that describe the tablet compaction process. These models serve as a basis for improving our understanding of tablet compaction and the mechanical stability of a tablet formulation. To conduct this research students who work in my laboratory become familiar with: tablet press operation, tablet press instrumentation and the design of instrumentation using finite element analysis (FEA), PC-based data acquisition systems and mathematical modeling. Formulation of Nutritional Supplements and Botanical Products: As an extension of this formulation research, we are also examining the formulation of folic acid containing multivitamin and mineral supplements. In a study conducted in our laboratory we found that 66% of the prenatal vitamins we tested failed to meet the USP dissolution specification for folic acid. Given the significant health implications of folic acid in the prevention of neural tub defects we are trying to determine why so many products failed and what can be done to improve their formulation. Students who conduct this research will become familiar with dissolution testing, determination of intrinsic dissolution rate for vitamins and the formulation of nutritional supplements and complex botanical products. Shear Cell Analysis and Formulation Scale-Up: As a new area of research we are trying to correlate critical states in a powder bed with problems found during the scale-up of a formulation. Film coating polymers: we examine the interactions between common excipients and the film coating polymers and film coating dispersions.

The second area of research involves the use of mathematical models to understand the mass transport processes in hydrogels. Typically hydrogels are used as diffusion barriers to either control the rate of release or to keep incompatible components of a system separated. Thus, the understanding of the diffusional properties of these gels is critical to their successful application. Studies to date have examined the factors that lead to heterogeneous Ca alginate gel formation and the release of bioactive molecules from these heterogeneous calcium alginate gels. Also, we have examined silk-elastinlike protein polymers and the effects of solute charge and hydrophobicity on the release from the protein polymers.