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Modeling Solvent Evaporation During the Manufacture of Controlled Drug Release Coatings and the Impact on Release Kinetics



James A. Warren, D M. Saylor, Martin McDermott, D Patwardhan, Chang-Soo Kim


To improve functionality and performance, controlled drug release coatings comprised of drug and polymer are integrated with traditional medical devices, e.g. drug eluting stents. Depending on manufacturing conditions, these coatings can exhibit complex microstruc- tures. Previously, we developed a thermodynamically consistent model for microstructure evolution in these systems to establish relationships between process variables, microstruc- ture, and the subsequent release kinetics. Calculations based on the model were, in general, consistent with experimental findings. However, because of assumptions regarding the evap- oration of solvent during fabrication, the model was unable to capture variations through the coating thickness that are observed experimentally. Here, we introduce a straightforward method to incorporate solvent evaporation explicitly into the model. Calculations are used to probe the impact of solvent evaporation rate and drug loading on the microstructure that forms during manufacturing and subsequent drug release kinetics. We find that the predicted structures and release kinetics are consistent with experimental observations. Further, the calculations demonstrate that solvent evaporation rate can be as critical to device perfor- mance as the amount of drug within the coating. For example, changes of a factor of five in the amount of drug released were observed by modifying the rate of solvent evaporation during manufacturing.


controlled drug release, drug delivery, modeling, microstructure, stent, composite, confocal microscopy


Warren, J. , Saylor, D. , McDermott, M. , Patwardhan, D. and Kim, C. (2009), Modeling Solvent Evaporation During the Manufacture of Controlled Drug Release Coatings and the Impact on Release Kinetics, Biomaterials, [online], (Accessed June 20, 2024)


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Created August 1, 2009, Updated February 19, 2017