Heat Treatment Induced Specified Aggregation Morphology of Metoprolol Tartrate in Poly(ε-caprolactone) Matrix and the Drug Release Variation

Hot-melt blending has been widely used in the pharmaceutical industry to produce drug delivery systems, however, realizing the controlled drug release behavior of a hot-melt blended medicament it is still a tough challenge. In this study, we developed a simple and effective heat treatment method to adjust the drug release behavior, without the addition of any release modifiers. Thin metoprolol tartrate (MPT)/poly(ε-caprolactone) (PCL) tablets were prepared through hot-melt processing, and different morphologies of MPT were obtained by altering processing temperatures and the following heat treatment. MPT particles with different particle sizes were obtained under different processing temperatures, and fibrous crystals of MPT were fabricated during the following heat treatment. Different morphological structures of MPT adjusted the drug diffusion channel when immersed in phosphate-buffered saline (PBS), and various drug release behaviors were approached. After being immersed for 24 h, 7% of the MPT was released from the blend processed at 130 °C, while more than 95% of the MPT were released after the following heat treatment of the same sample. Thus, flexible drug release behaviors were achieved using this simple and effective processing manufacture, which is demonstrated to be of profound importance for biomedical applications.