Development of particulate pulse-release formulations and their mathematical description

In this contribution both the development of a multi-particulate delayed release system and a mathematical model to describe its release properties are presented. The formulation consists of a water-soluble core coated with a water-insoluble ethylcellulose coating. After immersing the formulation in water, the coating will determine the rate of water uptake into the core. Due to the volume increase of the core, the coating will fail mechanically and the contents of the core will be released. The formulation has a pulse-release profile; i.e. a fast release of the contents is obtained after a pre-determined lag-time. Results of water sorption experiments are used to estimate the Maxwell–Stefan diffusion coefficients of water in the coating. The prediction of the release time based on the presented model is in good agreement with the experimental findings.