A study of the in vitro diffusion kinetics of acetylsalicylic acid using the Sartorius absorption simulator

A unidirectional transport condition is often assumed when studying the in vitro diffusion of drugs. The present work describes a kinetic model that can be applied to beyond the first diffusion period. Acetylsalicylic acid was chosen as a model substance and its in vitro diffusion was studied using the Sartorius absorption simulator. The results of the two kinetic models (unidirectional and bidirectional) were in good agreement with each other. The curvature of the corrected substance concentration in the artificial plasma versus time plot can be used as a warning signal to detect passage beyond the first diffusion period.