In vitro simulation of realistic gastric pressure profiles

Novel in vitro dissolution tools can aid the development of orally administered drugs by explaining dosage form related in vivo phenomena that are not explainable with standard test apparatuses. Such novel tools are able to mimic various parameters in accordance with gastrointestinal conditions. Hereby, in vivo occurring pressure events were shown to be of major importance since they largely affect dosage form disintegration, drug dissolution and subsequently resulting drug plasma concentration profiles. The aim of the present study was to investigate the feasibility of producing biorelevant pressure events with standard test apparatuses and with the dynamic open flow through test apparatus. For this purpose, we used the SmartPill®, a swallowable capsule that houses a pressure sensor and that was already applied to gather human in vivo data. Among the standard apparatuses, highest pressures were measured in the reciprocating cylinder apparatus and the disintegration tester. No relevant pressure peaks could be detected in the paddle apparatus and the mini paddle apparatus. In contrast, the dynamic open flow through test apparatus enabled the simulation of complete gastric pressure profiles as they occur in vivo. The present work underlines the potential of novel in vitro dissolution models as useful tools during the drug development process as well as for explanatory purposes.

Mimicking the dynamic Colonic microbiota in vitro to gain a better understanding on the in vivo metabolism of xenobiotics: Degradation of sulfasalazine

Due to the potential effects of colonic metabolism, the interest in the composition and action of intestinal microbiota has increased significantly throughout the last 10 years. Recently focus is turning to the development and implementation of in vitro tools closely simulating in vivo colonic metabolic processes suitable for routine use. The aim of the present study is to compare the metabolization of the model drug sulfasalazine utilizing the novel dynamic bioreactor MimiCol and a standard static batch fermenter inoculated with cryopreserved faecal microbiota. Major advantages of the novel bioreactor MimiCol are the smaller media volume which is closer to in vivo conditions, the possibility to perform media changes and the closer simulation of in vivo mixing patterns. The study proved that the MimiCol is able to simulate the dynamic conditions found within the ascending colon. The dynamic conditions within the MimiCol led to an almost 2-fold increase of the metabolization rate constant in comparison to the static batch fermenter. Our study was able to prove that the novel dynamic bioreactor MimiCol is able to closely simulate physiologically relevant conditions.

Influence of Different Diets on the Degradation of Sulfasalazine by Colon Bacteria Determined Using MimiCol3

The microbiome of the colon is characterized by its great diversity. This varies not only intra- but also interindividually and is influenced by endogenous and exogenous factors, such as dietary and lifestyle factors. The aim of this work was to investigate the extent to which the degradation of the drug sulfasalazine is influenced by different microbiota. Therefore, the in vitro model MimiCol3 was used, which represents the physiological conditions of the ascending colon. In addition to a representative physiological volume, the pH value, redox potential and an anaerobic atmosphere are important to provide the bacteria with the best possible growth conditions. Stool samples were taken from three healthy subjects, comparing omnivorous, vegetarian and meat-rich diets, and cultured for 24 h. However, the nutrient medium used for cultivation led to the alignment of the bacterial composition of the microbiota. The previously observed differences between the diets could not be maintained. Nevertheless, the similar degradation of sulfasalazine was observed in all microbiota studied in MimiCol3. This makes MimiCol3 a suitable in vitro model for metabolism studies in the gut microbiome.