An in vitro method to predict the coating influence on esophageal adhesion and gliding performance of solid oral dosage forms

Purpose: The ease to swallow solid oral dosage forms (SODF) has become an emerging concern due to the growing age of the population and its incidence of swallowing problems. Alongside with the desired drug release profile, the ability to provide a non-adhesive surface of the SODF that can aid safe swallowing should be retained during pharmaceutical development. Previous studies have shown that current in vitro methods are not accurate in predicting the potential esophageal adhesion of SODF. This study proposes a fast and simple method to predict the influence of different coatings on the esophageal adhesion and mucus interaction (gliding) during swallowing and transit of SODF.
Methods: The in vitro model consisted of a Universal Testing Machine (Instron) in tension mode, equipped with a horizontal platform containing a defined sliding area. The measuring device was composed of a round disc containing a small metal hook that was attached to the measuring cell via a nylon cord. The cord passed through a metal wheel inserted in a height-adjustable column that was
aligned with the measuring head at a 90° angle. The mucosal environment of the oro-esophageal system was mimicked by fixing
lyophilized mucin across the total extent of the sliding area. For the measurements, the mucin-coated sliding area was moistened by
spraying water at 37 °C. An evaluation of the integrity of a single sliding area for several measurements was performed and different substrates were tested as mucin binders. The coatings to be tested were fixed to the lower surface of the disc and put into contact with the mucin layer by the left end of the sliding area. Subsequently, a defined weight (50 g) was placed over the disc and the load
required to glide the substrate across the mucin-based sliding area was measured and recorded with the equipment’s software.
Results: The method provided reproducible results of gliding behavior on the freshly prepared sliding area. The double-sided adhesive tape was seen as the best mucin-binding substrate and repetitive measurements with the same sliding area showed increasing variability in gliding properties. The obtained results on freshly prepared mucin layers showed different gliding behaviors for the investigated polymers, proving that the method might be a useful tool in predicting the impact of different coatings on the adhesion and gliding
performance during swallowing and esophageal transit of SODF.
Conclusion: The in vitro method developed in this work predicted different profiles of esophageal adhesion and gliding performance for the tested
polymers, proving to be a useful tool for the future development of safe-to-swallow coating technologies.