2021-04, Kuentz, Martin, Vinarov, Zahari, Bertil, Abrahamsson, Artursson, Per, Batchelor, Hannah, Berben, Philippe, Bernkop-Schnürch, Andreas, Butler, James, Ceulemans, Jens, Davies, Nigel, Dupont, Didier, Eide Flaten, Goril, Fotaki, Nikoleta, Jannin, Vincent, Keemink, Janneke, Kesisoglou, Filippos, Koziolek, Mirko, Augustijns, Patrick, Griffin, Brendan

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

2016-07-30, Machado, Alexandra H.E., Kokubo, Tohru, Dujovny, Gabriela, Jones, Brian, Scialdone, Claudio, Bravo, Roberto, Kuentz, Martin

Water is known to exhibit pronounced effects on lipid-based formulations (LBFs) and much research has focused on aqueous dispersion and dilution behavior regarding biopharmaceutical performance. From a product quality perspective, it is also critical to study a range of lower water amounts in formulations with respect to capsule filling. The present work addressed the need for a better understanding of LBF microstructure by taking percolation theory into account. The effects of increasing amounts of water on LBFs were analyzed by conductivity, water activity, time-domain nuclear magnetic resonance, and diffusing wave spectroscopy. Results were interpreted using percolation theory and preliminary mechanical tests were conducted on gelatin and hypromellose (HPMC) capsule shells. For both LBF systems, increasing water amounts led to marked changes in the microstructure of the formulations. Percolation laws could be fitted adequately to the data and thresholds were identified for the formation of continuous water channels (ϕwc~0.02-0.06). A new theoretical model was proposed for water activity. The preliminary shell material studies showed that the threshold for generating water channels in the formulation could be correlated to mechanical changes of the capsule shell that were relatively more pronounced in the case of gelatin. This mechanistic study demonstrated the importance of understanding and monitoring of microstructural changes occurring in LBFs with increasing amounts of water, which will help to design quality into the final dosage form.