Investigating the effect of whey and casein proteins on drug solubility from a paediatric drug absorption perspective

Considering the predominantly milk-based diet of neonates and infants and their immature gastrointestinal digestion, milk proteins may affect drug behaviour and absorption in this population. Using in vitro models, this study investigated the impact of the representative milk proteins, whey and casein, on the solubility and permeation of the lipophilic model drugs spironolactone, clopidogrel and ritonavir. Drug solubility experiments revealed that the presence of milk proteins increased drug solubility. Next, permeation studies demonstrated that the same milk proteins reduced drug permeation across an artificial membrane. These results highlight the importance of the solubility-permeability interplay and indicate the effect of these proteins may be considered during (paediatric) drug development. Lastly, the findings underscore the importance of considering milk protein-drug interactions to optimize drug delivery strategies during (paediatric) drug development and especially for the youngest and most vulnerable part of this population.