The biorelevant in vitro dissolution test (fasted-state gastric conditions followed by fed-state intestinal conditions) of the Singulair® granules mixed with milk scenario led to the best prediction of the in vivo drug performance in infants of all subgroups (1 to 3 months, 3 to 6 months and 6 to 24 months). Results from this study suggest that the in vivo studies were probably performed in the fed state or that the practice of medicine co-administration with food and drinks might have triggered fed-state conditions in vivo.