Aim of the review: relatively new European Union regulations on children's medicines have emphasised the need for scientists to consider paediatric populations during drug development. This requires an understanding of the physiology in the paediatric population compared to that of adults. In this review, data cited in the public literature on the gastrointestinal (GI) physiology that could affect drug absorption have been summarised to draw attention to some of the differences between adults and paediatric populations that can make predicting the pharmacokinetics of oral drugs in the paediatric population a complex task.
Method: a search for relevant articles was conducted using EMBASE, MEDLINE (through PubMed) and The National Institute for Public Health and the Environment. Additional journals were found from the references in the initial search results. Furthermore, a selection of common textbooks was used to fill in gaps in physiology data or understanding not covered by the journal articles found. Only data obtained from healthy individuals was used.
Results: information on the pH and transit time along the GI tract, as well as other GI physiology data was collated and summarised. There was less data available in the literature on the younger population partly as a consequence of the challenging ethics of carrying out invasive tests on healthy children.
Discussion and conclusion: it was found that considerable variability in physiology exists within the paediatric population. The pH and transit time of the GI tract varies with age, with the greatest changes occurring during the neonate's first month. Other GI physiology also varies with age potentially having an impact on drug absorption. This review highlights the variability of paediatric physiological values within the literature, indicating the difficulty in performing measurements in the paediatric population as well as the natural variability that exists in this age group.