Mechanistic modeling of gastrointestinal motility with integrated dissolution for simulating drug absorption

A new computational method - the multiple moving plug (MMP) model - is described to simulate the effect of gastrointestinal motility and dissolution on the pharmacokinetic profile of any given drug. The method is physiologically more consistent with the experimental evidence that fluid exists in discrete plugs in the gastrointestinal tract, and therefore is more realistic than modeling the gastrointestinal tract as a series of compartments with first-order transfer. The number of plugs used in simulations, their gastric emptying times and volumes, and their residence times in the small intestine can be matched with experimental data on motility. In sample simulations, drug absorption from a series of fluid plugs emptied from the stomach at evenly spaced time intervals showed lower C_max and higher T_max than an equivalent dose emptied immediately as a single plug. To the extent that new techniques can establish typical ranges for the volumes of fluid emptied from the stomach and their respective timing, the MMP model may be able to predict the effect of gastric emptying on the variability seen in pharmacokinetic profiles. This could lead to an expanded safe space for the regulatory acceptance of formulations based on dissolution data.