Dynamic Transit Models

ALAN TALEVI

The ADME Encyclopedia. A Comprehensive Guide on Biopharmacy and Pharmacokinetics

Springer Nature

Año: 2022; p. 453 - 462

Intestinal drug absorption is a complex phenomenon that depends on a myriad of factors, including intrinsic physicochemical factors of the drug, such as solubility, pKa, and lipophilicity; physiological factors such as pH, gastric emptying, and intestinal transit times; and dosage form factors, such as the rate of drug release. The models that describe and/or predict the intestinal absorption of drugs can be classified, based on their dependence on spatial and temporal variables, as quasi-equilibrium models, steady-state models, and dynamic models [1]. Quasi-equilibrium models are independent of temporal and spatial variables; noteworthy among them are the classic pH-partition theory (see ?pH Partition Theory? entry) or the absorption potential [2], which provide a basic (though limited) guideline for the understanding of absorption trends. Steady-state models depend on the spatial variable, though not on the temporal variable; the film model and mass balance approximations [3, 4, 5] are examples of steady-state approaches and are useful to predict the fraction of the dose absorbed. At last, dynamic models are dependent on a temporal variable and can be used to predict the fraction of the dose absorbed and the rate of absorption, and to evaluate plasma concentration profiles [1, 6].Dynamic models include dispersion models, the mixing tank models, and transit compartment absorption models.