Hemodynamic and Clinical Results of Transcatheter Aortic Valve Replacement in Large Aortic Annuli: Experience of One Center of Latin America

Pharmacokinetic (PK) models have been designed to predict the transient relationship between the drug’s intended effect and the conditions of the drug’s application. This chapter considers a model of tissue scale drug delivery that represents three drug phases: the free drug in the extracellular space, the free drug in the intracellular space, and the intracellular product of reaction. A review is presented of the most common components used in the three-compartment continuum models of drug delivery to single cell-type populations. This is followed by a review of the field’s methods to model drug delivery to tissues composed of multiple cell-type populations. The remainder of this chapter focuses on the development of the analytical solution to the problem of the conservation of drug mass in a tissue composed of three types of cells. In this problem the transmembrane transport rates are represented by Fickian-based models and the internal reaction rates are represented by nonreversible first-order binding models. An uncoupling procedure is applied to the system of four equations that leads to a single partial differential equation of high order having the extracellular concentration as a single unknown. This equation is recognized to be a dual-phase-lag (DPL) equation of high order whose solution is formulated by using a modified separation-of-variable method. The results are presented in a graphical form using 2D and contour plots.