SimBiology lets you represent a model of a biological or a pharmacological mechanism just as you would draw it on a piece of paper. It includes a block diagram editor that lets you graphically build models by dragging and connecting blocks. You can also programmatically build and manage models using MATLAB functions.
In addition to the environment for building models, SimBiology includes a library of standard PK models. Or, you can import models from a Systems Biology Markup Language (SBML) file.