Abstract: Models, systems, and methods that accurately predict an impact on drug absorption of foods present in the GI tract are described herein. One example embodiment is a computer-implemented pharmacokinetic model of absorption of an oral compound in a subject. The example computer-implemented model includes memory and a processor in communication with the memory. The memory includes a representation of the subject, a representation of the oral compound, and a representation of a co-administration agent to be consumed by the subject along with the oral compound. The processor is configured to simulate absorption of the oral compound in the subject based on the representation of the subject, representation of the oral compound, and representation of the co-administration agent. The processor is further configured to generate and store in the memory a representation of concentrations over time of the oral compound in blood of the subject.