PK/PD modeling (pharmacokinetic/pharmacodynamic modeling) (alternatively abbreviated as PKPD or PK-PD modeling) is a technique that combines the two classical pharmacologic disciplines of pharmacokinetics and pharmacodynamics. It integrates a pharmacokinetic and a pharmacodynamic model component into one set of mathematical expressions that allows the description of the time course of effect intensity in response to administration of a drug dose. There are a variety of PK/PD modeling approaches, but there are only five major classes: \n* Direct link PK/PD models \n* Indirect link PK/PD models \n* Indirect response PK/PD models \n* Cell Lifespan models \n* Complex response models