The chapter focuses on the general principles of pharmacokinetics (PK) and pharmacodynamics (PD) that are relevant for the therapeutic use of drugs. The definition of the LADME model and explaining the term of the compartmental models contribute to understand the behavior and properties of these agents. Pharmacodynamics refers to general considerations of how a drug affects the organism. This includes drug-receptor affinity as well as interactions with molecular targets. Consideration of blood concentration versus time curves is assumed to be highly beneficial for predictions for both therapeutic and toxic drug actions.