PK; Is the study of how a drug is absorbed, distributed, metabolised, and excreted over time. Refers to what the body does to a drug, refers to the movement of drug into, through, and out of the body – the time course of its absorption, bioavailability, distribution, metabolism, and excretion. Pharmacodynamics ( Pharmacodynamics), described as what a drug does to the body, involves receptor binding, postreceptor effects, and chemical interactions. Drug pharmacokinetics determines the onset, duration, and intensity of a drug’s effect. Formulas relating these processes summarize the pharmacokinetic behavior of most drugs.