Pharmacokinetics, a subfield of pharmacology, is the study of drug absorption, distribution, metabolism, and excretion kinetics, including the magnitude and speed of each of these processes. The Greek elements “pharmakon” (drug) and “kinesis” (movement) are the origin of the English term “pharmacokinetics,” which describes the movement of a drug. Pharmacokinetics is the mathematical study of the time-dependent variation in medication concentrations. So, to sum up, pharmacokinetics is the study of how medications enter, travel through, and are eliminated from the body by means of metabolism and excretion. Pharmaceuticals depend on pharmacokinetics research since it determines the dosage, mode of administration, time of peak effect, duration of action, and frequency of drug administration. Principles of pharmacokinetics center on variations in drug concentration brought about by drug absorption, distribution, and elimination throughout time. There are two primary ways that drugs and chemicals get beyond biological membranes: simple transfer and specialized transport. The process by which an unaltered medication enters the bloodstream from the place of administration is known as absorption. Due to the porosity of the capillaries, even big lipid-insoluble or ionized medicines are absorbed, whereas lipid-soluble medications readily pass through the capillary endothelium. The process by which medications enter extravascular fluids and tissues and leave the bloodstream is known as distribution. This critical pharmacokinetic phase affects not only the organs involved in metabolism and excretion but also the way that medicines reach their target areas. The process of changing a substance’s chemical form to one that is more water soluble for simpler excretion is called metabolism. Particularly, “biotransformation” describes the chemical alterations that foreign substances go through in the body. There are two main stages of biotransformation. Phase I consists of processes involving oxidation, reduction, and hydrolysis that add or reveal tiny polar functional groups (such -OH and -NH2). In order to prepare lipid-soluble medications for Phase II reactions or direct excretion, this phase alters them to make them more polar. Conjugation is the process by which polar endogenous compounds (such as sulfate or glucuronic acid) are joined to medications or their Phase I metabolites in Phase II. This step results in readily excreted conjugates that are soluble in water. The process of permanently eliminating medications and their metabolites from the body is called excretion. Water-soluble and ionized compounds are excreted more readily by excretory organs—apart from the lungs—than lipid-soluble ones, which must first be converted into water-soluble forms in order to be excreted more easily. The drug’s concentration in the body has an impact on pharmacokinetic processes (ADME), and how that concentration influences the process rate is known as the process order. Key pharmacokinetic parameters may be computed and the time course of medications in the body can be expressed quantitatively using pharmacokinetic models. Pharmacokinetics is determined by three factors: elimination, distribution and absorption.