Drug Distribution meant the reversible amount of drug transferred from one part to another part inside the body. When a drug enters into systemic circulation by absorption, it is distributed into interstitial and intracellular fluids. The organ or tissue receives different quantity of drug doses and the drug is remained in the different organs or tissues for a variable amount of time. The distribution of a drug doses between tissues is reliant on vascular permeability, cardiac output, regional blood flow and perfusion rate of the tissue and the binding of drug to tissue and plasma proteins and its lipid solubility. pH partition also takes part in drug distribution. In highly perfused organs such as the liver, heart and kidney Drugs can be easily distributed. At perfused tissues like muscle, fat and peripheral organs drugs is distributed in small quantity. when the equilibrium is known the unbound drug present in plasma is distributed from the plasma to the tissue. Factors Affecting Drug Distribution: Particle size of the drugs, Proteins Binding, Surface area of the Drug, Excretion, pH, Temperature, Physical Volume of the Body Etc