ABSTRACT
In the previous discussions, it was assumed that the drug is rapidly distributed to all parts of the body once it enters the systemic circulation. An immediate equilibrium is established between the drug in the systemic circulation and the drug in all parts of the body. The drug concentration in different parts of the body is different because of the differences in drug afnity to the different tissues. However, any change in the plasma drug concentration due to drug absorption or drug elimination is accompanied by a proportional change in the drug concentration in the different tissues. So the drug concentration-time proles in the different parts of the body are parallel to each other. The rapid distribution equilibrium achieved between the different tissues makes the body act as one homogenous compartment.
