ABSTRACT
INTRODUCTION For effective drug therapy, it is necessary to deliver therapeutic agents selectively to their target sites since most drugs are associated with both beneficial effects and unwanted actions. In general, the lack of selectivity in action of most conventional drugs is closely related to their pharmacokinetic (PK) properties. The in vivo fate of a drug given by certain administration route is determined by both the physicochemical properties of the drug and the anatomical and physiological characteristics of the body. Basically, most conventional drugs diffuse freely throughout the body and show relatively even tissue distribution due to their low molecular weights.
