The Novel Parenteral Controlled Drug Delivery Systems - Targeted approach to disease management would be dealt with in Part III of this series.
A target oriented DDS by definition - supplies drug selectively to its site(s) of action(s) in a manner that provides maximum therapeutic activity (though controlled and predetermined drug release kinetics), presents degradation or inactivation during transit to the target sites and protects the body from adverse reactions because of inappropriate disposition.
For drugs that have a low therapeutic index, targeted drug delivery proves an effective treatment at a relatively low drug concentration.
There are several other reasons/ benefits cited for site-specific delivery . For inquiries contact Shruti.
CLASSIFICATION OF DRUG TARGETING:
Drug targeting has been classified into three types:
(a) First-order targeting --- this describes delivery to a discrete organ or tissue;
(b) second-order targeting----this represents targeting to a specific cell type(s) within a tissue or organ (e.g. tumor cells versus normal cells and hepatocytic cells versus Kupffer cells);
c) third-order targeting ---- this implies delivery to a specific intracellular compartment in the target cells (e.g. lyososomes).
Basically, there are three approaches for drug targeting. The first approach involves the use of biologically active agents that are both potent and selective to a particular site in the body (magic bullet approach of Ehrlich). The second approach involves the preparation of pharmacologically inert form of active drugs that when they reach the active sites become activated by a chemical or enzymatic reaction (prodrug approach). The third approach utilizes a biologically inert macromolecular carrier system that directs a drug to a specific site in the body where it is accumulated and affects its response (magic gun or missile approach).
Regardless of the approach, the therapeutic efficacy of target drug delivery systems depends on the timely availability of the drug in active form at the target site(s) and its intrinsic pharmacological activity. The intrinsic pharmacokinetic properties of the free drug should be the same, irrespective of whether or not it is introduced into the body attached to a carrier. A drug can selectively access to, and interact with, its pharmacological receptors, either passively or by active processes. Passive processes rely on the normal distribution pattern of a drug-drug-carrier system, whereas the active routes use cell receptor-recognizing ligand(s) or antibodies (“homing” or “vector” devices) to access specific cells, tissues, or organs in the body.