Goal of targeting drugs to specific sites in the body, where the pharmacological action is desired and sparing other tissues has been actively pursued all these years. Currently the problems associated with systemic drug administration are: the lack of drug specific affinity toward a pathological site; even biodistribution of pharmaceuticals throughout the body; non-specific toxicity and other adverse side-effects due to high drug doses. The increased concentration of a drug in the site of disease made possible by targeted delivery can be used to increase efficacy, reduce side effects, or achieve some of both. Drug targeting, i.e. predominant drug accumulation in the target zone independently on the method and route of drug administration, may resolve many of these problems. Currently, the principal schemes of drug targeting include direct application of a drug into the affected zone, passive drug targeting (spontaneous drug accumulation in the areas with leaky vasculature, or Enhanced Permeability and Retention-EPR-effect), ‘physical’ targeting (based on abnormal pH value and/or temperature in the pathological zone), magnetic targeting (or targeting of a drug immobilized on paramagnetic materials under the action of an external magnetic field), and targeting using a specific ‘vector’ molecules (ligands having an increased affinity toward the area of interest). The last approach provides the widest opportunities. Various pharmaceutical carriers as soluble polymers, microcapsules, microparticles, cells, cell ghosts, liposomes, and micelles have been successfully used for targeted drug delivery in vivo. In this article we are concerning mainly on active targeting which include manipulation or modification of drug carrier so that it easily approaches the particular biosite.
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