Modified-Release Drug Delivery Systems: Site-Targeted

Site-targeted drug delivery systems enhance therapeutic efficacy while reducing side effects and treatment costs associated with conventional approaches.

These systems can be categorized into four orders of targeting. First-order systems passively direct drugs to the capillary bed of organs or tissues, while second-order systems target specific cells, such as tumor cells.

Third-order systems facilitate intracellular drug delivery, while fourth-order systems target macromolecules.

Additionally, passive targeting relies on the carrier system’s physicochemical properties. In contrast, active targeting employs ligands or monoclonal antibodies to improve drug specificity.

Drug carriers protect drugs, improve uptake, and reduce clearance through covalent or non-covalent bonding.

Polymeric carriers typically comprise a polymeric backbone, a targeting ligand, a solubilizer, and a spacer that covalently links the drug.

Other carriers include albumin, which prolongs drug action; lipoproteins, which support intracellular drug transport; and liposomes, which improve efficacy and reduce side effects.