Abstract
Passive targeting strategies utilizing macromolecular drug carriers were reviewed from the viewpoint of pharznacokinetics. Although active targeting using target-specific carriers is a very attractive approach, successful results are limited. A variety of problems should be overcome to achieve not only active targeting but also passive targeting. Pharmacokinetic analysis based on a clearance concept has demonstrated that in vivo behavior of macromolecules after systemic injection depends on their physicochemical properties such as molecular weight and electric charge. Based on the findings, passive targeting systems for antitumor agents were developed. Prolonged retention of protein drugs in the blood circulation was also possible by chemical modification with macromolecular carriers including polyethylene glycol. The success in passive targeting approach will facilitate the development of active drug targeting systems.
