Fate of water-soluble polymers administered via different routes

The biological fate of synthetic water-soluble polymers administered to mice by injection at different sites is described. After intraperitoneal (ip), subcutaneous (sc), and intramuscular (im) injections of 125I-labeled poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) with various molecular weights, the time-course of polymer concentration in the blood was measured and analyzed pharmacokinetically. The location of PVA in the body was similar to that of PEG; that is, the elimination from the injection sites and the translocation from the injection sites into the blood circulation were similar for both polymers. The elimination rate of both polymers from the injection sites increased in the order ip > sc > im. After sc and im injections of polymers, the elimination rate decreased with an increase in the molecular weight, whereas the elimination rate of polymers injected showed no molecular weight dependence over the range studied, regardless of the type of polymers used. The time-course of polymer concentration in the blood depended largely on the injection route of the polymers, and the polymer elimination from the blood circulation was enhanced with the decreasing molecular weight of polymers injected. It was concluded that the molecular weight and the injection site are the important factors that affect the concentration profile of polymers in the blood circulation.