Abstract: Improved active agent systems with novel carriers as membrane, release, and coating polymers for said active agents; the polymers are water absorptive polyurethane polymers prepared from resins having a low ratio of carbon to oxygen to nitrogen or having ionic, quaternary ammonium or salt groups in the resin backbone and a low amount of isocyanate; the water absorptivity of the polyurethane polymers is above 10%, preferably above 20%, and these polymers may range to completely gel-like, high water absorbtive polymers; these active agent polymers are useful as in medicinal, insecticidal, pesticidal, algaecidal, etc. applications; as well as zero release agents, body implants and coatings requiring hydrophilic properties; other use for the active agent systems are in sensing membranes or coatings or ion transport recognition devices such as in gaseous or liquid media; as a hydrogel providing a leachable matrix wherein the leaching agent may be body fluids, e. g., animals or human, e. g.