Slippery, hydrophilic coating compositions of a polyurethane/urea prepolymer adduct intermediate commingled with at least one dissimilar hydrogel polymer precursor, and materials composed of a polymeric plastic or rubber substrate or a metallic substrate with a slippery hydrogel coating of a polyurethane/urea prepolymer adduct intermediate and at least one dissimilar hydrogel thereon, such that the coating composition tenaciously adheres to the substrate, are disclosed. The coating compositions and coated materials are non-toxic and biocompatible, and are ideally suited for use on medical devices, particularly, catheters, catheter balloons and stents. The coating compositions, coated materials and coated devices demonstrate low coefficients of friction in contact with body fluids, especially blood, as well as a high degree of wear permanence over prolonged use of the device. The hydrogel coatings are capable of being dried to facilitate storage of the devices to which they have been applied, and can be instantly reactivated for later use by exposure to water.