schiff base which is hydrolytically unstable and can release the amine containing drug under in vivo conditions scheme 4 shows an alternative strategy for forming the prodrug by the reaction of the amino group of heparin nh 2 with a keto group on the drug molecule to form an imine schiff base linkage in still some other embodiments the prodrug described herein can be formed via an acetal or hemi acetal by heparin cho with a hydroxyl group or hydroxyl groups on a drug scheme 5 or vice versa scheme 6 the acetal or hemi acetal can undergo hydrolysis under in vivo conditions to release the drug as shown in scheme 5 the aldehyde group of heparin cho can react with the hydroxyl group or groups on a drug to form a prodrug with an acetal linkage or hemi acetal linkage scheme 5 alternatively the hydroxyl group or groups can react with an aldehyde or keto group on a drug to form a prodrug with an acetal linkage or hemi acetal linkage scheme 6 in one embodiment the hydroxyl group on the c40 position of everolimus can react with the carboxyl group on heparin to form an ester bond so as to form an everolimus heparin prodrug in another embodiment a drug can form a prodrug with heparin attached to a polymer such as poly l lysine g ethylene glycol pll peg which can be pll g peg or pll co peg in this embodiment the amino group in the pll peg can react with a carboxyl group in heparin to form an amide bond.