The present technology provide compositions that are drug delivery systems for the sustained release of anti-stenotic drugs for the treatment and prevention of occlusion of blood vessels, particularly after perivascular surgery. The compositions include a hydrogel, unimolecular micelles dispersed within the hydrogel, and an effective amount of anti-stenotic drug dispersed within the unimolecular micelle. The hydrogel may be a di-or tri-block copolymer comprising one block of poly(ethylene glycol) (PEG) and one or two blocks of poly(lactic-co-glycolic acid) (PLGA). The unimolecular micelle may include three domains: a dendritic polymer core, hydrophobic block polymers (e.g., PVL, PVCL, and/or PCL) attached to the core and PEG attached to the hydrophobic block polymers.