A therapeutic composition is provided including a polysaccharide or a cationic peptide dissolved in an organic substance. The polysaccharide can be heparin or a derivative of heparin. The cationic peptide can be L-arginine, oligo-L-arginine or poly-L-arginine. The organic substance can be formamide. A method of coating an implantable medical device is also provided, comprising applying the therapeutic composition to the device and allowing the organic substance to evaporate. The device can be a stent.