Abstract: A polymer of formula (I) where X1 and X2 respectively represent the alpha and omega end groups of the polymer; R1 represents a hydrogen atom or a straight or branched chain alkyl group; R2 represents a straight or branched chain alkyl group which is substituted by a group which may have a positive charge at physiological pH; and n represents the number of repetitive units of the polymer, or a copolymer thereof; for use as a medicament and for treatment of a heparin overdose wherein the polymer of formula (I) has been found to have a selectivity and affinity for heparin.