 Fondaparinux is a synthetic pentasaccharide factor Xa inhibitor.Fondaparinux binds antithrombin and accelerates its inhibition of factor Xa.Apart from the O-methyl group at the reducing end of the molecule, the identity and sequence of the five monomeric sugar units contained in fondaparinux is identical to a sequence of five monomeric sugar units that can be isolated after either chemical or enzymatic cleavage of the polymeric glycosaminoglycans heparin and heparan sulfate (HS).