Hexadimethrine bromide (commercial brand name Polybrene) is a cationic polymer used to increase the efficiency of transduction of certain cells with a virus in cell culture. Hexadimethrine bromide acts by neutralizing the charge repulsion between virions and sialic acid on the cell surface. It has other uses, including a role in protein sequencing. Historically, hexadimethrine bromide was sometimes used to reverse heparin anticoagulation during open-heart surgery. Its use has been supplanted by protamine sulfate.