Extracorporeal hemoperfusion through polyacrolein microsphere beads (APAMB) attached to antidigoxin antibodies is an effective treatment of digitalis intoxication. In order to increase the binding capacity of the APAMB columns the active sites of the antidigoxin antibodies were protected by ouabain during the binding to the microbeads. This brought about an 11-18 percent increase in digoxin binding capacity of the columns. It was also found that binding capacity does not increase with the rise of antibody concentration beyond a certain limit. Protection of antibody binding sites and determination of optimal concentration are, therefore necessary steps during preparation of antibody based hemoperfusion columns.