They are classified in two different categories Topo I inhibitors or interfacial Topo I poison, which inhibit the rotation of the axis or the religation of the enzymatic reaction and then stabilize the covalent complexes of Topo DNA 70; Topo II inhibitors or catalytic Topo inhibitors act by blocking two essential steps in the enzymatic catalytic cycle ligation to the substrate or cleavage complex during the formation of the covalent bond lasix common side effects