In a further reaction, ClO − and H 2 O 2 can produce the release of singlet-O 2 and thereby amplify the cytotoxic potential. It has been generally agreed that part of the anti-inflammatory activity of dapsone results from a (reversible) inhibition of MPO. This leads to an inhibition of the conversion of H 2 O 2 to HOCL. Early works on the mechanisms of action had already postulated a direct inhibition of MPO by dapsone [ 144 , 161 ]. Subsequent studies have confirmed the inhibitory effect of dapsone on MPO [ 19 , 88 , 92 , 93 , 157 ]. It is assumed that dapsone exerts a direct inhibition of MPO which leads to the formation of inactive intermediates of the enzyme. As hypochlorous acid is an integral part not only of the antibacterial/antiprotozoal armamentarium of PMN and eosinophils but can also cause tissue damage in non-infectious disease states [ 163 ], the inhibition of MPO by dapsone might account for the anti-inflammatory potential of the sulfone.