The possible inhibition of lysosomal enzymes by dapsone (diaminodiphenylsulfone) was studied. Experimentally induced hypervitaminosis A in rabbits results in loss of chondroitin sulfate from cartilage matrix through the release of lysosomal enzymes.
In this study, thinning and decreased toluidine blue and Alcian blue staining of tracheal and articular cartilage produced by the administration of 500,000 international units of vitamin A daily were inhibited by the administration of dapsone. These findings strongly suggest that dapsone inhibits lysosomal enzyme activity. Inhibition of lysosomal enzyme activity may play a role in the therapeutic effects of dapsone on certain diseases such as dermatitis herpetiformis.