A century of the synthesis of dapsone: its anti-infective capacity now andthen

Background Although dapsone was first synthesized in 1908, a quarter of a c entury was to pass before it was used in the treatment of bacterial infecti ons. Dapsone was, however, too toxic for humans (because of the excess dosa ge which was administered at that time) and was thus considered to be of no value in the treatment of common bacterial infections. Since the early 195 0s, dapsone has been recognized as being uniquely effective against a numbe r of noninfectious, inflammatory diseases and, today, this is its main indi cation. Thus, the reason why dapsone was first introduced into medicine, na mely the treatment of bacterial infections, has been set aside and its main current applications are the treatment of noninfectious, inflammatory, aut oimmune, and bullous diseases. Objective To study the anti-infective capacity of dapsone against common ba cterial infections. As many patients who receive dapsone for the treatment of noninfectious, inflammatory diseases have a concomitant bacterial infect ion or a superinfection of their skin disease, we thought that, if dapsone proved to be effective against common bacterial infections, it may obviate the need for an additional antimicrobial drug in these patients. Methods Three bacterial ATCC > strains (Streptococcus pyogenes, Staphylococ cus aureus, and Escherichia coli) were tested by a macrodilution minimal in hibitory concentration (MIC) test for dapsone. Dapsone concentrations were between 0.06 and 1125 mug/mL. Results Even the highest concentration of dapsone of 1125 mug/mL did not in hibit bacterial growth. Conclusions Our results indicate that dapsone has no antibacterial effects whatsoever. Even at very high concentrations, it does not suppress the grow th of most susceptible strains of bacteria. The story of dapsone (i.e. the long time that elapsed between its synthesis to its use for the chemotherap y of infectious diseases) will not repeat itself this time.