Methemoglobinemia is a side effect of Dapsone (4, 4 diaminodiphenylsulfone or DDS) observed following therapeutic dose administration or after an accidental overdose incidentally with hemolysis causing suffering hypoxic. About an observation, we recall the main clinical, toxicological and therapeutic characteristics of overdose with Dapsone.

An elderly man of 30 years, without significant medical history, was hospitalized in the department of dermatology for extensive bullous dermatosis. The patient was treated orally with 2mg/kg daily (150mg per day) of DDS. Accidentally, he took 450mg, 3 times per day for 5 days. On the sixth day, the patient presented a mucocutaneous pallor, cyanosis of the extremities and lips and tachycardia of 160 beat / min. The dosage of methemoglobinemia by spectrophotometry objectified a value of 26%. Medical decision was to stop the DDS and put the patient on oxygen therapy and in vitamin C orally with 3 g per day. Methemoglobinemia analysis performed 2 days after was 19% with regression of clinical signs. Regular monitoring of methemoglobinemia showed degression values ranging from 11.8% to 3.3% at tenth day after accidental overdose. The outcome was favorable and the patient was supported in dermatological consultation.

Methemoglobinemia is an expected side effect of Dapsone. Its reduction by the methylene blue is indicated for levels above 30% or when it is poorly tolerated. Its evolution is extended due to the long half- life of the toxicant.