Dapsone intoxication can be a life-threatening condition due its enterohepatic recirculation pharmacokinetics, and therefore, persistent methemoglobinemia development. We describe a case of a 17-year-old girl who was admitted 4 h after ingesting 5 g of dapsone. She presented methemoglobinemia (39%) and showed clinical signs of toxicity (cyanosis and altered mental status) despite mechanical ventilation. Multiple activated charcoal dosis and methylene blue infusions were performed. Notwithstanding initial improvement, a pattern of peaks and valleys was observed in serial methemoglobinemia measurements, with cyclic states of hypoxemia. On account of enterohepatic recirculation pharmacokinetics, clearance was enhanced by whole bowel irrigation. After 7 days of hospitalization, she was discharged in good general condition.