Methemoglobinemia from overdose of phenazopyridine hydrochloride.

A case of severe methemoglobinemia and hemolytic anemia following ingestion of 5.6 gm of phenazopyridine with suicidal intent by a 16-year-old woman was successfully treated with intravenous methylene blue. Methemoglobinemia was suspected in this patient because of her intense central cyanosis, chocolate-colored blood, and minimal dyspnea. The patient's peripheral blood smear exhibited "bite cells." To the best of our knowledge, this is only the third such case reported in the literature. The pathophysiology, diagnosis, and therapy are reviewed.