2013 Volume 52 Issue 15 Pages 1741-1743
We herein report a case of methemoglobinemia induced by trimethoprim-sulfamethoxazole (TMP/SMX). A 41-year-old woman with systemic lupus erythematosus (SLE) received TMP/SMX for prophylaxis of pneumocystis pneumonia (PCP) on the 7th day of hospitalization. She suddenly developed dyspnea and cyanosis on the 9th day of hospitalization. The level of oxygen saturation (SaO2) decreased, and the concentration of methemoglobin (MetHb) in the blood was elevated. We diagnosed the patient with methemoglobinemia induced by TMP/SMX. Methemoglobinemia should be considered in cases of sudden dyspnea following TMP/SMX administration.