Ferric Carboxymaltose-mediated Methemoglobinemia

Abstract

Background: Methemoglobinemia is a life-threatening disorder, with levels above 1 percent considered abnormal and typically resulting from drug or toxic substance exposure. Case Presentation: In this study, we describe a case of a 43-year-old woman with a long-standing complaint of fatigue. Iron deficiency anemia was diagnosed based on the blood test findings of hemoglobin of 101 g/L, mean red blood cell volume of 75 fL, ferritin of 2.81 ug/L, transferrin saturation of 4.3 percent, and C-reactive protein of 0.6 mg/L. As a preferred treatment option, 1000 mg ferric carboxymaltose on two distinct days was preferred. After administering the first dose of the medication, we noticed incidentally that methemoglobin levels increased to 2.3%. When venous blood gas was repeated before and after administration of the second dose of the drug, methemoglobin levels were found to be 0.8% and 1.8%, respectively. There was no change in vital signs in both two dosages, and she only suffered a temporary sore throat. Her anemia improved with intravenous iron therapy, and she is currently being followed in our clinic. Discussion: No case or research reporting an increase in methemoglobin levels following oral and/or intravenous treatment to patients with iron deficiency anemia has been found in the literature. Therefore, this is the first contribution to the existing literature.