A Rare Culprit of Methemoglobinemia

Abstract

Methemoglobinemia is a rare cause of hypoxia and can be a diagnostic challenge early in the disease course. The incidence of medication-induced methemoglobinemia is more common than congenital-related methemoglobinemia. The most common cause of methemoglobinemia is exposure to household detergents, illicit drugs, or medications with nitrate or sulfonamide chemical groups. The 2 main medications accounting for up to 45% of medication-induced cases are dapsone and benzocaine. We report a case of hypoxia and diarrhea with an arterial blood gas (ABG) showing methemoglobinemia at 26%. Infectious and autoimmune workup were negative. Methemoglobinemia level returned to normal level within 2 weeks of hydrochlorothiazide discontinuation, suggesting medication-induced methemoglobinemia at appropriate hypertension dosage. In this case, there was an acute rise in methemoglobin levels following initiation of an hydrochlorothiazide-losartan combination, which improved following the discontinuation of hydrochlorothiazide. Extensive workup ruled out cytochrome b5 reductase (Cb5R) and Glucose-6-phosphate dehydrogenase (G6PD) deficiency, which raised the suspicion of hydrochlorothiazide-induced methemoglobinemia, as it is part of the sulfa drug family.

Occult methemoglobinemia in a medically-complex child and the opportunity for pharmacist intervention in the pediatric population

“…The risk of developing methemoglobinemia with benzocaine use is well-established in the medical literature. [2][3][4][5][6][7][8] Speci c predisposing factors for this condition include G6PD de ciency as well as low cytochrome-b5 reductase (Cyb5R) activity, which is common in infants, especially those born premature, and heterozygotes for pathogenic variants of this enzyme. 11 Under normal conditions, the Cyb5R pathway is the main appreciable mechanism in the body for elimination of methemoglobin.…”