Acquired methemoglobinemia: a retrospective series of 138 cases at 2 teaching hospitals

Medicine (Baltimore). 2004 Sep;83(5):265-273. doi: 10.1097/


Methemoglobin is a form of hemoglobin that does not bind oxygen. When its concentration is elevated in red blood cells, functional anemia and tissue hypoxia may occur. We performed a retrospective case series to describe the cases of acquired methemoglobinemia (methemoglobin level >2%) detected and the clinical circumstances under which they occurred at 2 tertiary care hospitals and affiliated outpatient clinics over 28 months. We surveyed co-oximetry laboratory data to identify patients with methemoglobinemia. We reviewed these patients' medical records to extract the clinical information and context. One hundred thirty-eight cases of acquired methemoglobinemia were detected over the 28 months. There was no gender predisposition, and the condition occurred over a wide range of ages (patients aged 4 days to 86 years). Cases occurred in many areas of the hospital, including outpatient clinics. One fatality and 3 near-fatalities were directly attributable to methemoglobinemia. Dapsone was the most common etiology of acquired methemoglobinemia, accounting for 42% of all cases. The mean peak methemoglobin level among these individuals was 7.6%. In 5 of the patients with the most severely elevated levels, 20% benzocaine spray (Hurricaine Topical Anesthetic spray, Beutlich Pharmaceuticals, Waukegan, IL) was the etiology, associated with a mean peak methemoglobin level of 43.8%. Eleven pediatric patients developed methemoglobinemia either from exogenous exposure, such as drugs, or due to serious illness, such as gastrointestinal infections with dehydration. Almost all (94%) patients with methemoglobinemia were anemic. Drugs that cause acquired methemoglobinemia are ubiquitous in both the hospital and the outpatient setting. Acquired methemoglobinemia is a treatable condition that causes significant morbidity and even mortality. We hope that a heightened awareness of methemoglobinemia will result in improved recognition and treatment. Primary prevention efforts have the potential to reduce the morbidity and mortality associated with this condition.

Publication types

  • Case Reports
  • Comparative Study

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Anti-Inflammatory Agents, Non-Steroidal / administration & dosage
  • Anti-Inflammatory Agents, Non-Steroidal / adverse effects
  • Biomarkers / blood
  • Child
  • Child, Preschool
  • Dapsone / administration & dosage
  • Dapsone / adverse effects
  • Female
  • Glucosephosphate Dehydrogenase Deficiency / complications
  • Glucosephosphate Dehydrogenase Deficiency / metabolism
  • Hospitals, Teaching
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Maryland / epidemiology
  • Methemoglobin / metabolism
  • Methemoglobinemia / diagnosis*
  • Methemoglobinemia / etiology
  • Methemoglobinemia / metabolism
  • Middle Aged
  • Multicenter Studies as Topic
  • Oximetry
  • Retrospective Studies


  • Anti-Inflammatory Agents, Non-Steroidal
  • Biomarkers
  • Dapsone
  • Methemoglobin