Benzocaine-induced methemoglobinemia: experience from a high-volume transesophageal echocardiography laboratory

J Am Soc Echocardiogr. 2003 Feb;16(2):170-5. doi: 10.1067/mje.2003.5.


Benzocaine (ethyl aminobenzoate), a topical anesthetic widely used before transesophageal echocardiography, has been reported to cause acquired methemoglobinemia. The incidence of benzocaine-induced methemoglobinemia in clinical practice, however, has been difficult to estimate. After systematic review of our institutional experience for clinically recognized cases of benzocaine-induced methemoglobinemia in patients undergoing transesophageal echocardiography, we report an estimated incidence of 0.115% (95% confidence interval 0.037-0.269). This report also provides the largest analysis of the incidence of methemoglobinemia in readministration cases. Although controversy remains as to whether this is an idiosyncratic versus dose-related response, a description of purported patient risk factors is included.

MeSH terms

  • Adult
  • Aged
  • Benzocaine / adverse effects
  • Echocardiography, Transesophageal*
  • Female
  • Humans
  • Incidence
  • Male
  • Methemoglobinemia / chemically induced
  • Methemoglobinemia / diagnostic imaging
  • Methemoglobinemia / epidemiology*
  • Middle Aged
  • Retrospective Studies
  • Risk Factors


  • Benzocaine