Methemoglobinemia secondary to over-the-counter Anbesol

BackgroundMethemoglobinemia is a potentially lethal condition which may result from exposure to benzocaine. It must be treated promptly, because it may cause a significant decrease in oxygen delivery to tissues and organs.Case descriptionA 39-year-old caucasian man presented to the emergency department (ED) with dental pain. After a review of systems and a dental exam, an oxygen saturation of 90% was noted. The patient reported no previous cardiac or pulmonary pathology, but did report using a large amount of over-the-counter Anbesol. A second oxygen saturation measurement had fallen to 87%. An arterial blood gas sample was taken, and the patient was found to have high levels of methemoglobin. He was transfered to the critical care ED and treated with 2 mg/kg intravenous methylene blue.Clinical implicationsDentists must be aware of the possible lethal effects of benzocaine toxicity, including methemoglobinemia. It is important to recognize the signs and symptoms and act in a judicious manner.