Severe Methemoglobinemia Linked to Gel-Type Topical Benzocaine Use: A Case Report

Background: Methemoglobinemia is an uncommon cause of tissue hypoxia, but it can be life threatening if it is not identified and treated promptly. Objectives: To highlight the importance of understanding the potential risks of over-the-counter medications, especially in unsupervised use. Topical benzocaine must be used with caution, even in the healthy population. Case report: We report a case of methemoglobinemia secondary to topical benzocaine gel. A 6-year-old boy presented to our Pediatric Emergency Department with cyanosis, vomiting, and lethargy after using a gel-type, 7.5% benzocaine (Baby Orajel®) for a toothache. Physical examination revealed dusky blue skin, tachycardia, tachypnea, and a normal neurologic examination. His percutaneous oxygen saturation remained 77–83% despite the administration of 100% oxygen. His arterial blood sample had a dark chocolate color appearance, and methemoglobinemia was suspected. His methemoglobin level was 69.9%, which is considered a lethal level. After a single dose of methylene blue (1 mg/kg/dose), cyanosis was reduced and oxygenation improved. Conclusion: Over-the-counter topical benzocaine should be used with caution, and the presence of methemoglobinemia must be promptly identified and treated.