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.

OBJECTIVE

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.

METHODS

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.

CONCLUSIONS

Over-the-counter topical benzocaine should be used with caution, and the presence of methemoglobinemia must be promptly identified and treated.