Background: Benzocaine is a local anesthetic found in over the counter (OTC) topical medications. Unintentional exposures to these products are common in children; however, the development of symptoms after such exposures is rare, as is severe methemoglobinemia (MHb). When MHb does occur, treatment with methylene blue (MB) is not usually required. We report 2 cases of accidental ingestions of benzocaine-containing products producing MHb requiring MB.
Case 1: A 22 month-old girl presented to the Emergency Department (ED) with cyanosis. Pulse oximeter (SpO 2 ) read 85-86% despite 100% supplemental oxygen (O 2 ) via a non-rebreather facemask. Vital signs were notable for a heart rate of 182 bpm. She was awake and alert with peri-oral, oral, and peripheral cyanosis but had no Objective findings of respiratory distress. Her blood on venipuncture was dark brown. She had received Nyquil R the previous evening but had no other known medication exposures. She received 1 mg/kg of MB via an intraosseous line with resolution of her cyanosis and improvement in her SpO 2 within 10 min. Her MHb level returned at 50.9% (normal: 1.5%). She was transferred to a pediatric hospital, received an additional 1 mg/kg of MB for a repeat MHb level 11.6%, and was discharged home the following day. An exposure to Vagisil R was determined to be responsible for her symptoms.
Case 2: A 4 year-old boy with a history of asthma and chronic sinusitis presented to the ED with diffuse cyanosis after the ingestion of Orajel(TM). He was behaving normally but his SpO 2 was in the mid 80s on room air; this improved to 91% on 15 L of high flow O 2. His respiratory rate, lung examination, and chest X-ray were normal. Prescribed medications included azithromycin, levocetirizine, budesonide, and albuterol. His MHb level was 31%. After admission to the Pediatric ICU, his SpO 2 dropped to the 60s. He then received MB 1mg/kg IV, and within 20 minutes his cyanosis resolved and his SpO 2 normalized. He was observed overnight and discharged home the next day.
Discussion: Despite wide availability of a significant number of OTC medications containing benzocaine, unintentional pediatric exposures necessitating MB are rare as the anesthetic effects of benzocaine usually limit the amount ingested. Most case reports link the development of MHb to the use of benzocaine in oral and endoscopic procedures. These 2 cases highlight the potential for MHb to occur in unintentional pediatric ingestions and the importance of history, clinical examination, and physical assessment in making the diagnosis.
Conclusion: Methemoglobinemia requiring treatment with methylene blue may occur after unintentional pediatric ingestions of over the counter products containing benzocaine.