Risk factors for serious methemoglobinemia following exposure to benzocaine:
(1) use in children less than 2 years of age (typically used for teething pain)
(2) failure to follow instructions for use
(3) excessive application to mucous membranes of the mouth or throat
(4) use of a product with a high concentration of benzocaine
(5) failure to see a healthcare provider after the clinical onset of methemoglobinemia
(6) continued use of benzocaine preparation after onset of methemoglobinemia
(7) accidental ingestion by a child when the preparation was accessible
(8) inborn error of metabolism such as glucose 6-phosphate dehydrogenase (G6PD) deficiency, NADH-methemoglobin reductase deficiency, pyruvate kinase deficiency, etc.
(9) comorbid pulmonary disorders such as asthma or bronchitis
(10) concurrent exposure to nitrites, nitrates or other compounds capable of causing methemoglobinemia
Clinical findings of the methemoglobinemia may include:
(1) pale, gray or bluish skin within minutes to hours of benzocaine use
(2) dyspnea
(3) fatigue
(4) confusion, headache or lightheadedness
(5) tachycardia
