Benzocaine has been associated with a rare, but serious, condition called methemoglobinemia, which reduces the amount of oxygen carried in the bloodstream and can result in death in the most severe cases.
Patients who develop methemoglobinemia may experience pale, gray or blue colored skin, lips and nail beds; headache; lightheadedness; shortness of breath; fatigue and rapid heart rate. In some cases, symptoms of methemoglobinemia may not always be evident or attributed to the condition. The signs and symptoms usually appear within minutes to hours of using benzocaine. Conditions such as anemia, heart disease and lung disease may exacerbate the toxicity of methemoglobinemia. Report side effects or medication errors from the use of benzocaine to the FDA MedWatch program, call 1-800-332-1088 or fax 1-800-FDA-0178.