A physician administered three sprays of benzocaine 20% (Hurricaine), 1 to 2 seconds each, to numb a patient's throat before placing a nasogastric tube. About an hour later, the patient became hypoxic. When he received oxygen but didn't improve, arterial blood gases were drawn and the blood had a muddy brown appearance. A methemoglobin level was done and the result was 46% (normal range, 0 to 3%). The patient received methylene blue, which decreases methemoglobin by accelerating enzymatic reduction, and within 2 hours his methemoglobin level was 0.9%.
Sprays that contain benzocaine are known to cause methemoglobinemia, which can lead to life-threatening complications such as myocardial infarction and death. The risk increases when the number and duration of sprays administered exceed the package guidelines. The package insert states that the dosage should be a 1/2-second spray, which may be repeated once.
Benzocaine spray poses a greater risk to patients who may be predisposed to methemoglobinemia, including infants under age 6 months and older adults with cardiac problems. Alternatives to benzocaine 20% topical for oral or mucosal application include lidocaine jelly 2% or lidocaine 4% preservative-free ampules for use with an atomization device.