Advisory on Benzocaine Sprays and Methemoglobinemia
FDA Patient Safety News: Show #50, April 2006

FDA recently issued a Public Health Advisory to remind health care professionals that the overuse of benzocaine anesthetic sprays can cause methemoglobinemia, a potentially life-threatening condition that can result in cyanosis, confusion, hemodynamic instability and coma.

Benzocaine sprays, including those sold under the brand names Hurricaine, Topex and Cetacaine, are used to anesthetize the mucous membranes of the mouth and throat when preparing patients for minor surgery, endoscopic procedures and endotracheal intubation. Methemoglobinemia is a known side-effect when benzocaine sprays are used, but the risk can increase when practitioners use multiple sprays or sprays of longer duration than recommended.

FDA is reviewing the safety data for these products to determine if additional action is needed. FDA recommends the following actions to help minimize the risk:

• Use only the minimum amount of benzocaine spray to produce the required anesthetic effect.

• Carefully observe patients treated with benzocaine sprays for signs of methemoglobinemia. These include headache, lightheadedness, shortness of breath, anxiety, fatigue, pale, gray or blue colored skin, and tachycardia. Blood that's chocolate-brown in color is a late sign of life- threatening levels of methemoglobinemia.

• Promptly treat patients suspected of having high levels of methemoglobin. Supplemental oxygen alone is not effective. The only known treatment is intravenous administration of methylene blue.

• Do not rely on commonly available 2-wavelength pulse oximetry to detect hypoxia because it may be unreliable in cases of methemoglobinemia. Analyze blood samples with a co-oximeter instead.

• Infants less than 4 months of age and patients with certain hemoglobin and enzyme abnormalities are at increased risk for developing toxic levels of methemoglobin. Patients who have breathing problems such as asthma, bronchitis, or emphysema, patients with heart disease, and patients who smoke are at greater risk for complications related to methemoglobinemia. All of these patients would likely benefit from either the use of topical anesthetics that do not contain benzocaine or other forms of therapy.

Additional Information:

FDA MedWatch Safety Alert 2006 - Benzocaine Sprays. February 13, 2006.
http://www.fda.gov/medwatch/safety/2006/safety06.htm#benzocaine