Earlier this month, the US Food and Drug Administration warned the public about a rare blood disorder associated with benzocaine, available widely in over-the-counter (OTC) local anesthetic sprays, gels, creams and liquids. Local anesthetics numb pain when applied to the skin or mucous membranes. The FDA advisory has implications for health professionals and consumers alike, especially parents of children less than two years of age since the disorder occurs disproportionally in babies.
The disorder, known as methemoglobinemia (pronunciation here), reduces the ability of blood to carry oxygen into body tissues. In the most severe cases, it can result in death. The FDA advisory noted that people who develop methemoglobinemia may experience pale, gray or blue colored skin, lips, and nail beds; shortness of breath; fatigue; confusion; headache; lightheadedness; and rapid heart rate. Symptoms usually appear within minutes to one or two hours after using benzocaine gels or liquids.
In a review of data from FDA’s adverse event reporting system, FDA discovered that cases occurred mainly in children aged two years or younger who were treated with benzocaine gel for teething. This is probably related to the fact that detoxifying enzyme systems in infants aren’t fully developed. The Agency said they are particularly concerned about the use of OTC benzocaine products in this age group because of the difficulty that parents may have in recognizing the signs and symptoms of methemoglobinemia when using these products at home. Symptoms of methemoglobinemia may not always be evident or attributed to the condition.
Our Institute began warning about methemoglobinemia from local anesthetics nearly 15 years ago and we published a specific warning about benzocaine in 2002. Subsequently, we published a review of 132 cases we identified in FDA’s adverse event reporting system database, including 107 serious adverse events and 2 deaths.
In 123 of the cases we studied, the product was a spray; in two cases, a benzocaine-containing lozenge, and one case, a gel. Our initial hypothesis was that most cases would be linked to accidental overdoses of spray applied to mucosal tissues. However, this was not supported by the available data. Although we identified 14 cases that may have involved an overdose, in 37 other cases the dose was listed as a single spray of unspecified duration. In the 69 cases that specified a dose, 37 indicated that only a single spray was applied (approximately the recommended amount). Development of the condition was unpredictable and there did not appear to be any correlation with the amount of benzocaine the patient received. Methemoglobinemia can also occur after the first time a person uses benzocaine, or after using a benzocaine product multiple times.
FDA said that products like Anbesol and Baby Orajel should no longer be used for babies under two “except under the advice and supervision of a physician. However, the unpredictability of cases makes me think it shouldn’t be used at all in babies. After all, why even take any chance when safer alternatives are available..
Although it wasn’t mentioned in the FDA advisory, I’d also advise caution against using benzocaine on highly inflamed or denuded skin because the drug can be absorbed and there have been very rare cases of methemoglobinemia when benzocaine iis used n such situations. Cases have also occurred in adults as well as children. One child even developed methemoglobinemia after benzocaine was used in a suppository. Dogs have developed it when it was applied to skin lesions.
Since there are several benzocaine products on the market for treating infants with teething pain, it’s important for parents to be aware of them and always read the “Drug Facts” label or asking a pharmacist for help when selecting products. Benzocaine is available as prescription only or over the counter in a wide variety of products, such as lozenges for sore throat, gels for toothache, sprays for minor burns or sunburn, solutions for earaches, and suppositories for relief of hemorrhoidal symptoms. By brand name, products include Americaine, Anbesol, Boil Ease, Cepacol Sore Throat, Cetacaine, Dermoplast, Exactacain, Hurricaine, Lanacane, Orabase with Benzocaine and Orajel. These contain benzocaine in amounts up to 20%. A table listing all the OTC products can be seen here.
Benzocaine is very commonly used in hospitals and diagnostic areas, most often used as a spray to numb the back of your throat to stop the gag reflex when inserting diagnostic instruments. This helps doctors view structures in your gastrointestinal system or breathing tubes. It also makes the procedure less complicated for the physician and more easily tolerated by the patient. Some of the cases in our study did occur under these circumstances and some hospitals, including those within the Department of Veterans Affairs, stopped using benzocaine in 2006.