Benzocaine sprays are used for locally numbing mucous membranes of the mouth and throat during minor surgical procedures or when a tube must be inserted into the stomach or airways.
The sprays are known to be occasionally associated with methemoglobinemia. However, cases of methemoglobinemia have also occurred after errors due to incorrect use of benzocaine sprays (e.g., longer duration or excessive sprays.)
Methemoglobinemia occurs when too much of the hemoglobin in red blood cells becomes unable to bind and carry oxygen. Until the condition is reversed, oxygen is not effectively delivered throughout the patient’s body. There is, however, treatment available for the condition.
On February 8, 2006, the Veterans Health Administration (VA) announced the decision to stop the use of benzocaine sprays for these purposes. The FDA is currently reviewing all available safety data, but does not plan to remove the drugs from the market at this time.
Up until now, the FDA has concluded that the number of reported health problems associated with these sprays has been low and, when properly used, these products can help ameliorate discomfort for patients during these important procedures.
The VA health system is removing benzocaine sprays from their practice because they believe other topical anesthetics are less likely to cause methemoglobinemia and because the procedures themselves might cause similar signs, suggesting that methemoglobinemia may occur but go unrecognized in some cases.
This advisory applies only to benzocaine sprays used in the mouth and throat. It does not apply to other benzocaine products or to benzocaine sprays applied to exterior skin.
The FDA will make further announcements or take action as more information becomes available after the ongoing review.
In the meantime, the FDA offers the following suggestions about the use of benzocaine sprays in procedures requiring that a tube be inserted down the throat, windpipe, or gullet, or in minor surgical procedures performed in these areas.
• Benzocaine sprays used in the mouth and throat can result in potentially dangerous levels of methemoglobinemia.
• 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 and may be candidates for other forms of therapy.
• Patients who may have greater tendency for elevated levels of methemoglobinemia, such as all children less than 4 months of age and older patients with certain in-born defects (such as glucose-6-phosphodiesterase (G-6-PD) deficiency, hemoglobin-M disease, NADH-methemoglobin reductase (diaphorase 1) deficiency, and pyruvate-kinase deficiency) may benefit from products with different active ingredients such as lidocaine.
• Patients who receive benzocaine sprays should be given the minimum amount needed, to reduce the risks associated with methemoglobinemia.
• Patients who receive benzocaine sprays should be carefully observed for signs of methemoglobinemia including pale, gray, or blue colored skin, headache, lightheadedness, shortness of breath, anxiety, fatigue, and tachycardia (rapid heart rate).
• Methemoglobinemia makes a standard device used to assess the amount of oxygen bound to hemoglobin (2-wavelength pulse oximetry) unreliable. If blood is drawn to check for the condition, a co-oximeter is needed to reliably detect methemoglobinemia.
• A characteristic color of the blood (chocolate-brown rather than blood-red) can be a danger sign, but these changes are a late sign of the condition.
• Patients suspected of having high levels of methemoglobinemia should be promptly treated.
Effects of methemoglobinemia range from headache to cyanosis, which in the most severe cases can be life-threatening. Smokers, patients with chronic breathing problems, such as asthma or emphysema, and patients with heart disease, may be more susceptible to the problems from methemoglobinemia and may be more vulnerable to bad effects from this condition at lower levels of methemoglobin than healthy individuals.
Patients who lack or have reduced level of enzymes that help reverse the methemoglobinemia are also more susceptible to risks associated with benzocaine sprays.
The FDA has received reports of adverse health effects linked to benzocaine sprays together with symptoms that probably indicated methemoglobinemia in the patients. These cases, though, were received over a period of many years and this is an uncommon adverse event. The FDA is reviewing all available safety information for these affected Benzocaine sprays are marketed under different names, including Hurricaine, Topex, and Cetacaine products. In addition to benzocaine, Cetacaine® also contains butyl aminobenzoate and tetracaine as active ingredients.