ROCKVILLE, Md., Feb. 13 - The Veterans Health Administration has halted the use of benzocaine sprays to numb mucous membranes in the mouth and throat, prompting the FDA to reissue warnings about the risk of methemoglobinemia.
The reiterated FDA warning, originally issued three years ago, took the form of a Public Health Advisory, notifying healthcare professionals and patients about adverse events, including methemoglobinemia, associated with the use of benzocaine sprays used in the mouth and throat for minor surgical procedures.
The VA announced last week it would no longer use the sprays for those purposes.
"The FDA is aware of the reported adverse events and is reviewing all available safety data, but at this time is not planning action to remove the drugs from the market," the agency said.
The sprays, which are marketed under a variety of names including Hurricaine, Topex, and Cetacaine, are often used to facilitate insertion of nasogastric tubes or for minor surgeries.
The FDA statement warned that some reported cases of methemoglobinemia have resulted from medication errors because of incorrect use of benzocaine sprays (e.g., longer duration or more frequent sprays than recommended).
Methemoglobinemia impairs the ability of red blood cells to transport oxygen. As a result, patients can suffer from signs of oxygen deprivation such as headaches. If the condition is undetected and untreated, life-threatening cyanosis can develop.
Patients with a history of breathing disorders including asthma and emphysema, smokers and patients with heart disease may be particularly at risk when treated with the benzocaine sprays.
The VA said it decided to use other topical anesthetics, which it said are less likely to cause methemoglobinemia.
The FDA alert said that it "is important to note also that these cases were received over a period of many years and this is an uncommon adverse event."
The agency is continuing to review safety information for benzocaine sprays. Meanwhile, it advised physicians to consider these points when using the sprays:
- 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 younger than four months 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.