From the Guidelines
Benzocaine is a topical anesthetic medication that can be used to temporarily relieve pain and discomfort on the skin and mucous membranes, but it carries a risk of methemoglobinemia, particularly with prolonged use or in large surface areas. According to the guidelines for the use of local anesthesia in office-based dermatologic surgery 1, benzocaine has an onset of action of 5 minutes and a duration of action of 15-45 minutes. Some key points to consider when using benzocaine include:
- It is available in various concentrations, typically ranging from 5% to 20%
- It should be applied only to the affected area as directed on the product label, usually no more than 3-4 times daily
- The minimum effective amount should be used, and prolonged use without medical supervision should be avoided
- There is a risk of methemoglobinemia, especially in children under two years old, which can reduce the blood's ability to carry oxygen
- Symptoms of methemoglobinemia include pale, gray, or blue-colored skin, lips, or nail beds, shortness of breath, fatigue, confusion, or rapid heart rate, and require immediate medical attention if they occur. It's also worth noting that benzocaine is just one of several topical anesthetics available, and other options like lidocaine and tetracaine may be equally effective in certain situations, as shown in a systematic review of 22 trials encompassing 3000 patients 1.
From the FDA Drug Label
Active ingredient Benzocaine 20.0% (w/w) Benzocaine is an active ingredient with a concentration of 20.0% (w/w), as per the drug label 2.
- It is the primary component of the medication.
- The exact nature or classification of benzocaine (e.g., anesthetic, etc.) is not explicitly stated in the provided drug labels.
From the Research
Definition and Uses of Benzocaine
- Benzocaine is a local anesthetic commonly used for topical application to relieve pain or discomfort [(3,4,5,6)].
- It is often used in medical procedures, such as endoscopy, to numb the area and reduce pain [(4,6)].
- Benzocaine can be found in various forms, including sprays, ointments, and gels [(3,5)].
Association with Methemoglobinemia
- Benzocaine has been linked to methemoglobinemia, a rare but potentially life-threatening condition [(3,4,5,6)].
- Methemoglobinemia occurs when the iron in hemoglobin is stabilized in the ferric form, making it unable to bind oxygen and leading to tissue hypoxia 7.
- Symptoms of methemoglobinemia include cyanosis, respiratory distress, headache, lightheadedness, and dark, chocolate-colored blood [(3,4,5,6)].
Importance of Recognition and Treatment
- Prompt recognition of methemoglobinemia is crucial, as it can be fatal if left untreated [(4,6)].
- Treatment with methylene blue is generally effective in reducing methemoglobin levels and alleviating symptoms [(3,4,5,6)].
- Healthcare professionals should be aware of the risks associated with benzocaine and monitor patients closely for signs of methemoglobinemia [(7,6)].