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The Effects of Benzocaine

written by: Robyn Broyles•edited by: Leigh A. Zaykoski•updated: 8/5/2009

Is benzocaine dangerous? Or is it a useful medicine for numbing pain? What you need to know about the side effects of benzocaine.

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    Benzocaine Facts

    Benzocaine is a local anesthetic used for numbing skin and surfaces in the oral cavity (mouth). Related to novocain (widely used in dentistry) and lidocaine, benzocaine blocks the ability of sensory nerves to send information to the brain. When treated with benzocaine, the skin and oral membranes temporarily lose the ability to feel pain and other sensations. The numbing effects of benzocaine can give relief to people suffering from localized pain.

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    Uses

    Benzocaine is the active ingredient in Anbesol, Orajel Medicine Gel, and similar products for soothing mouth pain. These products may be used for treating mouth ulcers (canker sores), toothaches, and teething pain in babies. The ingredient is also available in spray and lozenge form for treating sore throats.

    Benzocaine preparations for use in the ear are available. Brands include Americaine and Otocain. These products are used to relieve ear pain associated with ear infections (otitis) or surgery. It does not treat the underlying cause of the ear pain, unlike antibiotic ear drops.

    When selecting an over-the-counter benzocaine product, read the labels of each product carefully. Some products with the same brand name have very different active ingredients. For example, Orajel Baby is a benzocaine preparation for teething pain, but Orajel Toddler is a toothpaste and contains no benzocaine.

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    Side Effects and Warnings

    Benzocaine can cause allergic reactions, including anaphylaxis. People with allergies to benzocaine or similar numbing agents, or to PABA (the base molecule of benzocaine), should avoid benzocaine-containing products.

    When benzocaine is used in the throat, the numbing action can suppress the gag reflex. Sleeping or unconscious people are put at an increased risk of aspirating vomit or saliva, which can cause airway obstruction (choking) or pneumonia. These products should be used with caution before bedtime.

    One of the rare effects of benzocaine is serious medical condition called methemoglobinemia. This condition occurs when the hemoglobin in the blood is converted to a form that cannot carry oxygen to cells. Methemoglobinemia can be triggered by benzocaine when the amount used exceeds the recommended dosage, and is more likely in people with impaired respiration (i.e. smokers or people with asthma, emphysema, or heart disease). Symptoms include shortness of breath, dizziness, and blue or gray color to the extremities (cyanosis). Pulse oximetry, the most common way to monitor blood oxygen in health care settings, is not able to detect methemoglobinemia, which requires specialized tests to confirm.

    The Veterans Administration (VA) recently stopped the use of benzocaine sprays in its hospitals because of the risk of methemoglobinemia. Benzocaine sprays are commonly used to numb the throat before insertion of breathing tubes or other procedures. The Food and Drug Administration (FDA) responded with an opinion that the benefits of benzocaine sprays generally outweigh the risks, but care must be taken to use these products correctly.

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    References