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Adverse Reactions Hematologic: Methemoglobinemia Local: Burning, contact dermatitis, edema, erythema, pruritus, rash, stinging, tenderness, urticaria Miscellaneous: Hypersensitivity Contraindications Hypersensitivity to benzocaine, other ester-type local anesthetics, or any component; secondary bacterial infection of area; perforated tympanic membrane (otic formulations only) Warnings Benzocaine gels, liquids, and sprays used in the mouth, throat, and other mucous membranes have been associated with an increased risk for developing methemoglobinemia; methemoglobinemia is a serious and potentially fatal condition in which the amount of oxygen carried through the blood stream is greatly reduced; signs and symptoms may include pale-, gray-, or blue-colored skin, lips, and nail beds; headache; lightheadedness; shortness of breath; fatigue; and rapid heart rate and have been reported to appear within minutes to hours of applying benzocaine and may occur with the first application or prolonged use. The majority of cases associated with benzocaine use have been in infants and children <2 years of age for treatment of teething pain; also at greater risk for development are patients with asthma, bronchitis, emphysema, mucosal damage, or inflammation at the application site, heart disease, and malnutrition. The classical clinical finding of methemoglobinemia is chocolate brown-colored arterial blood; however, suspected cases should be confirmed by co-oximetry, which yields a direct and accurate measure of methemoglobin levels (standard pulse oximetry readings or arterial blood gas values are not reliable). The FDA recommends avoidance of self-treatment of OTC products for teething pain in infants and children <2 years of age; use cautiously in other patients or select another product. Clinically significant methemoglobinemia requires immediate treatment. Patients with a greater tendency for elevated levels of methemoglobin, eg, G-6-PD deficiency, hemoglobin-M disease, NADH-methemoglobin reductase deficiency, and pyruvate-kinase deficiency may benefit from products with an alternative anesthetic (eg, lidocaine).

Warnings Benzocaine gels, liquids, and sprays used in the mouth, throat, and other mucous membranes have been associated with an increased risk for developing methemoglobinemia; methemoglobinemia is a serious and potentially fatal condition in which the amount of oxygen carried through the blood stream is greatly reduced; signs and symptoms may include pale-, gray-, or blue-colored skin, lips, and nail beds; headache; lightheadedness; shortness of breath; fatigue; and rapid heart rate and have been reported to appear within minutes to hours of applying benzocaine and may occur with the first application or prolonged use. The majority of cases associated with benzocaine use have been in infants and children <2 years of age for treatment of teething pain; also at greater risk for development are patients with asthma, bronchitis, emphysema, mucosal damage, or inflammation at the application site, heart disease, and malnutrition. The classical clinical finding of methemoglobinemia is chocolate brown-colored arterial blood; however, suspected cases should be confirmed by co-oximetry, which yields a direct and accurate measure of methemoglobin levels (standard pulse oximetry readings or arterial blood gas values are not reliable). The FDA recommends avoidance of self-treatment of OTC products for teething pain in infants and children <2 years of age; use cautiously in other patients or select another product. Clinically significant methemoglobinemia requires immediate treatment. Patients with a greater tendency for elevated levels of methemoglobin, eg, G-6-PD deficiency, hemoglobin-M disease, NADH-methemoglobin reductase deficiency, and pyruvate-kinase deficiency may benefit from products with an alternative anesthetic (eg, lidocaine). Topical use prior to cosmetic procedures can result in high systemic levels and lead to toxic effects (eg arrhythmias, seizures, coma, respiratory depression, and death), particularly when applied in large amounts to cover large areas and/or left on for long periods of time or used with materials, wraps, or dressings to cover the skin after anesthetic application. These practices may increase the degree of systemic absorption and should be avoided. The FDA is recommending consumers consult their healthcare provider for instructions on safe use prior to applying topical anesthetics for medical or cosmetic purposes. Use of products with the lowest amount of anesthetic with the least amount of application possible to relieve pain is also recommended.

Topical use prior to cosmetic procedures can result in high systemic levels and lead to toxic effects (eg arrhythmias, seizures, coma, respiratory depression, and death), particularly when applied in large amounts to cover large areas and/or left on for long periods of time or used with materials, wraps, or dressings to cover the skin after anesthetic application. These practices may increase the degree of systemic absorption and should be avoided. The FDA is recommending consumers consult their healthcare provider for instructions on safe use prior to applying topical anesthetics for medical or cosmetic purposes. Use of products with the lowest amount of anesthetic with the least amount of application possible to relieve pain is also recommended. Some products contain tartrazine and benzyl alcohol which may cause allergic reactions in susceptible individuals; large amounts of benzyl alcohol (≥99 mg/kg/day) have been associated with a potentially fatal toxicity (“gasping syndrome”) in neonates; the “gasping syndrome” consists of metabolic acidosis, respiratory distress, gasping respirations, CNS dysfunction (including convulsions, intracranial hemorrhage), hypotension and cardiovascular collapse; avoid use of injection in neonates. In vitro and animal studies have shown that benzoate, a metabolite of benzyl alcohol, displaces bilirubin from protein-binding sites. Metabolism/Transport Effects None known. Drug Interactions (For additional information: Launch Lexi-Interact™ Drug Interactions Program ) Prilocaine: Methemoglobinemia Associated Agents may enhance the adverse/toxic effect of Prilocaine. Combinations of these agents may increase the likelihood of significant methemoglobinemia. Management: Monitor patients for signs of methemoglobinemia (e.g., hypoxia, cyanosis) when prilocaine is used in combination with other agents associated with development of methemoglobinemia. Avoid lidocaine/prilocaine in infants receiving such agents. Risk C: Monitor therapy Pregnancy Risk Factor C ( show table ) Pregnancy Implications Reproduction studies have not been conducted. Monitoring Parameters Monitor patients for signs and symptoms of methemoglobinemia such as pallor, cyanosis, nausea, muscle weakness, dizziness, confusion, agitation, dyspnea, and tachycardia; co-oximetry

Prilocaine: Methemoglobinemia Associated Agents may enhance the adverse/toxic effect of Prilocaine. Combinations of these agents may increase the likelihood of significant methemoglobinemia. Management: Monitor patients for signs of methemoglobinemia (e.g., hypoxia, cyanosis) when prilocaine is used in combination with other agents associated with development of methemoglobinemia. Avoid lidocaine/prilocaine in infants receiving such agents. Risk C: Monitor therapy Pregnancy Risk Factor C ( show table ) Pregnancy Implications Reproduction studies have not been conducted. Monitoring Parameters Monitor patients for signs and symptoms of methemoglobinemia such as pallor, cyanosis, nausea, muscle weakness, dizziness, confusion, agitation, dyspnea, and tachycardia; co-oximetry Mechanism of Action Blocks both the initiation and conduction of nerve impulses from sensory nerves by decreasing the neuronal membrane's permeability to sodium ions, which results in inhibition of depolarization with resultant blockade of conduction Pharmacokinetics (Adult data unless noted) Absorption: Poor after topical administration to intact skin, but well absorbed from mucous membranes and traumatized skin Metabolism: Hydrolyzed in plasma and to a lesser extent in the liver by cholinesterase Elimination: Excretion of the metabolites in urine Patient Information (For additional information see "Benzocaine: Patient drug information" ) Consult healthcare provider for safe application practice prior to application; do not eat for 1 hour after application to oral mucosa; do not chew gum while mouth or throat is anesthetized due to potential biting trauma; do not overuse; do not apply to infected areas or to large areas of broken skin Use of UpToDate is subject to the Subscription and License Agreement . Topic 13008 Version 34.0 © 2013 UpToDate, Inc. All rights reserved. | Subscription and License Agreement | Release: 21.3 - C21.34 Licensed to: Morehouse School of Medicine | Support Tag: [0503-189.41.181.191-2D925142A9-S473950.14]