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Concerns related to adverse effects: • Methemoglobinemia: Has been reported following topical benzocaine use (rare), particularly with higher concentration (14% to 20%) spray formulations applied to the mouth or mucous membranes. 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. Clinically-significant methemoglobinemia requires immediate treatment. Use caution with breathing problems (asthma, bronchitis, emphysema, in smokers), inflamed/damaged mucosa, heart disease, children <6 months of age, and hemoglobin or enzyme abnormalities (glucose-6-phosphate dehydrogenase deficiency, hemoglobin-M disease, NADH-methemoglobin reductase deficiency, pyruvate-kinase deficiency). Alternatives to benzocaine sprays, such as topical lidocaine preparations, should be considered for patients at higher risk of this reaction.

Special populations: • Acutely ill patients: Use with caution in acutely ill patients; dose adjustment is suggested. • Debilitated patients: Use with caution in debilitated patients; dose adjustment is suggested. • Elderly: Use with caution in the elderly; dose adjustment is suggested. • Pediatrics: Use with caution in very young patients; dose adjustment is suggested.

Other warnings/precautions: • Administration: For topical use only. Do not use under dentures or cotton rolls; retention of active ingredients may cause escharotic effect. • Topical application: When topical anesthetics are used prior to cosmetic or medical procedures, the lowest amount of anesthetic necessary for pain relief should be applied. High systemic levels and toxic effects (eg, methhemoglobinemia, irregular heart beats, respiratory depression, seizures, death) have been reported in patients who (without supervision of a trained professional) have applied topical anesthetics in large amounts (or to large areas of the skin), left these products on for prolonged periods of time, or have used wraps/dressings to cover the skin following application. Metabolism/Transport Effects None known. Drug Interactions (For additional information: Launch Lexi-Interact™ Drug Interactions Program ) There are no known significant interactions. Pregnancy Implications Safety has not been established; use is not recommended during early pregnancy unless the potential benefits outweigh the risks. Monitoring Parameters Monitor patients for signs and symptoms of methemoglobinemia such as pallor, cyanosis, nausea, muscle weakness, dizziness, confusion, agitation, dyspnea and tachycardia. 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. Clinically significant methemoglobinemia requires immediate treatment. Mechanism of Action Reversible blockage of initiation and conduction of nerve impulses by decreasing the neuronal membrane’s permeability to sodium ions Pharmacodynamics/Kinetics Also see individual monographs for Benzocaine and Tetracaine. Onset of action: ~30 seconds Duration: 30-60 minutes Metabolism: Plasma via hydrolysis by cholinesterase to inactive metabolites Excretion: Urine (as inactive metabolites) Use of UpToDate is subject to the Subscription and License Agreement . Topic 8818 Version 28.0 © 2013 UpToDate, Inc. All rights reserved. | Subscription and License Agreement | Release: 21.4 - C21.36 Licensed to: Southeast Alabama Med Ctr | Support Tag: [0503-61.234.146.186-2332FC6495-S244013.14]