Eutectic Mixture of Local Anesthetics
EMLA contains lidocaine 2.5% and prilocaine 2.5% as an oil-in-water emulsion. By definition, a eutectic mixture has a melting point that is lower than either constituent alone; therefore, this mixture of lidocaine and prilocaine in a 1:1 ratio is present in liquid phase. EMLA is available commercially as cream, gel, and anesthetic disc. The cream and the disc are approved for topical use in children undergoing minor (e.g., venipuncture) and major (e.g., skin-graft harvesting) dermal procedures. The cream can be used in either setting, whereas the disc should be used only during minor procedures because of its inability to cover more than a limited surface area (up to 40 cm2).
A concern with EMLA is the risk of systemic absorption; however, absorption is minimal and should not produce toxic plasma levels with routine dosing, even when applied to open wounds. When applied to the skin, an anesthetic response occurs within 45 to 60 minutes and lasts for one to two hours after removal. Additionally, the site of application can affect the duration of analgesia; areas with increased vasculature can increase drug clearance. Dosing for EMLA is age- and weight-based, and the manufacturer recommends the following: age 0-3 months or < 5 kg should receive 1 g over 10 cm2 skin for up to 1 hour; age 3-12 months and > 5 kg should receive 2 g over 20 cm2 skin for up to 4 hours; age 1-6 years and > 10 kg should receive 10 g over 100 cm2 skin for up to 4 hours; and age 7-12 years and > 20 kg should receive 20 g over 200 cm2 skin for up 4 hours. For maximum skin absorption, EMLA should be applied beneath occlusive dressings such as Tegaderm. Because of the risk of methemoglobinemia, EMLA use should be avoided in neonates with a gestational age of less than 37 weeks and in infants under the age of 1 year who are receiving concomitant therapy with agents such as phenytoin or acetaminophen.
EMLA has demonstrated efficacy in reducing pain in infants and children who have undergone procedures such as venipuncture. In a trial of chronically ill infants and toddlers, mean visual analog pain scale scores were significantly lower with the use of EMLA cream versus placebo (P =.01). When serum methemoglobin was monitored, levels were similar in both groups and did not increase beyond normal range. Another trial evaluating pain response and ease of venipuncture found that the 20 children who received EMLA had lower pain scores (P ≤ .01) and significant improvements in ease of venipuncture (P ≤ .05).
US Pharmacist. 2009;34(3):HS-4- HS-7. © 2009 Jobson Publishing
Cite this: Topical Anesthesia Use in Children - Medscape - Mar 01, 2009.