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EMLA
EMLA
EMLA is a 2.5% eutectic mixture of lidocaine and prilocaine that is packaged commercially as a cream or patch.5 It is one of the most common topical agents used in
dermatology and available via prescription. The definition of a eutectic mixture is one in which the ingredients are formulated to melt to liquid phase at room temperature.41,52 In addition to the two active anesthetic agents, EMLA contains emulsifiers (polyoxyethylene), thickening agents (carboxypolymethylene), and distilled water.5 It has been effectively used prior to laser surgery, chemical peels, graft procedures, skin biopsies, and electrosurgery procedures.41,43
To work effectively, EMLA is usually applied under occlusion with either a plastic wrap or dressing.6 Numbing effectiveness depends, in part, on the anatomic area being treated and the duration of the occlusion. For example, on the face, anesthesia can occur in 30 minutes or less, whereas on mucous membranes it only takes 5 to 15 minutes.6 Most dermatologists leave EMLA on the skin for at least 1 hour and, for more painful procedures, 2 to 3 hours with occlusion.5,41 The maximum effect of anesthesia is reached within 2 to 3 hours after application. EMLA penetrates 3 mm into the skin after 1 hour of application and 5 mm after 2 hours.41
Like other amide anesthetics, EMLA should use cautiously in conditions where the skin integrity is breached, such as psoriasis and eczema.53 It is contraindicated in those with liver disease and amide hypersensitivity.53 Care also must be taken when using EMLA around the eyes.54
Pharmacy-compounded topical anesthetics Topical anesthetics are in some instances compounded by pharmacies for use in dermatology. Standardization of compounded products proves difficult because individual pharmacies use different protocols to mix various ingredients in their topical anesthetics.55,56 Formula standardization should be considered for compounded anesthetics, since the formulations are not regulated by the FDA and may be inconsistent.57 As compounded anesthetics do not require clinical trials, there is a great variability in use.56 Mixtures are usually made using various concentrations of lidocaine, Betacaine, and tetracaine.6,56 Care must be taken when using compounded topical anesthetics and choosing the right company to manufacture them. Particulate matter has been shown in one case to cause corneal abrasions due to issues with a particular benzocaine 20%, lidocaine 6%, and tetracaine 4% (BLT) preparation.57 It is essential that the dermatologist develops a working relationship with a reputable compounding pharmacy and not exceeds the dosages established for traditional topical and/or injectable anesthetic agents. The use of pharmacy- compounded topical anesthetics should only be performed under the direct supervision of a physician and conservatively applied to limited body areas.