Part II. Topical Anesthesia

OFFICE PROCEDURES

Principles of Office Anesthesia: Part II. Topical Anesthesia SURITI KUNDU, M.D., Scripps Clinic, San Diego, California SURAJ ACHAR, M.D., University of California, San Diego, School of Medicine, La Jolla, California

The development of topical anesthetics has provided the family physician with multi- ple options in anesthetizing open and intact skin. The combination of tetracaine, adrenaline (epinephrine), and cocaine, better known as TAC, was the first topical agent available for analgesia of lacerations to the face and scalp. Cocaine has been replaced with lidocaine in a newer formulation called LET (lidocaine, epinephrine, and tetracaine). For analgesia to nonintact skin, LET gel is generally preferred over TAC because of its superior safety record and cost-effectiveness. EMLA (eutectic mixture of local anesthetics) is perhaps the most well-known topical anesthetic for use on intact skin. EMLA can be used to anesthetize the skin before intramuscular injections, venipunc- ture, and simple skin procedures such as curettage or biopsy. To be fully effective, EMLA should be applied at least 90 minutes before the procedure. ELA-Max is a new, rapidly acting topical agent for intact skin that works by way of a liposomal delivery system and is available over the counter. Other delivery vehicles for topical anesthesia currently in development, including iontophoresis and anesthetic patches, may one day give patients and physicians even more flexibility. (Am Fam Physician 2002;66:99- 102. Copyright© 2002 American Academy of Family Physicians.)

This article is one in a opical anesthetics were devel- 2 to 5 mL of solution is applied directly to the series of “Office Proce- oped in the latter half of the 19th wound using a cotton-tipped applicator with dures” articles coordi- century, starting with a descrip- firm pressure that is maintained for 20 to nated by Suraj Achar, 2,3 M.D., Director of Fam- tion of the topical uses for 40 minutes. However, the use of TAC is no ily Medicine Selective, cocaine.1 However, it has taken longer supported by the literature because of University of California, nearlyT a whole century for effective and safe general concern about toxicity and expense, San Diego, School of topical anesthetics to become readily available. and federal regulatory issues involving med- Medicine, La Jolla. Today, pain can be effectively alleviated for ications containing cocaine. such procedures as cryotherapy, shave biopsy, and curettage of molluscum contagiosa. Pro- Lidocaine, Epinephrine, and Tetracaine cedures such as laceration repair, which at one To create a safer and more cost-effective time required the use of painful infiltrative alternative to TAC, 4 percent lidocaine (Xylo- anesthetics, can now be accomplished safely caine) was substituted for cocaine and com- and comfortably with the use of topical anes- bined with 0.1 percent epinephrine and thetics. An additional advantage of topical 0.5 percent tetracaine to create a newer topical anesthetics in laceration repair is that wound anesthetic (lidocaine, epinephrine, and tetra- margins are not distorted. A summary of var- caine [LET]). It is not available commercially ious topical anesthetics is provided in Table 1. and must be compounded as a liquid or gel formulation. LET is used on nonmucosal skin Tetracaine, Adrenaline (Epinephrine), lacerations by placing a few drops directly into and Cocaine the wound. A cotton-tipped applicator with Tetracaine, adrenaline, and cocaine (TAC), a 1 to 3 mL of the gel or solution is then applied This is part II of a two- compound of 0.5 percent tetracaine (Ponto- directly to the wound with firm pressure for part article on office caine), 0.05 percent epinephrine, and 11.8 per- 15 to 30 minutes.4,5 Both the solution and the anesthesia. Part I, “Infiltrative Anesthe- cent cocaine, was the first topical anesthetic gel have been safely used in children older sia,” appears on page mixture found to be effective for nonmucosal than two years of age, and both forms are 91 of this issue. skin lacerations to the face and scalp.2 From equally effective.6 Anesthetic failure rates for

JULY 1, 2002 / VOLUME 66, NUMBER 1 www.aafp.org/afp AMERICAN FAMILY PHYSICIAN 99 as the digits, should be avoided. Caution must A liposomal delivery system consisting of 4 percent lidocaine also be exercised when contemplating the use cream is now available as an over-the-counter product and of LET in contaminated wounds, complex wounds, or wounds larger than 6 cm. LET and has been approved for temporary pain relief of minor cuts TAC do not work on intact skin. and abrasions. Eutectic Mixture of Local Anesthetics Most pure anesthetic agents exist as solids. repair of lacerations on the face and scalp with Eutectic mixtures are liquids and melt at lower LET gel were only about 5 percent in one temperatures than any of their components, study.7 LET is slightly less effective on extrem- permitting higher concentrations of anesthet- ity lacerations.7 If adequate anesthesia is not ics. Eutectic mixture of local anesthetics achieved topically, an infiltrative anesthetic (EMLA) represents the first major break- may be injected locally, provided the maximal through for dermal anesthesia on intact skin. lidocaine dosage of 3 to 5 mg per kg of lido- It consists of 25 mg per mL of lidocaine, caine is not exceeded. 25 mg per mL of prilocaine, a thickener, an There have been no reports of toxicity with emulsifier, and distilled water adjusted to a pH LET, but avoiding mucous membranes is rec- level of 9.4.3 ommended. When working near mucous EMLA is applied in a thick layer (1 to 2 g per membranes, LET gel is better than the solu- 10 cm2, up to a maximal dose of 10 g) to intact tion because it stays within the wound. skin.8 After application, the area is covered with Because LET contains epinephrine, applica- a patch of Tegaderm or clear plastic wrap to tion to end-arteriolar parts of the body, such facilitate penetration through the stratum

TABLE 1 Topical Anesthesia

Anesthetic product Methods Onset/duration Effectiveness Complications

TAC (0.5% tetracaine, 2 to 5 mL (1 mL per cm Onset: effective May be as effective as Rare severe toxicity, 1:2,000 epinephrine, of laceration) applied 10 to 30 minutes lidocaine for lacerations including seizures and and 11.8% cocaine) to wound with cotton after application on face and scalp sudden cardiac death or gauze for 10 to Duration: not 30 minutes established LET (4% lidocaine, 1 to 3 mL directly Onset: 20 to Similar to TAC for face No severe adverse 1:2,000 epinephrine, applied to wound for 30 minutes and scalp lacerations; less effects reported and 0.5% tetracaine) 15 to 30 minutes Duration: not effective on extremities established EMLA (2.5% lidocaine Thick layer (1 to 2 g per Onset: must be left Variable, depending on Contact dermatitis, and 2.5% prilocaine) 10 cm2) applied to intact on for 1 to 2 hours duration of application methemoglobinemia skin with covering Duration: 0.5 to (very rare) patch of Tegaderm 2 hours Iontophoresis Small current applied Onset: 10 minutes Good for small procedures, Stinging sensation; to lidocaine-soaked Duration: 10 to depth of anesthesia may burn skin if high sponges on intact skin 20 minutes greater than EMLA current

TAC = tetracaine, adrenaline, and cocaine; LET = lidocaine, epinephrine, and tetracaine; EMLA = eutectic mixture of local anesthetics.

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Iontophoresis is a method of delivering a topical anesthetic to intact skin.

months of age who were exposed to high doses of EMLA for prolonged periods.8 Since then, other studies have demonstrated that 1 g of EMLA applied to the penis for one hour is safe to use in healthy, full-term neonates FIGURE 1. Thick layer of EMLA (eutectic mix- 13,14 ture of local anesthetics) applied to intact before circumcision. Although using skin, with a covering layer of Tegaderm. EMLA is better than using no anesthesia at all, the dorsal penile nerve block still offers superior analgesia before circumcision, and the corneum (Figure 1). Depth of anesthesia methods may be combined.13 depends on contact time with EMLA. Anes- thetic effect has been shown to reach a maximal Liposomes depth of 3 mm after a 60-minute application, Liposomes are comprised of lipid layers and 5 mm after a 120-minute application.9 It surrounded by aqueous layers. They are able was also found that dermal analgesia continues to penetrate the stratum corneum because and may even increase for 30 to 60 minutes they resemble the lipid bilayers of the cell after the cream is removed.9 EMLA should not membrane. A liposomal delivery system be applied to the palms and soles because of recently became available as an over-the- variable penetration. counter product called ELA-Max. It contains EMLA has been approved by the U.S. Food 4 percent lidocaine cream in a liposomal and Drug Administration (FDA) only for use matrix and is FDA-approved for the tempo- on intact, nonmucosal skin. Recent studies rary relief of pain resulting from minor cuts have shown that EMLA can also be effectively and abrasions. ELA-Max is applied to intact used on extremity lacerations. One study skin for 15 to 40 minutes without occlusion.15-17 showed that 85 percent of children whose lac- In limited studies, ELA-Max has also proved erations were treated with EMLA required no effective in providing dermal analgesia before further anesthesia before suturing.10 The chemical peeling.18 The safety of its applica- drawback is the 90-minute wait required tion to mucous membranes has not been eval- between the application of EMLA and onset uated.5 Despite a paucity of data and lack of of laceration repair. EMLA has been shown to an FDA indication, clinicians are beginning to work effectively on genital mucosa in a study use ELA-Max for topical anesthesia before of women undergoing laser treatment of other dermatologic procedures. condylomata acuminata.11 Current studies have not established safe and optimal dosages Anesthetic Patches for either of these off-label uses.10 Several anesthetic patch preparations using EMLA has been associated with occasional varying concentrations of lidocaine have adverse reactions, including blanching and shown promise for topical anesthesia. The lido- redness at the application site.8,12 Perhaps the caine gel patch known as Lidoderm was most serious complication is methemoglo- recently approved by the FDA for the treatment binemia. Cases of methemoglobinemia have of pain caused by postherpetic neuralgia, but it occurred in infants younger than three has not been studied for use in procedures.

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4. Keyes PD, Tallon JM, Rizos J. Topical anesthesia. Can Fam Physician 1998;44:2152-6. 5. Ernst AA, Marvez-Valls E, Nick TG, Mills T, Minvielle L, Houry D. Topical lidocaine adrenaline tetracaine (LAT gel) versus injectable buffered lidocaine for local anesthesia in laceration repair. West J Med 1997;167:79-81. 6. Resch K, Schilling C, Borchert BD, Klatzko M, Uden D. Topical anesthesia for pediatric lacerations: a randomized trial of lidocaine-epinephrine-tetracaine solution versus gel. Ann Emerg Med 1998; 32:693-7. 7. Ernst AA, Marvez E, Nick TG, Chin E, Wood E, Gonzaba WT. Lidocaine adrenaline tetracaine gel versus tetracaine adrenaline cocaine gel for topical FIGURE 2. Iontophoresis applied to the shoulder. anesthesia in linear scalp and facial lacerations in children aged 5 to 17 years. Pediatrics 1995; 95:255-8. 8. Eichenfield LF, Cunningham BB. Decreasing the Iontophoresis pain of dermatologic procedures in children. Clin Iontophoresis is a method of delivering a Prob Dermatol 1999;11:1-36. 9. Bjerring P, Arendt-Nielson L. Depth and duration of topical anesthetic with a mild electric current. skin analgesia to needle insertion after topical Lidocaine-soaked sponges are applied to application of EMLA cream. Br J Anaesth 1990; intact skin, and electrodes are placed on top of 64:173-7. 10. Zempsky WT, Karasic RB. EMLA versus TAC for top- the anesthetic. A DC current is then applied to ical anesthesia of extremity wounds in children. the skin (Figure 2). The anesthetic effect Ann Emerg Med 1997;30:163-6. occurs within 10 minutes and lasts approxi- 11. Rylander E, Sjoberg I, Lillieborg S, Stockman O. Local anesthesia of the genital mucosa with a lido- mately 15 minutes. The depth of anesthesia caine/prilocaine cream (EMLA) for laser treatment can reach up to 1 to 2 cm.12 of condylomata acuminata: a placebo-controlled Although the effectiveness of iontophoresis study. Obstet Gynecol 1990;75:302-6. 12. Lener EV, Bucalo BD, Kist DA, Moy RL. Topical anes- has been compared favorably to that of thetic agents in dermatologic surgery. A review. EMLA, it remains underused. Some patients Dermatol Surg 1997;23:673-83. find the mild electrical sensation uncomfort- 13. Howard CR, Howard FM, Fortune K, Generelli P, Zolnoun D, tenHoopen C, et al. A randomized, able. The apparatus is expensive and bulky, controlled trial of a eutectic mixture of local anes- and cannot be used over large surface areas of thetic cream (lidocaine and prilocaine) versus the body.8 Other applications using ion- penile nerve block for pain relief during circumcision. Am J Obstet Gynecol 1999;181:1506-11. tophoresis are still being developed. 14. Essink-Tjebbes CM, Hekster YA, Liem KD, van Don- gen RT. Topical use of local anesthetics in neonates. The authors thank Lawrence Eichenfield, M.D., for Pharm World Sci 1999;21:173-6. review of the manuscript and recommendations. 15. Foldvari M. In vitro cutaneous and percutaneous delivery and in vivo efficacy of tetracaine from liposomal and conventional vehicles. Pharm Res The authors indicate that they do not have any con- 1994;11:1593-8. flicts of interest. Sources of funding: none reported. 16. Friedman PM, Fogelman JP, Nouri K, Levine VJ, Ashinoff R. Comparative study of the efficacy of REFERENCES four topical anesthetics. Dermatol Surg 1999;25: 950-4. 1. Dripps RD, Eckenhoff JE, Vandam LD, Longnecker 17. Bucalo BD, Mirikitani EJ, Moy RL. Comparison of DE, Murphy FL. Dripps/Eckenhoff/Vandam intro- skin anesthetic effect of liposomal lidocaine, nonli- duction to anesthesia. 8th ed. Philadelphia: Saun- posomal lidocaine, and EMLA using 30-minute ders, 1992. application time. Dermatol Surg 1998;24:537-41. 2. Pryor GJ, Kilpatrick WR, Opp DR. Local anesthesia 18. Koppel RA, Coleman KM, Coleman WP. The effi- in minor lacerations: topical TAC vs lidocaine infil- cacy of EMLA versus ELA-Max for pain relief in tration. Ann Emerg Med 1980;9:568-71. medium-depth chemical peeling: a clinical and 3. Whealton EG. Advances in office anesthesia. J Am histopathologic evaluation. Dermatol Surg 2000; Board Fam Pract 1998;11:200-6. 26:61-4.

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