Use of topical lidocaine for cosmetic dermatologic procedures

Journal of Drugs in Dermatology, Nov, 2007 by Divya Railan, Tina S. Alster

Abstract

Topical anesthetic agents are frequently used by dermatologists to decrease the pain associated with a variety of cutaneous procedures, including laser surgery, soft tissue augmentation, and other cosmetic surgical treatments. These lidocaine-containing creams play an integral role in the cosmetic dermatology office by providing patient comfort with minimal side effects. This review of topical lidocaine preparations should aid practitioners in the selection of an appropriate topical anesthetic, taking into consideration its onset and duration of action and potential side effects.

Introduction

As societal acceptance of rejuvenating techniques increases and the baby boomer population continues to age, dermatologists will experience growth in the demand for cosmetic procedures. The most rapidly growing segment is in the arena of nonsurgical cosmetic procedures, which includes injectable fillers and Botox[R], laser skin rejuvenation, and hair removal. These procedures provide patients with rapid aesthetic improvement and require minimal post-treatment recovery time. There are a variety of topical lidocaine-containing anesthetic preparations available for use prior to these cosmetic dermatologic procedures that reduce patient discomfort, thus helping to provide a more comfortable treatment experience. (1,2)

Classification of Anesthetics

Local anesthetics structurally consist of 3 parts: 1) an aromatic ring, 2) an intermediate chain, and 3) an amine group. The intermediate chain, which connects the aromatic and amine portions, is composed of either an ester or an amide linkage and is used in classifying local anesthetics into the amide and ester classes. The aromatic ring is lipophilic and is fundamentally important in enabling the anesthetic's diffusion through the highly lipophilic nerve membrane where depolarization is prevented by the blockage of sodium ion influx. Topical anesthetics traverse the superficial layers of the skin and affect the nerve endings within the dermis.

Topical Lidocaine

Lidocaine is the most commonly used topical anesthetic. It belongs to the amide class of anesthetics (including prilocaine and bupivacaine), which is used more often than the ester class of anesthetics (including procaine and tetracaine) due to the decreased incidence of allergic reactions associated with the amide class.

Although a multitude of lidocaine-containing topical anesthetic preparations exists, each differs in cost, formulation, and efficacy. Topical anesthetics may also vary with respect to recommended application time, necessity for occlusion, vehicle utilized, maximum safe dose, and duration of anesthetic effect. When selecting a topical anesthetic, it should be noted that combinations of various topical anesthetics can have additive toxicity potential. The risk of toxicity can also be amplified by application of lidocaine to a large surface area or application under occlusion.

The options available to anesthetize the skin continue to grow, particularly in the arena of compounded mixtures of lidocaine, which has no regulatory guidelines. Compounded topical anesthetic preparations (eg, benzocaine, lidocaine, tetracaine, or BLT) were recently implicated in 4 deaths after being applied to large surface areas prior to minor outpatient procedures. (3) Such unfortunate outcomes accentuate the need for patient education on the proper usage and potential dangers of the medication being used. Specifically, the patient should be counseled on the appropriate use of the medication and its increased risk of side effects when applied: 1) under occlusion, 2) to a large surface area, or 3) for periods longer than the manufacturer-recommended application time.

Although the incidence of systemic adverse reactions is low, clinicians should be aware of the signs of toxicity which initially include drowsiness and tingling of the lips and later tinnitus, dizziness, muscle twitches, seizures, and eventually respiratory distress and coma (Table 1). Because significant differences exist in the topical anesthetic products available, the manufacturer instructions for use should be closely followed in order to minimize the likelihood of side effects.

Two of the more popular lidocaine-containing topical anesthetic formulations are EMLA[R] cream (Astra Pharmaceuticals, Westborough, MA) and LMX[R] cream (Ferndale Laboratories, Ferndale, MI). (2,3) EMLA cream contains a eutectic mixture of 2.5% lidocaine and 2.5% prilocaine. The depth of anesthesia following EMLA application under occlusion was demonstrated in a study by Wahlgren and Quiding in which EMLA was applied under occlusion to the legs and achieved anesthesia to an average depth of 2.9 mm. (4)

LMX contains lidocaine in a liposomal delivery system with several lipid bilayers to facilitate the penetration of anesthetic into the skin while also protecting the drug from being rapidly metabolized, thereby allowing a prolonged duration of action. (5) LMX has been shown to produce effective anesthesia to laser-induced pain stimuli after a 60-minute application period under an occlusive dressing. (6) This study indicated that liposomal encapsulation provided increased efficacy in the delivery of anesthetic into the dermis. Compared to other topical anesthetics, LMX was significantly better than betacaine-LA or tetracaine after the 60-minute application time as well as 30 minutes later. (6) Although the data favored LMX over EMLA, the difference was not statistically significant. Increased anesthetic benefit was obtained 30 minutes after removal, which suggests that a reservoir of anesthetic is located and stored in the upper skin layers during application, providing additional anesthetic benefit after removal. (5,6)