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      Effectiveness of various formulations of local anesthetics and additives for topical anesthesia – a prospective, randomized, double-blind, placebo-controlled study

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          Topical anesthesia is used to control pain associated with many procedures in medicine. Today, the product most commonly applied for topical anesthesia in Germany is EMLA ® (lidocaine/prilocaine). However, since prilocaine is a methemoglobin-inducing agent, there are limitations to its use, especially in neonates and infants. The aim of this study was to evaluate the effect of prilocaine and lidocaine as well as propylene glycol, a penetration enhancer, and trometamol, a buffer substance, in anesthetic creams.

          Patients and methods

          Twenty-nine healthy adults participated in this study. Standardized creams with eight different compositions were applied and left for 20, 40 or 60 min. After exposure to standardized painful stimuli (blunt/sharp with pressures of 0.2, 0.4 or 0.8 N), subjects rated the experimental pain using a visual analog scale.


          Significant results were only found with an exposure time of 60 min and a stamp pressure of 0.8 N. At a concentration of 20%, lidocaine was more effective compared to placebo and equally effective compared to lidocaine/prilocaine in controlling pain. The analgesic effect of the cream containing lidocaine 10% and additional trometamol was significantly superior to that of placebo and non-inferior to that of lidocaine/prilocaine. In this study, the penetration enhancer propylene glycol did not accelerate the onset of the analgesic effect. In contrast, the addition of trometamol (Tris/THAM) accelerated the onset of the effect compared to the native formulation (at 0.4 and 0.8 N). In all of the adult subjects of this study, the minimum exposure time was 60 min for any of the tested topical anesthetic creams.


          The results of this study indicate that a cream containing 20% lidocaine, 38% trometamol and 10% propylene glycol may be used as an alternative to lidocaine/prilocaine with a comparable effect and without the need to extend exposure time.

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          Most cited references 13

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          Heated lidocaine/tetracaine patch (Synera, Rapydan) compared with lidocaine/prilocaine cream (EMLA) for topical anaesthesia before vascular access.

          We compared the lidocaine/tetracaine patch [Synera (USA), Rapydan (Europe)], a novel heat-aided patch using a eutectic mixture of lidocaine 70 mg and tetracaine 70 mg, with a eutectic mixture of lidocaine 25 mg ml(-1) and prilocaine 25 mg ml(-1) (EMLA Cream). The agents were administered at different time periods for local topical anaesthesia before a vascular access procedure. In this double-blind, paired study, 82 adult volunteers were randomized to receive the lidocaine/tetracaine patch on one anticubital surface and lidocaine/prilocaine cream on the other concurrently for 10, 20, 30, or 60 min before a vascular access procedure. Subjects rated pain intensity using a 100 mm visual analogue scale (VAS). Skin reactions and adverse events were also evaluated. Median VAS scores were significantly lower for the lidocaine/tetracaine patch than for lidocaine/prilocaine cream in the 10 min (P=0.010), 20 min (P=0.042), and 30 min (P=0.001) application groups. The lidocaine/tetracaine patch was associated with significantly more erythema than lidocaine/prilocaine cream at 20, 30, and 60 min, whereas lidocaine/prilocaine cream produced more blanching than the lidocaine/tetracaine patch at 30 and 60 min. Two subjects reported nausea and faintness associated with the vascular access procedure; one was withdrawn from the study. The lidocaine/tetracaine patch provided effective anaesthesia with an application time as short as 10 min and was better than lidocaine/prilocaine cream at all application times shorter than 60 min, demonstrating a substantial improvement in time to onset of anaesthesia. The lidocaine/tetracaine patch provided an important alternative to lidocaine/prilocaine cream for topical local anaesthesia.
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            Topical anesthetics for dermatologic procedures: a review.

            Practitioners are increasingly using topical anesthetics to decrease the pain associated with superficial dermatologic, aesthetic, and laser procedures. Numerous lidocaine-containing products are available, but comprehensive reviews are lacking regarding their relative safety profiles and appropriate dermatologic uses. A literature review of currently available topical anesthetics, their safety profiles, and dermatologic uses was conducted. Factors that should be considered to reduce the risk of side effects associated with the use of topical anesthetics include the amount of product used, body location, size of the surface area, and duration of product application. Many case reports document adverse outcomes associated with the use of compounded products that the Food and Drug Administration has not approved that have inappropriately high anesthetic concentrations and from the use of topical anesthetics on excessively large skin surface areas during laser treatments. Lidocaine-containing products play an integral role in cutaneous anesthesia by providing patient comfort with minimal side effects. Careful attention must be paid to the particular anatomic location, the total surface area covered, and the duration of anesthetic skin contact. © 2012 by the American Society for Dermatologic Surgery, Inc. Published by Wiley Periodicals, Inc.
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              Topical anaesthesia with EMLA, a new lidocaine-prilocaine cream and the Cusum technique for detection of minimal application time.

              The minimal effective onset time of the new topical anaesthetic formulation EMLA (a eutectic mixture of lidocaine and prilocaine), was evaluated by the double-blind technique in 53 female and 66 male patients (median age 40 and 36 years, respectively) subjected to intravenous cannulation. Conventional plotting and regression analysis failed to answer the question. The Cusum technique, originally designed for industrial production control, could successfully be applied to solve the problem. It demonstrated a minimal effective EMLA application time of 45 min in adults.

                Author and article information

                J Pain Res
                J Pain Res
                Journal of Pain Research
                Journal of Pain Research
                Dove Medical Press
                10 May 2017
                : 10
                : 1105-1109
                [1 ]Department of Anesthesiology, Intensive Care, Emergency Medicine and Pain Therapy, St. Josefs-Hospital Cloppenburg, Cloppenburg
                [2 ]Clinic for Anesthesiology and Operational Intensive Care, Franziskus Hospital Bielefeld, Bielefeld
                [3 ]Clinic for Anesthesiology and Intensive Care, Medizinische Hochschule Hannover, Hannover
                [4 ]Clinic for Anesthesiology and Pain Therapy, Klinikum Bremen-Mitte, Bremen, Germany
                Author notes
                Correspondence: Christian Weilbach, Department of Anesthesiology, Intensive Care, Emergency Medicine and Pain Therapy, St. Josefs-Hospital Cloppenburg, Krankenhausstraße 13, 49661 Cloppenburg, Germany, Email christian.weilbach@ 123456kk-om.de
                © 2017 Weilbach et al. This work is published and licensed by Dove Medical Press Limited

                The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

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