Topical Anesthetic Creams

Evaluating the efficacy of local anesthetic techniques during scalp microneedling

INTRODUCTION

An increasing interest in minimally invasive procedures hassled to a demand for an effective local anesthetic algorithm. The scalp presents a challenge in achieving effective anesthesia due to the presence of hair shafts. This study aims to evaluate the efficacy of different methods during a microneedling procedure, including 25 mg lidocaine and 25 mg prilocaine cream, skin spray with 10% lidocaine, and cold gel compresses.

MATERIALS AND METHODS

Sixty-two men aged between 20 and 50 years underwent three microneedling treatments, each using a different method of anesthesia. The treatment area was divided into two equal parts, with one part exposed to a specific anesthetic method. Patients were asked to rate their pain on a 0-10 verbal analog scale. An attempt was made to objectify the results using algometry.

RESULTS

A negative correlation was observed between the algometry results and the VAS score after the application of the cream and cold compresses.

DISCUSSION

When choosing monotherapy, it is recommended to use cold gel compresses for scalp microneedling after considering the advantages and disadvantages of different methods.

Lidocaine spray vs mepivacaine local infiltration for suturing 1st/2nd grade perineal lacerations: a randomised controlled non-inferiority trial

BACKGROUND

Perineal lacerations are a very common complication of post-partum. Usually, the repair of 1st and 2nd-grade lacerations is performed after the administration of local anesthesia. Despite the great relevance of the problem, there are only a few studies about the best choice of local anesthetic to use during suturing. We performed a randomised controlled trial to evaluate the efficacy and safety of the use of a local anesthetic spray during the suturing of perineal lacerations in the post-partum.

METHODS

We compared the spray with the standard technique, which involves the infiltration of lacerated tissues, using the NRS scale. 136 eligible women who had given birth at University Hospital of Udine were enrolled and randomly assigned to receive nebulization of Lidocaine hydrochloride 10% spray (experimental group) or subcutaneous/submucosal infiltration of mepivacaine hydrochloride (control group) during suturing of perineal laceration.

RESULTS

The lacerations included 84 1st-grade perineal traumas (61.7%) and 52 2nd-grade perineal traumas (38.2%). All the procedures were successfully completed without severe complications or serious adverse reactions. There were no statistically significant differences between the two groups in terms of blood losses or total procedure time. Moreover, there were no statistically significant differences in terms of NRS to none of the intervals considered. Regarding the application of the spray in the B group, in 36 cases (52.9%) it was necessary to improve the number of puffs previously supposed to be sufficient (5 puffs). Just in 3 cases, an additional injection was necessary (4.4%).

CONCLUSIONS

Our study demonstrates that lidocaine spray alone can be used as a first line of local anesthetic during the closure of I-II-grade perineal lacerations, as it has comparable efficacy to mepivacaine infiltration.

TRIAL REGISTRATION

The trial was recorded on https://clinicaltrials.gov . Identification number: NCT05201313. First registration date: 21/01/2022. Unique Protocol ID: 0042698/P/GEN/ARCS.

Drug Permeability: From the Blood-Brain Barrier to the Peripheral Nerve Barriers

Drug delivery into the peripheral nerves and nerve roots has important implications for effective local anesthesia and treatment of peripheral neuropathies and chronic neuropathic pain. Similar to drugs that need to cross the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) to gain access to the central nervous system (CNS), drugs must cross the peripheral nerve barriers (PNB), formed by the perineurium and blood-nerve barrier (BNB) to modulate peripheral axons. Despite significant progress made to develop effective strategies to enhance BBB permeability in therapeutic drug design, efforts to enhance drug permeability and retention in peripheral nerves and nerve roots are relatively understudied. Guided by knowledge describing structural, molecular and functional similarities between restrictive neural barriers in the CNS and peripheral nervous system (PNS), we hypothesize that certain CNS drug delivery strategies are adaptable for peripheral nerve drug delivery. In this review, we describe the molecular, structural and functional similarities and differences between the BBB and PNB, summarize and compare existing CNS and peripheral nerve drug delivery strategies, and discuss the potential application of selected CNS delivery strategies to improve efficacious drug entry for peripheral nerve disorders.

Nitrous Oxide Reduces Pain Associated With Local Anesthetic Injections

BACKGROUND

Local anesthetic injections can be painful and distressing.

OBJECTIVE

The aim of this study was to determine whether nitrous oxide, ice, vibration, or topical anesthetic improves analgesia for local anesthetic injections.

METHOD

A cohort study of 400 patients undergoing Mohs micrographic surgery with local anesthetic was conducted. Patients received no intervention (n = 200), ice (n = 50), topical anesthetic cream (n = 50), vibration device (n = 50), or nitrous oxide (n = 50). Pain was rated using the Visual Analogue Scale (VAS) and Wong-Baker FACES Pain Rating Scale.

RESULTS

Without intervention, mean VAS was 4.2 and FACES was 4.6. Nitrous oxide was the most successful in reducing pain (mean VAS 1.6 vs. 4.2, P < .01, FACES 1.2 vs. 4.6, P < .01). Topical ice reduced pain (mean VAS 3.0 vs. 4.2, P < .01, FACES 3.0 vs. 4.6, P < .01). Vibration reduced pain (mean VAS 3.5 vs. 4.2, P < .01, FACES 3.6 vs. 4.6, P < .01). Higher pain scores were associated with age <50 (P = .02), male sex (P = .05), and surgery on the nose, lip, ear, or eyelid (P = .02).

CONCLUSION

Nitrous oxide, ice, and vibration reduce injection pain. These interventions are especially useful for younger males undergoing surgery on the nose, lip, ear, or eyelid.

Lidocaine-prilocaine cream versus local infiltration anesthesia in pain relief during repair of perineal trauma after vaginal delivery: a systematic review and meta-analysis

Background: Perineal trauma is a common problem that may affect women during vaginal delivery; this trauma can be either spontaneous (tear) or intentional (episiotomy). When repair of perineal trauma is required, adequate analgesics must be obtained. Topical products as lidocaine-prilocaine (EMLA) cream is one of the suggested methods, but still there is lack of evidence with regard to its efficacy and safety.Objective: The aim of this review is to assess the evidence of utilizing EMLA cream in comparison to local perineal infiltration anesthesia for pain control during perineal repair after vaginal delivery.Data sources: Medline, Embase, Dynamed Plus, ScienceDirect, TRIP database, ClinicalTrials.gov and the Cochrane Library were searched electronically from January 2006 to May 2018 for studies investigating the effect of lidocaine-prilocaine cream in relieving pain during repair of perineal trauma.Methods of study selection: All randomized controlled trials assessing effect of lidocaine-prilocaine cream versus local infiltration anesthesia in relieving pain during repair of perineal trauma were considered for this meta-analysis. Fifteen studies were identified of which four studies deemed eligible for this review. Quality and risk of bias assessment was performed for all studies.Data extraction: Two researchers independently extracted the data from the individual articles and entered into RevMan software. The weighted mean difference (WMD) and 95% confidence interval (CI) was calculated. Statistical heterogeneity between studies was assessed by the Higgins chi-square and (I²) statistics. When heterogeneity was significant, a random-effects model was used for meta-analysis. Otherwise, the fixed effect meta-analysis was used when there was no significant heterogeneity.Results: Pooled analysis of result in "pain score" was insignificant between the two groups (WMD -1.11; 95% CI (-2.55 to 0.33); p = .13). Furthermore, the use of additional analgesia showed no statistically significant difference between the two groups (WMD 1.34; 95% CI (0.66-2.71), p = .42). Regarding patient satisfaction, an overall analysis of three studies showed significant results favoring EMLA cream group users (WMD 4.65; 95% CI (1.96-11.03), p = .0005). The pooled analysis of the outcome "duration of repair" showed the significantly shorter duration of repair in EMLA cream users (n = 92) than local infiltration anesthesia (n = 95) (1.72 min; 95% CI (-2.76 to -0.67), p = .001).Conclusions: This meta-analysis suggests that topical lidocaine-prilocaine cream gives comparable results in reducing pain during perineal repair after vaginal delivery.

Comparison of Emla cream and lidocaine injection for local anaesthetic before radiofrequency reduction of the inferior turbinates

We compared the effectiveness of local anaesthetic with Emla cream with that of an injection of lidocaine for radiofrequency reduction of the inferior turbinates. We studied 98 consecutive patients with hypertrophied inferior turbinates, 46 of whom were given Emla cream and 52 lidocaine injection. The procedure began five minutes after the injection of lidocaine and 10minutes after the Emla cream had been applied. Patients were asked to indicate on a visual analogue scale (VAS) the degree of perioperative pain, anxiety, sensation of choking, and discomfort on swallowing that they felt after the procedure. Patients treated with Emla had significantly lower VAS scores for discomfort on swallowing than those treated with lidocaine (p=0.001), but there were no other significant differences between the two groups. We conclude that Emla cream is an efficacious alternative to infiltration of lidocaine for radiofrequency reduction of the inferior turbinates.

A Review of Local Anesthetics: Minimizing Risk and Side Effects in Cutaneous Surgery

BACKGROUND

The specialty of dermatology relies heavily on local anesthesia for diagnosis and management of skin disease. The appropriate selection, preparation, administration, and monitoring of these medications affect surgical outcome and patient safety and satisfaction.

OBJECTIVE

To perform a comprehensive literature review of the side effects and risks associated with local anesthetics used in cutaneous surgery. Current recommendations to reduce risk and minimize side effects are reviewed.

MATERIALS AND METHODS

A comprehensive review of the English-language medical literature search was performed.

RESULTS

No current review articles of the side effects and risks of local anesthetics were identified. This review serves to discuss local anesthetics commonly used in dermatology and cutaneous surgery along with practical information regarding prevention of adverse outcomes and addressing local and systemic reactions when they arise.

CONCLUSION

Local anesthetics commonly used in cutaneous surgery have potential risks and side effects. Appropriate selection and utilization of local anesthetics and knowledge of the means to prevent and address these risks can impact surgical outcomes, patient satisfaction and safety, and ultimately patient experience in the dermatology clinic.

Comparison of lidocaine/tetracaine cream and lidocaine/prilocaine cream for local anaesthesia during laser treatment of acne keloidalis nuchae and tattoo removal: results of two randomized controlled trials

BACKGROUND

Pain is a common adverse effect of dermatological laser procedures. Currently, no standard topical anaesthetic cream exists for deeper dermal laser procedures.

OBJECTIVES

To compare the efficacy of lidocaine/tetracaine cream and lidocaine/prilocaine cream in reducing self-reported pain during deeper dermal laser treatment of acne keloidalis nuchae (AKN) and tattoos.

METHODS

We conducted two randomized, double-blind, controlled clinical trials with intrapatient, split-lesion designs: study A included patients with AKN (n = 15); study B included patients with black tattoos (n = 15). The primary end point was the patients' self-reported pain on a 10-cm visual analogue scale (VAS). Secondary objectives were the percentage of patients with adequate pain relief, willingness to pay €25 for the cream that provided the best pain relief and safety of the creams.

RESULTS

In both studies, VAS scores were lower for lidocaine/prilocaine cream, with a mean VAS difference in study A of 1·9 [95% confidence interval (CI) 1·0-2·8] and in study B of 0·6 (95% CI -0·7 to 1·9). In study A, adequate pain relief was achieved in 13% (n = 2) with lidocaine/tetracaine cream vs. 73% (n = 11) with lidocaine/prilocaine cream (P = 0·004), and in study B in 53% (n = 8) vs. 80% (n = 12), respectively (P = 0·289). In study A, 47% (n = 7) were willing to pay an additional €25 vs. 73% (n = 11) in study B. No serious adverse events occurred.

CONCLUSIONS

Lidocaine/prilocaine cream under plastic occlusion is the preferred topical anaesthetic during painful laser procedures targeting dermal chromophores.

Effects of two different local anaesthetic methods vs no anaesthesia on pain scores for intratympanic injections

OBJECTIVE

This study compared the pain associated with the intratympanic injection combined with various local anaesthetics vs without anaesthesia.

METHODS

The study included 40 patients (aged 18-78 years) who received intratympanic steroid injections for sudden idiopathic hearing loss or tinnitus. Each patient underwent all three injection methods at one-week intervals. Patients received one of two local anaesthetics (lidocaine injection or lidocaine spray) or no anaesthesia before intratympanic injection, and used a visual analogue scale to indicate the pain level after 5 and 45 minutes.

RESULTS

Five minutes after injection, patients who did not receive anaesthesia and those who received lidocaine spray reported lower pain scores than those who received a lidocaine injection (p < 0.05). There was no difference in pain scores for all three methods at 45 minutes after intratympanic injection.

CONCLUSION

Neither of the local anaesthetics was found to be superior to having no anaesthesia.

The efficacy of eutectic mixture of local anesthetics as a topical anesthetic agent used for dental procedures: A brief review

Dental pain management is one of the most critical aspects of modern dentistry which might affect patient's quality of life. Several methods are suggested to provide a painless situation for patients. Desensitization of the oral site using topical anesthetics is one of those methods. The improvements of topical anesthetic agents are probably one of the most important advances in dental science in the past 100 years. Most of them are safe and can be applied on oral mucosa with minimal irritation and allergic reactions. At present, these agents are various with different potent and indications. Eutectic mixture of local anesthetics (EMLA) (lidocaine + prilocaine) is a commercial anesthetic agent which has got acceptance among dental clinicians. This article provides a brief review about the efficacy of EMLA as a topical anesthetic agent when used during dental procedures.

Topical anaesthetic effects on skin vasculature with potential implications for laser treatment

Laser treatment of vascular lesions is affected by parameters including the diameter and depth of the vessels and flow within the vessels. Topical anaesthetics are in common use prior to laser treatment but may have effects on vessel parameters and, subsequently, the efficacy of laser treatment. Eleven patients with capillary vascular malformations were investigated for vessel diameter before and after elective application of a topical anaesthetic, Eutectic Mixture of Local Anaesthetics (EMLA) (AstraZeneca) or Ametop (S&N Health), prior to pulsed dye laser treatment. EMLA contains 2.5% lidocaine ad 2.5% prilocaine, and Ametop gel contains 4% tetracaine. Patients' capillary malformations were assessed using confocal laser scanning microscopy (CLSM) (Vivascope 1500 Mavig GmbH, Munich). Six of the 11 patients recruited had EMLA topical anaesthetic, and five had Ametop. Four hundred twenty-one diameters were measured. The mean vessel diameter was 50.87 μm. Previous laser treatments undergone by each patient were noted to exclude this as a confounding variable, and no significant difference was found between topical anaesthetic groups. Statistical calculations were made using GenStat and Minitab. There is no evidence that Ametop affects mean diameter (p value is 0.361). EMLA reduces the mean diameter of vessels (p = 0.002), with a 27% reduction in post-EMLA diameter. This study demonstrates that the use of EMLA cream has a statistically significant reduction vessel diameter. As it is known that vessel diameter is important for the response of laser treatment, the use of EMLA may affect outcome.

The use of eutectic mixture of lidocaine and prilocaine in mice (Mus musculus) for tail vein injections

OBJECTIVE

To investigate a topical local anesthesia technique as a means to prevent and/or diminish pain in mice in a laboratory setting associated with tail vein injections performed by personnel in training.

STUDY DESIGN

Prospective, randomized experimental trial.

ANIMALS

Thirty six adult female, 23-28 g CD-1 mice from an in-house training colony. They were acclimated to routine training and handling classes.

METHODS

Eutectic mixture of local anesthetics (EMLA) cream (2.5% lidocaine/2.5% prilocaine) or a bland ointment control (n = 18) was applied on the tail prior to intravenous injection. The injections were performed by novices, who had never attempted the procedure, and experienced personnel. All participants were blinded to treatment groups. Three injection attempts were allowed per animal. The mice were observed and scored by blinded evaluators for behavioral and physiological changes, including respiratory rate, vocalization, tail flick, and escape behaviors, during and after the injection.

RESULTS

This study demonstrates that aversive behaviors induced by lateral tail vein injection were not changed by the preemptive application of EMLA cream. The aversive behaviors associated with lateral tail vein injection were significantly affected by the number of injection attempts and the individual's experience level.

CONCLUSIONS AND CLINICAL RELEVANCE

Topical EMLA cream did not reduce signs of aversive reaction to tail vein injection and thus we did not find support for its use in mouse training programs for tail vein injections.

EMLA(®) cream as local anesthetic for radiofrequency turbinate tissue reduction

Radiofrequency volumetric tissue reduction is a minimally invasive technique in the treatment of turbinate hypertrophy and is generally performed under local anesthesia. However, perioperative discomfort and pain are common side effects and studies concerning the technique of choice to anesthetize the nasal mucosa in this procedure are lacking. The aim of this prospective controlled trial is to assess the effectiveness of EMLA(®) cream as a topical anesthetic for radiofrequency volumetric tissue reduction of inferior turbinates comparing its effect with that obtained using a traditional anesthetic technique. 200 consecutive patients undergoing volumetric tissue reduction with topical anesthesia were enrolled. Patients were divided into two groups: Group A included 100 patients treated by placing cotton pledgets soaked with lidocaine 10% in the inferior meatus followed by the injection of 2% lidocaine into the head of the inferior turbinate; Group B included 100 patients treated with EMLA(®) cream. Patients were evaluated before and after surgery using rhinomanometry for obstructive symptoms. Four VAS about pain, troublesome swallowing, choking sensation and intraoperative anxiety were submitted to each patient immediately after surgery and after 2 months to assess various aspects of perioperative discomfort. A significant increase of nasal airflow was observed without differences between the two groups. Subjective evaluation regarding perioperative discomfort showed significant differences between Groups A and B immediately after surgery although it was less pronounced 2 months later. The results of this study suggest that EMLA(®) cream is an efficient tool in obtaining an adequate anesthetic effect in this procedure.

Comparison of cooling and EMLA to reduce the burning pain during capsaicin 8% patch application: a randomized, double-blind, placebo-controlled study

Topical capsaicin 8% was developed for the treatment of peripheral neuropathic pain. The pain reduction is associated with a reversible reduction of epidermal nerve fiber density (ENFD). During its application, topical capsaicin 8% provokes distinct pain. In a randomized, double-blind study analyzed with a block factorial analysis of variance, we tested whether cooling the skin would result in reliable prevention of the application pain without inhibiting reduction of ENFD. A capsaicin 8% patch was cut into 4 quarters and 2 each were applied for 1 hour on the anterior thighs of 12 healthy volunteers. A randomization scheme provided for 1 of the application sites of each thigh to be pretreated with EMLA and the other with placebo, whereas both application sites of 1 thigh, also randomly selected, were cooled by cool packs, resulting in a site temperature of 20°C during the entire treatment period. The maximum pain level given for the cooled sites (visual analogue scale [VAS] 1.3 ± 1.4) proved to be significantly lower than for the non-cooled sites (VAS 7.5 ± 1.9) (P < .0001). In contrast, there was no significant difference in application pain between the sites pretreated with EMLA or with placebo (VAS 4.1 ± 3.6 vs 4.8 ± 3.5, P = .1084). At all application sites, ENFD was significantly reduced by 8.0 ± 2.8 (ENF/mm ± SD, P < .0001), that is, 70%, with no significant differences between the sites with the different experimental conditions. In conclusion, cooling the skin to 20°C reliably prevents the pain from capsaicin 8% patch application, whereas EMLA does not. ENFD reduction is not inhibited by cooling.

Review of lidocaine/tetracaine cream as a topical anesthetic for dermatologic laser procedures

There are multiple different topical anesthetic options available to minimize the pain associated with cosmetic dermatologic procedures. These options, either alone or in combination, have diverse profiles for effectiveness, ease of use, application time, need for occlusion, and side effects. The lidocaine/tetracaine cream (Pliaglis(®), Galderma Laboratories, Texas, USA), one of the newer combination options, offers effective pain alleviation that has been evaluated in numerous clinical trials. This combination anesthetic is associated with a very favorable profile because of its ease of use and mild side effects compared to other topical local anesthetics. An overview of available topical local anesthetics will be provided with an outline of clinical study characteristics and results regarding the use of lidocaine/tetracaine cream.

The efficacy and safety of topical EMLA cream application for minor surgery of the adult penis

Background and Objectives:

A variety of surgical procedures of the penis can be performed under local anesthesia. We evaluated the efficacy and safety of EMLA cream anesthetic in such procedures.

Materials and Methods:

In total 330 adult patients were subjected to minor penile surgery including: Complete circumcision (73), short frenulum plasty (168), meatotomy (14), fulguration of penile warts (56) and fulguration of urethral (meatal) warts (19). The level of anesthesia obtained by EMLA cream application along with any adverse effects was recorded.

Results:

The use of EMLA on mucosal lesions provided excellent level of local anesthesia in almost all patients (245/246, 99.5%). Anesthesia of skin lesions was in part influenced by the site of application. Circumcision patients showed the lowest efficacy of the EMLA cream as the majority (~80%) required some form of further anesthesia until the completion of the procedure. No significant adverse effects were noted. A transient erythema was present in almost all mucosal applications.

Conclusions:

The topical anesthetic EMLA cream is a useful, efficient and safe tool for minor surgical procedures of the penis at the office setting, with the exception of circumcision, where an additional type of anesthesia is likely to be necessary. Side effects can be kept to a minimum when the suggested doses are respected (especially at mucosal application) and the time allowed for action is carefully tailored to the site of application and the type of procedure.

Efficacy and safety of a lidocaine/tetracaine medicated patch or peel for dermatologic procedures: a meta-analysis

Background

To justify the use of the lidocaine/tetracaine medicated patch or peel as a preventive treatment for reducing pain and discomfort in adults and children. We reviewed randomized controlled trials (RCTs) to evaluate the efficacy and safety of the lidocaine/tetracaine medicated patch or peel compared with placebo.

Methods

Ten RCTs (574 patients) were included in this systemic review. Relevant studies were identified through searches of MEDLINE, SCOPUS and the Cochrane database library. The outcome was the adequacy of cutaneous anesthesia reflected in the patient's assessment of pain intensity during minor dermatologic procedures and adverse effects after application of the lidocaine/tetracaine medicated patch or peel versus placebo.

Results

The efficacy of the lidocaine/tetracaine patch or peel was consistently very significantly beneficial 30 or 60 minutes after the application compared to placebo (Relative risk, RR: 2.5; Number needed to treat, NNT: 2.2). We did not identify any difference in the effectiveness of adequate analgesia between the lidocaine/tetracaine patch and peel (the number needed to treat or to harm, NNT 2.4 vs. 2.0). No serious side effects or adverse events were observed with the lidocaine/tetracaine medicated patch or peel and placebo. Minor skin reactions were transient and resolved without treatment (Odd ratio, OR: 1.4 and 95% confidence interval, CI: 0.9-2.1; NNT: 14.9).

Conclusions

The lidocaine/tetracaine medicated patch or peel is a well accepted, effective and safe method for minor dermatologic procedures based on pooled data of trials in terms of adequacy of cutaneous anesthesia and adverse effects.

Evaluation of pain associated with facial injections using CoolSkin in rhytidectomy

PURPOSE

To evaluate the use of the CoolSkin(®) (Elbio, Seoul, Korea) skin-cooling device to reduce injection pain during rhytidectomy.

METHOD

Nineteen patients underwent rhytidectomy using the CoolSkin at -4°C on the first side lateral injection. The second side was then started without the cooling. Patients were offered cooling if they desired it on the second side. Surveys were administered 24 hours after the procedure, comparing pain (scale 0-5) and investigating treatment preferences. Patient healing was tracked for 6 weeks.

RESULTS

Mean pain score for the untreated side was 4.63 versus 2.37 for the CoolSkin-treated side (P < 0.001). All patients asked for the second side to be cooled, and 89% were in favor of the chilling procedure when surveyed 24 hours afterwards. Sixty eight percent of patients stated that this device reduced fear of future injections. No flap loss or healing sequelae were noted from device use.

CONCLUSION

The CoolSkin device is an effective tool to reduce injection pain laterally during rhytidectomy.

Effect of 4% topical lidocaine applied to the face on the serum levels of lidocaine and its metabolite, monoethylglycinexylidide

BACKGROUND

Topical lidocaine is a common form of anesthesia for a wealth of procedures across a large number of disciplines, including laser treatments. Preparations can be purchased over the counter with no prescription necessary. It is considered a safer and more acceptable form of anesthetic than hypodermic injections; however, there have been reports of fatalities following its application. Above certain serum lidocaine concentrations, patients may experience effects of toxicity such as lightheadedness and paraesthesia; these effects can progress to seizures and cardiorespiratory depression, which can ultimately lead to death. The active metabolite of lidocaine, monoethylglycinexylidide (MEGX), can be almost as potent as lidocaine in terms of toxicity.

OBJECTIVES

The authors examine the levels of both lidocaine and MEGX in blood serum after application of topical lidocaine.

METHODS

Twenty-five healthy volunteers were assigned to one of four groups (A, B, C, D). Group A had 2.5 g of 4% lidocaine topical anesthetic cream applied to the face for one hour without occlusion, Group B had 5 g applied to the face for one half-hour without occlusion, Group C had 5 g applied to the face for one hour without occlusion, and Group D had 5 g applied to the face for one hour with occlusion. To evaluate serum concentrations, blood was drawn every 30 minutes for four hours.

RESULTS

Group D showed the highest serum levels of lidocaine and MEGX, a three-fold increase compared with group C, which received the same dose (5g topical 4% lidocaine) but without occlusion. In group D, peak serum levels occurred at 90 minutes for serum lidocaine, which was also the fastest of the four groups. Serum MEGX levels peaked much later than serum lidocaine levels, at 210 minutes. Individual serum levels did not exceed 0.6 µg/mL. Across the groups, there was significant interindividual variation in both lidocaine and MEGX serum levels (P = .061). Applications of 5 g of 4% lidocaine resulted in higher serum concentration of both lidocaine and MEGX. When comparing group A to group C, doubling the dose of 4% lidocaine from 2.5 g to 5 g resulted in double the serum levels of MEGX and a 50% increase in the serum lidocaine levels (P = .021). When comparing groups C and D, the addition of an occlusive dressing resulted in a tripling of the serum lidocaine levels and a doubling of the serum MEGX levels, both of which were statistically significant (P < .001). When comparing all four groups, there were significant differences between the combined serum concentrations of lidocaine and MEGX (P < .001).

CONCLUSIONS

Topical lidocaine preparations are increasingly being employed to provide a patient-friendly form of noninvasive analgesia for a multitude of procedures. Some preparations are available over the counter for unsupervised patient application. Our study has demonstrated significant interindividual variability for a given dose, especially when occlusion is applied. There have been fatalities resulting from topical lidocaine application, and our study suggests that this is the result of the unpredictability of lidocaine metabolism between individuals. Therefore, we recommend that caution be exercised with topical lidocaine preparations, in particular when applied in conjunction with occlusive dressings.

Local anesthesia in dermatology

Local and regional anesthetic procedures are an integral part of daily dermatological practice. Safe and effective analgesia in skin and soft tissues is crucial for otherwise painful diagnostic or therapeutic interventions. Tumescent local anesthesia allows for pain-free interventions that previously had to be done by using general anesthesia. Older patients with multiple co-morbidities are especially suited for local anesthetic procedures, because they may significantly reduce surgical risks. For dermatologists, the knowledge of mode of action and toxicity of local anesthetics, as well as the emergency management of their potential complications, is essential.

Local anesthetics: uses and toxicities

Surgeons are asked to do more and larger procedures as outpatient procedures as the economics of medicine evolve. Indeed, we all carry out procedures on an outpatient basis that only a short time ago we would consider only on an inpatient basis. Further, procedures that had previously been performed under a general anesthetic are now being performed under local anesthesia. A good working knowledge of local anesthetics (LAs) will better enable the surgeon to meet those demands and to do so in a way that will enhance the patient's safety, experience, and comfort. Although the focus of this issue of Clinics is minor surgery, any meaningful discussion of LAs has to go a little further than a 3-mL syringe and a small amount of lidocaine.

Comparison between lidocaine-prilocaine cream (EMLA) and mepivacaine infiltration for pain relief during perineal repair after childbirth: a randomized trial

OBJECTIVE

The purpose of this study was to compare the effectiveness of topically applied lidocaine-prilocaine (EMLA) cream with local anesthetic infiltration in the reduction of pain during perineal suturing after childbirth.

STUDY DESIGN

Sixty-one women with either an episiotomy or a perineal laceration after vaginal delivery were assigned randomly to receive either the application of EMLA cream (n = 31) or infiltration with mepivacaine (n = 30) before perineal suturing. Primary outcome was pain during perineal repair.

RESULTS

Women in the EMLA group had lower pain scores than those in the mepivacaine group (1.7 +/- 2.4 vs 3.9 +/- 2.4; P = .0002). The proportion of women who needed additional anesthesia was similar in the 2 groups (3/30 vs 5/31; P = .71). A significantly higher proportion of women expressed satisfaction with anesthesia method in the EMLA group, compared with the mepivacaine group (83.8% vs 53.3%; P = .01)

CONCLUSION

EMLA cream appears to be an effective and satisfactory alternative to local anesthetic infiltration for the relief of pain during perineal repair.