Transdermal analgesia with local anesthetics in children: review, update and future directions

Novel Therapeutic Hybrid Systems Using Hydrogels and Nanotechnology: A Focus on Nanoemulgels for the Treatment of Skin Diseases

Topical and transdermal drug delivery are advantageous administration routes, especially when treating diseases and conditions with a skin etiology. Nevertheless, conventional dosage forms often lead to low therapeutic efficacy, safety issues, and patient noncompliance. To tackle these issues, novel topical and transdermal platforms involving nanotechnology have been developed. This review focuses on the latest advances regarding the development of nanoemulgels for skin application, encapsulating a wide variety of molecules, including already marketed drugs (miconazole, ketoconazole, fusidic acid, imiquimod, meloxicam), repurposed marketed drugs (atorvastatin, omeprazole, leflunomide), natural-derived compounds (eucalyptol, naringenin, thymoquinone, curcumin, chrysin, brucine, capsaicin), and other synthetic molecules (ebselen, tocotrienols, retinyl palmitate), for wound healing, skin and skin appendage infections, skin inflammatory diseases, skin cancer, neuropathy, or anti-aging purposes. Developed formulations revealed adequate droplet size, PDI, viscosity, spreadability, pH, stability, drug release, and drug permeation and/or retention capacity, having more advantageous characteristics than current marketed formulations. In vitro and/or in vivo studies established the safety and efficacy of the developed formulations, confirming their therapeutic potential, and making them promising platforms for the replacement of current therapies, or as possible adjuvant treatments, which might someday effectively reach the market to help fight highly incident skin or systemic diseases and conditions.

Transdermal drug delivery system of lidocaine hydrochloride based on dissolving gelatin/sodium carboxymethylcellulose microneedles

In this study, it was aimed to introduce a transdermal drug delivery system with dissolving microneedles (DMNs) based on gelatin (GEL) and sodium carboxymethyl cellulose (NaCMC) for lidocaine hydrochloride (LidoHCl) delivery. Different ratios of GEL and NaCMC were mixed, loaded with an active agent of LidoHCl, and treated with glutaraldehyde (GTA) as a crosslinker agent. Prepared hydrogels were cast into a silicon mold. Hereby, microneedles (MNs) with 500 µm height, 35° needle angle, 40-µm tip radius, and 960-µm tip-to-tip distance were fabricated. Samples containing LidoHCl 40%, GEL/NaCMC 5:1 (wt/wt), and polymer/GTA ratio 3.1 (wt/wt) showed the highest drug release ability (t < 10 min) with proper mechanical properties in comparison with other samples. Due to the drug release in a short time (fewer than 10 min), this drug delivery system can be used for rapid local anesthesia for pain relief as well as before minor skin surgeries.

Graphical Abstract

Transdermal Maltose-Based Microneedle Patch as Adjunct to Enhance Topical Anesthetic before Intravenous Cannulation of Pediatric Thalassemic Patients Receiving Blood Transfusion: A Randomized Controlled Trial Protocol

Intravenous cannulation is experientially traumatic to children. To minimize this, EMLA^® is applied on the would-be-cannulated area before IV cannula insertion. However, the time to achieve its maximum efficacy may be affected due to incomplete cutaneous absorption and the duration of application. The latter may be a limiting factor in a busy healthcare facility. The usage of dissolvable maltose microneedles may circumvent this problem by introducing micropores that will facilitate EMLA^® absorption. A randomized phase II cross-over trial will be conducted to compare the Visual Analogue Scale (VAS) pain scores and skin conductance algesimeter index between 4 different interventions (1 fingertip unit (FTU) of EMLA^® with microneedle patch for 30 min before cannulation; 0.5 FTU of EMLA^® with microneedle patch for 30 min; 1 FTU of EMLA^® with microneedle for 15 min; 1 FTU of EMLA^® with sham patch for 30 min). A total of 26 pediatric patients with thalassemia aged between 6 and 18 years old and requiring blood transfusion will be recruited in this trial. During the visits, the VAS scores and skin conductance algesimeter index at venous cannulation will be obtained using the VAS rulers and PainMonitor™ machine, respectively. The trial will commence in August 2021 and is anticipated to end by August 2022.

Intradermal injection of lidocaine with a microneedle device to provide rapid local anaesthesia for peripheral intravenous cannulation: A randomised open-label placebo-controlled clinical trial

Background

Peripheral venous cannulation is one of the most common procedures in medicine. It is associated with noticeable pain and apprehension, although in most cases it is performed without any anesthesia due to lack of a painless, cost-effective option, which would provide rapid local anesthesia with subsequent significant reduction in the experienced pain. We conducted an open-label placebo-controlled clinical trial to evaluate the efficacy and safety of a 2% lidocaine injection using the commercially available microneedle device MinronJet600 (NanoPass Technologies Ltd, Israel) to achieve rapid local anesthesia prior to peripheral venous cannulation.

Methods

One hundred and two subjects were randomly allocated into two groups. In the first group, 100μL of lidocaine hydrochloride (2%) was injected intradermally to subjects using the MicronJet600 device in the left arm (MJ-Lido) and 100μL of saline was injected intradermally using the device in the right arm (MJ-Saline). In the second group, 100μL of lidocaine hydrochloride (2%) was injected using the MicronJet600 device into the left arm (MJ-Lido), with no injection into the right arm of subjects (No pretreatment). In both groups the intradermal injection was performed at the cannulation site prior to insertion of a 18G cannula into a median cubital vein in both arms. As a primary variable, a score of cannulation-induced pain was indicated by subjects using a 100-point visual analog scale immediately after cannulation. As a secondary variable, subjects in Group 2 also indicated their preference to receive the anaesthetic injection with MicronJet600 in the future by using the 5-point Likert scale. Also, as a secondary variable, the duration of skin numbness after lidocaine injection was indicated by performing a superficial pin-prick with a 27G needle at 15, 30 and 45 minutes, at distances of 1, 2 and 3 centimeters from the injection site.

Results

A significant pain reduction (11.0-fold) was achieved due to the lidocaine injection compared to the cannulation without any pretreatment (p< 0.005). After the lidocaine injection the anesthesia was effective up to 2 centimeters from the injection site and remained for up to 30 minutes. Eighty percent of subjects from the second group preferred cannulation after the lidocaine injection over cannulation without any pretreatment. No significant side effects were identified.

Conclusion

Intradermal injection of anaesthetic with Micronjet600 was found to be a safe and effective option for providing rapid local anesthesia for peripheral intravenous cannulation.

Trial regiatration

The clinical trial was registered, before the patient enrollment began, in the Research Registry publicly accessible database (registration identifier: researchregistry4662). Also, the trial was registered in ClinicalTrials.gov (registration identifier: NCT05108714) after its completion.

Optimization of Influential Variables in the Development of Buprenorphine and Bupivacaine Loaded Invasome for Dermal Delivery

Purpose: Hydrophilic drugs are extensively applied in clinical applications. Inadequate dermal penetration of these drugs is a great challenge. Incorporation of drugs into nano-carrier systems overcomes lower penetration drawbacks. Invasomes are novel nano-carrier systems which enhance transdermal penetration by using terpene and ethanol in their structures. buprenorphine and bupivacaine hydrochlorides are two potent analgesic drugs that are loaded simultaneously in the nano-invasome structure as opioid and non-opioid drugs.

Methods: The full factorial experimental design was used for planning and estimating optimum formulations of invasome systems. Three influential factors like terpene type, terpene concentration and preparation method were comprehensively analyzed for achieving high encapsulation efficiency (EE) and optimum size.

Results: The mean sizes of designed invasomes were in the range of 0.39-5.86 µm and high values of EE and loading capacity (LC) were reported as 98.77 and 19.75 for buprenorphine-loaded invasome, respectively. Zeta potential measurements confirmed that the obtained high value of EE might be as a result of reversible ionic interactions between positively charged drugs and negatively charged phospholipidic part of invasome structure. Another characterization of the prepared formulations was carried out by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and dynamic light scattering (DLS) technique.

Conclusion: The satisfactory obtained results of formulations encourage researchers to get optimum topical analgesic formulations with potent and rapid onset time properties required in invasive cutaneous procedures.

QbD-Based Investigation of Dermal Semisolid in situ Film-Forming Systems for Local Anaesthesia

PURPOSE

The aim of our research work was to develop dermally applicable, lidocaine hydrochloride (LID-HCl)-containing semisolid in situ film-forming systems (FFSs) using the Quality by Design (QbD) approach to increase drug permeation into the skin.

METHODS

Silicones were used to improve the properties of formulations and to increase the permeation through the skin. The QbD approach was applied to ensure quality-based development. With initial risk assessment, the critical material attributes (CMAs) and the critical process parameters (CPPs) were identified to ensure the required critical quality attributes (CQAs).

RESULTS

During the initial risk assessment, four high-risk CQAs, namely in vitro drug release, in vitro drug permeation, drying properties, and mechanical properties, and three medium-risk CQAs, namely pH, viscosity, and film appearance were identified and investigated. Moreover, four high-risk CMAs were also considered during the formulation: permeation enhancing excipients, drying excipients, film-forming excipients, and emollients. During the experiments, LID-HCl influenced these critical parameters highly, thereby reducing the drying time. The formulation containing 25% silicone showed the best mechanical properties (49 mN skin adhesion, 20.3% film flexibility, 1.27 N film burst strength), which could predict better patient adherence. In addition, in vitro permeation studies showed that formulation containing 50% silicone has the fastest permeation rate. The flux of diffused API was 6.763 µg/cm2/h, which is much higher compared to the silicone-free formulation (1.5734 µg/cm2/h), and it can already be observed in the lower part of the dermis in 0.5 hour.

CONCLUSION

Our results show that LID-HCl has great influence on the critical parameters of FFSs. The silicone content can improve the applicability of formulations and has a favorable effect on the permeation rate of LID-HCl into the skin.

Investigation of the transdermal transport of charged local anesthetics in the presence of triterpene saponin glycosides

Percutaneous absorption and transdermal delivery of water-soluble drugs have proven to be challenging due to their low permeability through skin. Avicins which are triterpene saponin glycosides (TSGs) derived from the desert plant Acacia victoriae have not been investigated to date as chemical penetration enhancers due to their higher molecular weight (MW 2,000 Da). It was recently shown that avicins exhibit remarkable mobility across skin lipids in spite of their large size due to their unique chemical structure. In this study, the permeation of local anesthetics, lidocaine-HCl, prilocaine-HCl, and bupivacaine-HCL from aqueous vehicle, across full-thickness porcine skin was investigated in the presence of F094-a mixture of avicins. F094 was capable of enhancing the permeability of all three anesthetics from aqueous formulations at extremely low concentrations ranging from 0.1 to 1 % w/v. The enhancement, which ranged from 2- to 5-fold, was surprisingly independent of molecular weight of the anesthetics and showed clear correlation with aqueous phase solubility of the anesthetics. Since F094 was found to have no impact on the octanol/water partition coefficients of the anesthetics, this suggests that TSGs like avicins most likely impact the aqueous pathways (pericellular/pores within lipids) and as such represent an alternative means of enhancing the transdermal transport of charged drugs from water-based formulations.

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.

Rapid local anesthesia in humans using minimally invasive microneedles

OBJECTIVE

This study tested the hypothesis that minimally invasive microneedles cause less pain during injection of lidocaine, but induce local anesthesia in humans with the same rapid onset and efficacy as intradermal lidocaine injection using hypodermic needles.

METHODS

This study was a randomized, single-blinded, within participants, controlled design. Hollow, 500-μm long microneedles were used to inject lidocaine to the forearm of 15 human participants. The associated pain was recorded using a visual analog (VAS) scale. The area and depth of numbness were determined at 0, 7.5, and 15 minutes after injection. Lidocaine was also injected to the dorsum of the hand near a vein, followed by placement of an intravenous catheter and measurement of associated pain. A 26-gauge intradermal bevel hypodermic needle similarly administered lidocaine on the opposite forearm/hand to serve as the positive control.

RESULTS

VAS pain scores revealed that injection using microneedles was significantly less painful than hypodermic needles for both the forearm and dorsum of the hand injections. However, there was no significant difference in the area or depth of the resulting numbness between the 2 treatment methods at any time point (0, 7.5, and 15 min) indicating that microneedles had immediate onset and were as effective as hypodermic needles in inducing dermal anesthesia. Moreover, insertion of an intravenous catheter immediately after lidocaine injection on the dorsum of the hand led to comparable pain scores for the microneedle and hypodermic needle treated sites, further confirming efficacy of microneedles in inducing rapid local anesthesia. Lastly, 77% of the participants preferred microneedles and 80% indicated that they did not consider microneedles to be painful.

DISCUSSION

This study demonstrates for the first time that microneedle-based lidocaine injection is as rapid and as effective as hypodermic injection in inducing local anesthesia while resulting in significantly less pain during injection.

Topical preparations for pain relief: efficacy and patient adherence

There has been an increasing focus on development of new routes of drug administration to provide tailored treatments for patients, without decreasing efficacy of analgesia, in proportion to the progression of the knowledge of pain mechanisms. While acute pain acts as an alarm, chronic pain is a syndrome requiring meticulous selection of analgesic drugs of high bioavailability for long-term use. Such criteria are challenges that topical medications aim to overcome, allowing progressive delivery of active component, maintaining stable plasma levels, with a good safety profile. This review presents recent findings regarding topical formulations of the most widely used drugs for pain treatment, such as nonsteroidal anti-inflammatory agents, anesthetics, and capsaicin, and the role of physical agents as delivery enhancers (phonophoresis and iontophoresis). Although the number of topical agents is limited for use in peripheral conditions, increasing evidence supports the efficacy of these preparations in blocking nociceptive and neuropathic pain. Patient adherence to medical treatment is also a challenge, especially in chronic painful conditions. It is known that reduction of treatment complexity and pill burden are good strategies to increase patient compliance, as discussed here. However, the role of topical presentations, when compared to traditional routes, has not yet been fully explored and thus remains unclear.

Contribution of a heating element to topical anesthesia patch efficacy prior to vascular access: results from two randomized, double-blind studies

CONTEXT

Pain associated with superficial procedures, including intravenous (IV) access procedures, should be prevented when possible, especially in children.

OBJECTIVES

To evaluate a topical local anesthetic patch containing lidocaine 70 mg/tetracaine 70 mg with a heating element designed to warm the skin and facilitate rapid delivery of local anesthetics into the skin. The pilot study was designed to provide data to inform the design of the definitive study to evaluate the impact of controlled heat on the efficacy of the lidocaine/tetracaine patch (patch) when applied before IV cannulation.

METHODS

Subjects in the pilot study were randomized to eight groups that varied by heated vs. unheated patch, 20 vs. 30 minute application, and 16 vs. 18 G catheter. Subjects in the definitive study were randomized in a double-blind manner to receive either the heated or unheated patch, 20 minutes before vascular access, using a 16 G catheter in the antecubital space of the arm. In both studies, the primary efficacy measure was subject-reported pain intensity using a visual analog scale.

RESULTS

Pilot study: Subjects who received the heated patch (n=43) vs. the unheated patch (n=37) had lower mean pain intensity scores (14.7 vs. 23.5mm, P=0.04). Pain intensity scores did not differ significantly by application time, but the difference between the 16 and 18 G catheter groups approached statistical significance (22.8 vs. 14.9 mm, P=0.05). Definitive study: Mean pain intensity scores for the heated patch group (n=124) vs. the unheated patch group (n=126) were 14.2 and 20.5mm, respectively (P=0.006).

CONCLUSION

Heated patches provided significantly better pain relief compared with unheated patches. All the subjects tolerated the patches well, with few adverse effects.

Pharmacologic approaches for reducing venous access pain in children

A variety of pharmacologic options are available to clinicians who want to provide effective and safe topical local anesthesia to children undergoing venous access procedures. These options can be distinguished on the basis of how they deliver active drug through the impermeable outer layer of skin, the stratum corneum, to pain receptors located in the dermis and epidermis. Three general methodologies are typically used to bypass the stratum corneum: direct injection of local anesthetics, usually via a small-gauge hypodermic syringe; passive diffusion from topical creams or gels; and active needle-free drug strategies that enhance the rate of drug passage into the dermis and epidermis. Examples of the latter mechanisms include heat-enhanced diffusion, iontophoresis, sonophoresis, laser-assisted transdermal passage, and pressurized gas delivery of powdered drug particles. Pharmacologic options in this setting can also be distinguished on the basis of the time to onset of full anesthetic effect. Several available agents induce significant local anesthesia within 1 to 3 minutes of administration, or faster, allowing easy integration into the skin preparation and subsequent venous access procedure. In combination with nonpharmacologic approaches, these agents can be used to dramatically lessen this significant source of pediatric pain.

The effect of vapocoolant spray on pain due to intravenous cannulation in children: a randomized controlled trial

BACKGROUND

Established noninvasive pharmacologic means of alleviating pain and anxiety in children undergoing intravenous cannulation are time-consuming, and thus impractical for routine use in the emergency department. Vapocoolant sprays provide transient skin anesthesia within seconds of application. We compared the effect of a new vapocoolant spray to placebo on pain due to intravenous cannulation in children.

METHODS

In this double-blind randomized controlled trial, which we conducted between June 1 and Sept. 12, 2006, 80 children aged 6-12 years received either vapocoolant spray or placebo before cannulation. Children rated their pain using a 100-mm colour visual analogue scale. Secondary outcomes included success rate on first attempt at cannulation and pain ratings by the children's parents, nurses and child life specialists.

RESULTS

We found a modest but significant reduction in pain with the use of vapocoolant spray (mean difference 19 mm, 95% confidence interval [CI] 6-32 mm; p < 0.01). Cannulation on first attempt was more often successful with the use of vapocoolant spray (85.0%) than with placebo (62.5%) (mean difference 22.5%, 95% CI 3.2%-39.9%; p = 0.03). The number needed to treat to prevent 1 cannulation failure was 5 (95% CI 3-32). Parents (p = 0.04), nurses (p = 0.01) and child life specialists (p < 0.01) considered the children's pain to be reduced with the use of vapocoolant spray.

INTERPRETATION

The vapocoolant spray in our study quickly and effectively reduced pain due to intravenous cannulation in children and improved the success rate of cannulation. It is an important option to reduce childhood procedural pain in emergency situations, especially when time precludes traditional interventions. (http://ClinicalTrials.gov trial register no. NCT00130650.).

Use of the Synera™ Patch for Local Anesthesia Before Vascular Access Procedures: A Randomized, Double-Blind, Placebo-Controlled Study

OBJECTIVE

This randomized, double-blind, placebo-controlled, paired study compared the Synera patch, a drug delivery device comprised of an eutectic mixture of lidocaine (70 mg) and tetracaine (70 mg) whose onset is accelerated by a controlled heating device, with placebo. The objective of the study was to evaluate the efficacy of Synera in inducing local anesthesia before a vascular access procedure.

DESIGN

Before the vascular access procedures, adult volunteers randomly received a concurrent application of Synera and placebo to the right and left antecubital surfaces. Forty subjects received 20-minute treatments. After each vascular access procedure, efficacy evaluations were completed by the subject, investigator, and an independent observer. Median subject-reported pain intensity, using the visual analog scale scores (VAS, 0-100 mm scale) were significantly lower for Synera than placebo (5 mm vs 28 mm, P < 0.001).

RESULTS

Compared with placebo, more subjects reported adequate anesthesia following Synera (73% vs 31%, P = 0.002), and more subjects indicated they would use Synera again (70% vs 33%, P = 0.006). Investigators rated more subjects having no pain with Synera compared with placebo (63% vs 33%, P = 0.021), and more subjects having adequate anesthesia with Synera (60% vs 23%, P = 0.004). Independent observers rated 68% of subjects having no pain with Synera compared with 38% with placebo (P = 0.015). Side-effects were limited to localized pruritus and erythema. Erythema was more common with Synera than placebo (62% vs 42%, P = 0.018).

CONCLUSIONS

A 20-minute application of Synera consistently provided clinically useful anesthesia for vascular access procedures, and appears to be well suited for topical dermal anesthesia due to its reduced time required to produce adequate anesthesia and high subject and investigator acceptance.

Rhythmic pattern in pain and their chronotherapy

Pain control is one of the most important therapeutic priorities; nonetheless, inadequate pain relief remains a significant health care issue. Thus, it is important to determine whether the analgesic effect can be improved by using the chronopharmacological approach. This paper reviews the data on the rhythmic patterns in pain level and their chronotherapy. It underlines the major issues and problems related to the development of chronotherapeutic strategies, and it examines emerging aspects of new drug-delivery systems for achieving such.

Skin surgery in children: local anaesthesia and sedation techniques

In the past, procedural pain control in young children was undertreated as it was incorrectly alleged that their neuronal pain pathways were undeveloped. However, it is now recognised that even neonates are able to experience pain. Moreover, intensely painful physical experiences in childhood can have persisting physiological and psychological consequences. Therefore, the management of acute pain is essential. In this paper, the authors provide an in-depth discussion regarding the anaesthetic options for paediatric patients undergoing dermatological surgery.