Efficacy of erbium:yttrium-aluminum-garnet laser-assisted delivery of topical anesthetic

Hypertrophic Scars and Keloids: Advances in Treatment and Review of Established Therapies

Hypertrophic scars and keloids can have significant detrimental effects on patients both psychosocially and functionally. A careful identification of patient risk factors and a comprehensive management plan are necessary to optimize outcomes. Patients with a history of dystrophic scarring should avoid unnecessary procedures and enhance the wound-healing process using various preventive strategies. As there is no single, fully efficacious treatment modality, prevention remains the best approach in reducing aberrant scar formation. When prevention therapies fail, keloids have been shown to be respond to a variety of therapies including topical and injectable corticosteroids, 5-fluorouracil, radiotherapy, lasers, and surgical excision, all with varying efficacies. As such, management should be tailored to the individual patient's risk factors with the use of combination therapies to reduce recurrence rates. Still, keloid and hypertrophic scar therapies are widely diverse with novel treatment modalities providing alternatives for recurring lesions. Laser-assisted drug delivery, skin priming, and novel topical therapies may provide alternative options for the management of hypertrophic scars and keloids.

Laser-Assisted Drug Delivery in the Treatment of Scars, Rhytids, and Melasma: A Comprehensive Review of the Literature

Although broad reviews on laser-assisted drug delivery (LADD) have been published in the past, an updated focused examination of its utility in the context of common, treatment-resistant, dermatologic conditions has not been published. This article reports a comprehensive scoping review of the potential benefits of LADD compared to laser or drug monotherapy for the treatment of 3 such conditions: scars, rhytids, and melasma. A PubMed (National Institutes of Health; Bethesda, MD) search was conducted for keywords including "laser-assisted drug delivery," "scar," "rhytid," and "melasma." Out-of-scope studies were excluded. To evaluate the efficacy of LADD for the treatment of scars, relevant articles were categorized by scar type: hypertrophic/keloid, atrophic, and hypopigmented. LADD, with both ablative and nonablative laser types, was studied in combination with corticosteroids, botulinum toxin-A (BTX-A), 5-fluorouracil, 5-aminolevulinic acid photodynamic therapy, stem cells, platelet-rich plasma, and prostaglandin analogs for the treatment of scars. Some randomized controlled trials demonstrated the efficacy of LADD, whereas others showed no significant differences in clinical outcomes but demonstrated reduced adverse effects. Regarding rhytids, laser treatment has been combined with various cosmeceuticals, including poly-L-lactic acid, topical retinaldehyde, and topical BTX-A. The studies reviewed supported the use of LADD with these drugs over monotherapy. Some studies showed that LADD was effective for the absorption of drugs such as poly-L-lactic acid and BTX-A which are often not effective topically. For melasma treatment, LADD with tranexamic acid and hydroquinone was superior in some studies, but not significantly different than monotherapy in other studies. LADD with certain drugs could be considered to treat scars, rhytids, and melasma.

LEVEL OF EVIDENCE: 5

Evidence-Based Clinical Practice Guidelines for Laser-Assisted Drug Delivery

Importance

Laser-assisted drug delivery (LADD) is used for various medical and cosmetic applications. However, there is insufficient evidence-based guidance to assist clinicians performing LADD.

Objective

To develop recommendations for the safe and effective use of LADD.

Evidence Review

A systematic literature review of Cochrane Central Register of Controlled Trials, Embase, and MEDLINE was conducted in December 2019 to identify publications reporting research on LADD. A multidisciplinary panel was convened to draft recommendations informed by the systematic review; they were refined through 2 rounds of Delphi survey, 2 consensus meetings, and iterative review by all panelists until unanimous consensus was achieved.

Findings

Of the 48 published studies of ablative fractional LADD that met inclusion criteria, 4 were cosmetic studies; 21, oncologic; and 23, medical (not cosmetic/oncologic), and 6 publications of nonablative fractional LADD were included at the request of the expert panel, producing a total of 54 studies. Thirty-four studies (63.0%) were deemed to have low risk of bias, 17 studies (31.5%) had moderate risk, and 3 (5.5%) had serious risk. The key findings that informed the guidelines developed by the expert panel were as follows: LADD is safe in adults and adolescents (≥12 years) with all Fitzpatrick skin types and in patients with immunosuppression; it is an effective treatment for actinic keratosis, cutaneous squamous cell carcinoma in situ, actinic cheilitis, hypertrophic scars, and keloids; it is useful for epidermal and dermal analgesia; drug delivery may be increased through the application of heat, pressure, or occlusion, or by using an aqueous drug solution; laser settings should be selected to ensure that channel diameter is greater than the delivered molecule; antibiotic prophylaxis is not recommended, except with impaired wound healing; antiviral prophylaxis is recommended when treating the face and genitalia; and antifungal prophylaxis is not recommended. The guideline's 15 recommendations address 5 areas of LADD use: (I) indications and contraindications; (II) parameters to report; (III) optimization of drug delivery; (IV) safety considerations; and (V) prophylaxis for bacterial, viral, and fungal infections.

Conclusions and Relevance

This systematic review and Delphi consensus approach culminated in an evidence-based clinical practice guideline for safe and effective use of LADD in a variety of applications. Future research will further improve our understanding of this novel treatment technique.

Evaluating the Efficacy of the Er,Cr:YSGG Fractional Laser Before Treatment With Triamcinolone NN Ointment in Oral Lichen Planus Lesions

Introduction: It has been demonstrated that laser technology can enhance topical drug absorption. This study aimed to determine the effects of Er,Cr:YSGG laser radiation before the application of topical corticosteroids in the healing of oral lichen planus. Methods: In this double-blind split-mouth clinical trial, 32 lesions were chosen from eight patients affected by oral lichen planus (OLP). The oral lesions were randomly categorized into two groups. The first group had topical treatment with triamcinolone NN ointment and the second group had laser radiation (Er,Cr:YSGG) for eight weeks before starting the ointment. For each lesion, the irritating level based on the VAS score, the lesion level based on the Thongprasom scale score, and the healing time were measured, and the collected data were analyzed by the Friedman test and the Wilcoxon's statistical test. Results: The mean healing time based on the verbal analog scale (VAS) score was not significantly different between the two treatment groups (P>0.05). The mean healing time based on Thongprasom scale scores did not show any significant difference between the two treatment groups (P>0.05). Conclusion: The application of the Er,Cr:YSGG laser before treatment with triamcinolone NN ointment did not show any advantage for the average healing time compared to a medicine regimen with only triamcinolone NN ointment.

Lessons Learned from the First Decade of Laser-Assisted Drug Delivery

Laser-assisted drug delivery augments the distribution and penetration of topically applied treatments, leading to enhanced delivery and bioavailability. We discuss the therapeutic application of laser-assisted drug delivery in clinical practice in cases of non-melanoma skin cancer, vitiligo, melasma, scarring, and alopecia (female pattern hair loss, male pattern hair loss, alopecia areata) as well as for vaccination, local anaesthesia, analgesia, viral warts, infantile haemangiomas and cosmetic uses, and we review clinical studies that have used this technique over the last decade. Our review shows that the application of laser-assisted drug delivery enhances topical agent efficacy, potentially reducing the agent concentration and duration of topical treatment required. Future research into the use of laser-assisted drug delivery before topical therapies is needed to establish the optimal techniques to enhance drug delivery and thus improve patient outcomes.

Efficacy of Er,Cr:YSGG laser-assisted delivery of topical anesthesia in the oral mucosa

OBJECTIVE

Lasers which can reduce epithelium thickness will enhance the penetration of topical drugs. To date, no study has assessed the efficacy of this technique in the oral mucosa. The aim of this study was the evaluation of efficacy of this technique in increasing the effect of topical anesthesia in the oral mucosa.

MATERIALS AND METHODS

On 20 volunteers, half of the lower lip mucosa was irradiated with Er,Cr:YSGG laser with 2780 nm wavelength and 1.3 J/cm² energy for 1 min; then, topical lidocaine was applied on the entire lower lip mucosa. After 5 min, a 27-gauge needle was inserted to each half of the lip mucosa, and the length of the needle inserted into the mucosa without feeling pain was considered the depth of insertion. This measurement was repeated every 15 min for 1 h.

RESULTS

The mean depth of anesthesia at the control side was 6.95 ± 2.43, 8.45 ± 4.05, 6.5 ± 3.00, and 3.85 ± 2.08 mm at 5, 20, 35, and 60 min, respectively. These values at the test side were 12.25 ± 5.42, 13.25 ± 5.02, 11.4 ± 5.03, and 9.10 ± 5.84 mm, respectively. According to repeated-measures ANOVA, the effect of the type of the treatment on the depth of insertion was significant (P < 0.001).

CONCLUSIONS

The results showed that irradiation of Er,Cr:YSGG laser before the topical application of the anesthetic agents on the oral mucosa increases their efficacy.

CLINICAL RELEVANCE

Topical anesthesia is used to enhance dental procedures painlessly, but there is controversy in their efficacy. Laser-assisted drug delivery to the oral mucosa can enhance their efficacy.

Safety of local anesthetics

Local anesthetics are essential medications for the conduction of dermatological procedures. They stop the depolarization of nerve fibers and are divided into two main categories, the amide and ester types. Systemic toxicity with reflex on the central nervous and cardiovascular systems is their most feared adverse reactions, and the anaphylactic reaction is the most concerning one. Although potentially fatal, these events are extremely rare, so local anesthetics are considered safe for use in in-office procedures.

Randomized, double-blind, phase III clinical study of a novel nanotechnological topical anesthetic formulation containing lidocaine 25 mg/g and prilocaine 25 mg/g (nanorap) in skin phototypes I-III patients with ablative fractional CO2 laser treatment indication in the forehead

BACKGROUND AND OBJECTIVES

Nanotechnology may increase the speed of penetration into the skin. This study evaluated the efficacy, safety, and pharmacokinetics of a novel topical anesthetic nanocapsule formulation (2 g) containing 2.5% lidocaine and 2.5% prilocaine (nanorap-test formulation) compared to placebo (control formulation) in skin types I-III patients of both sexes submitted to the ablative fractional CO₂ laser treatment.

METHODS

The patients (n = 120) included in this double-blind, single-center, randomized trial, received topical application of 2 g of the test formulation (50 mg lidocaine + 50 mg prilocaine) and placebo on the forehead region. Efficacy was assessed as pain sensation in four quadrants of each side of the forehead using a visual analogue scale immediately (0 min) and at 30, 60, and 90 minutes after laser application compared to placebo. The safety and tolerability of the test product were evaluated based on the occurrence of systemic adverse events as well as the occurrence of immediate and late skin reactions. Pharmacokinetic evaluation was performed in plasma of eight patients using a validated LC-MS/MS method for drugs quantification.

RESULTS

Nanorap induced a clinically significant reduction in the pain assessment at all evaluated times (57.2%, 41.6%, 38.6%, and 37.3% at 0, 30, 60, and 90 minutes after drug application, respectively. Mean values of C_max were 14.20 and 5.36 ng/ml and t_max were 3.5 and 1.8 hour for lidocaine and prilocaine, respectively. No systemic adverse events were observed.

CONCLUSION

The nanorap formulation demonstrated a clinically and statistically significant efficacy providing analgesia after the ablative fractional CO₂ laser therapy in the investigated patients, when compared to placebo. The product also presented good safety and tolerability. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Laser-assisted drug delivery: mode of action and use in daily clinical practice

Topical application of pharmaceutical agents is a basic principle of dermatological therapy. However, the effective barrier function of the skin significantly impairs the bioavailability of most topical drugs. Fractional ablative lasers represent an innovative strategy to overcome the epidermal barrier in a standardized, contact-free manner. The bioavailability of topical agents can be significantly enhanced using laser-assisted drug delivery (LADD). In recent years, the principle of LADD has become well established for various dermatological indications. Herein, we review the current literature on LADD and present potential future applications.

Update of Ablative Fractionated Lasers to Enhance Cutaneous Topical Drug Delivery

Ablative fractional lasers (AFXL) enhance uptake of therapeutics and this newly emerging field is called laser-assisted drug delivery (LAD). This new science has emerged over the past decade and is finding its way into clinical practice. LAD is poised to change how medicine delivers drugs. Topical and systemic application of pharmaceutical agents for therapeutic effect is an integral part of medicine. With topical therapy, the stratum corneum barrier of the skin impairs the ability of drugs to enter the body. The purpose of LAD is to alter the stratum corneum, epidermis, and dermis to facilitate increased penetration of a drug, device, or cell to its respected target. AFXL represents an innovative, non-invasive strategy to overcome the epidermal barrier. LAD employs three steps: (1) breakdown of the skin barrier with a laser, (2) optional use a laser for a therapeutic effect, (3) delivery of the medicine through laser channels to further enhance the therapeutic effect. The advantages of using lasers for drug delivery include the ease of accessibility, the non-invasive aspect, and its effectiveness. By changing the laser settings, one may use LAD to have a drug remain locally within the skin or to have systemic delivery. Many drugs are not intended for use in the dermis and so it has yet to be determined which drugs are appropriate for this technique. It appears this developing technology has the ability to be a new delivery system for both localized and systemic delivery of drugs, cells, and other molecules. With responsible development AFXL-assisted drug delivery may become a new important part of medicine.

Laser-Assisted Delivery to Treat Facial Scars

Treatment of facial scars is a multispecialty endeavor for optimal patient recovery. One new innovation helping in facial scar treatments are lasers. Fractional laser predictably (tunable) disrupts the barrier of the skin creating deep channels that allow the delivery of drug and cellular materials; this is called laser-assisted drug delivery (LAD). Without exception thus far, LAD has been found to enhance the local uptake of any drug or substance applied to the skin. These zones may be used postoperatively to deliver drugs and other substances to create an enhanced scar therapeutic response to drug or substance applied to the skin.

Non-invasive anaesthetic methods for dermatological laser procedures: a systematic review

Pain is a common side-effect of dermatological laser procedures. Non-invasive anaesthetic drugs and anaesthetic procedures can be used to provide pain relief and increase patient satisfaction and treatment efficacy. However, it remains unclear which method provides the best pain relief. The objective of this systematic review was therefore to assess the efficacy and safety of non-invasive anaesthetic methods during dermatological laser procedures. A systematic literature search was conducted. Randomized and non-randomized controlled clinical trials (RCTs and CCTs) were included. Two authors independently assessed study eligibility, extracted data and assessed the risk of bias. The quality of evidence was rated using Grading of Recommendations Assessment, Development and Evaluation (GRADE). Twenty RCTs and 12 CCTs were included, involving nine different laser indications: hair removal (n = 9), resurfacing/rejuvenation (n = 5), port wine stains (n = 8), leg telangiectasia (n = 3), facial telangiectasia (n = 2), tattoo removal (n = 2), naevus of Ota (n = 1), solar lentigines (n = 1) and HPV lesions (n = 1). The non-invasive anaesthetic methods (i.e. topical anaesthetic drugs, skin cooling, and pneumatic skin flattening [PSF]), types of lasers, laser settings, application time, and types of pain scales varied widely among the included studies. All of the studies had an unclear or high risk of bias, and the overall quality of evidence was rated as low. In general, active non-invasive anaesthetic methods seemed to provide favourable results compared to placebo or no anaesthesia, and topical anaesthetic drugs and PSF seemed to result in a better pain reduction than skin cooling. However, the current evidence is insufficient to provide recommendations for daily clinical practice. There is a need for more high-quality (head-to-head) RCTs. Future studies should also evaluate sex differences in pain perception, have uniformity with regard to validated pain measurement scales and address clinically significant differences in pain reduction besides statistically significant differences.

Laser assisted drug delivery: a review of an evolving technology

BACKGROUND

Topically applied drugs have a relatively low cutaneous bioavailability.

OBJECTIVE

This article reviews the existing applications of laser assisted drug delivery, a means by which the permeation of topically applied agents can be enhanced into the skin.

RESULTS

The existing literature suggests that lasers are a safe and effective means of enhancing the delivery of topically applied agents through the skin. The types of lasers most commonly studied in regards to drug delivery are the carbon dioxide (CO2 ) and erbium:yttrium-aluminum-garnet (Er:YAG) lasers. Both conventional ablative and fractional ablative modalities have been utilized and are summarized herein.

LIMITATIONS

The majority of the existing studies on laser assisted drug delivery have been performed on animal models and additional human studies are needed.

CONCLUSIONS

Laser assisted drug delivery is an evolving technology with potentially broad clinical applications. Multiple studies demonstrate that laser pretreatment of the skin can increase the permeability and depth of penetration of topically applied drug molecules for both local cutaneous and systemic applications.

Lasers as an approach for promoting drug delivery via skin

INTRODUCTION

Using lasers can be an effective drug permeation-enhancement approach for facilitating drug delivery into or across the skin. The controlled disruption and ablation of the stratum corneum (SC), the predominant barrier for drug delivery, is achieved by the use of lasers. The possible mechanisms of laser-assisted drug permeation are the direct ablation of the skin barrier, optical breakdown by a photomechanical wave and a photothermal effect. It has been demonstrated that ablative approaches for enhancing drug transport provide some advantages, including increased bioavailability, fast treatment time, quick recovery of SC integrity and the fact that skin surface contact is not needed. In recent years, the concept of using laser techniques to treat the skin has attracted increasing attention.

AREAS COVERED

This review describes recent developments in using nonablative and ablative lasers for drug absorption enhancement. This review systematically introduces the concepts and enhancement mechanisms of lasers, highlighting the potential of this technique for greatly increasing drug absorption via the skin. Lasers with different wavelengths and types are employed to increase drug permeation. These include the ruby laser, the erbium:yttrium-gallium-garnet laser, the neodymium-doped yttrium-aluminum-garnet laser and the CO2 laser. Fractional modality is a novel concept for promoting topical/transdermal drug delivery. The laser is useful in enhancing the permeation of a wide variety of permeants, such as small-molecule drugs, macromolecules and nanoparticles.

EXPERT OPINION

This potential use of the laser affords a new treatment for topical/transdermal application with significant efficacy. Further studies using a large group of humans or patients are needed to confirm and clarify the findings in animal studies. Although the laser fluence or output energy used for enhancing drug absorption is much lower than for treatment of skin disorders and rejuvenation, the safety of using lasers is still an issue. Caution should be used in optimizing the feasible conditions of the lasers in balancing the effectiveness of permeation enhancement and skin damage.

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

Topical local anesthetics in one form or another have been used for the past 20 years to alleviate the skin pain associated with needle puncture and venous cannulation in children. Although the application of topical anesthetic creams is painless compared with traditional local anesthetic infiltration of the skin and subcutaneous tissues prior to venipuncture and minor skin procedures, they remain underutilized, primarily due to their slow analgesic onset and inconsistent effectiveness. For a topical local anesthetic to be of practical use in busy clinical settings, it must be easy to apply, have minimal side effects, not require cumbersome equipment and be reasonably cost effective. Until recently, limitations in one or all of these areas have dissuaded pediatric practitioners from their routine use. However, recent advances in transdermal delivery technologies, have led to the emergence of a number of new delivery approaches that accelerate the onset time to 20 min or less and provide more consistent and deeper sensory skin analgesia. Although still in the early stages of investigation, technologies that promote the flux of drugs of all sizes through the skin by creating transient microchannels show great promise in circumventing the skin barrier and promoting the transdermal delivery of not only local anesthetics but also other drugs. Ultimately, the rationale to change clinical practice and use a new transdermal delivery system will depend upon the cost, ease of use, frequency of adverse events and the benefits to the patient relative to an alternative method.

Topical lidocaine enhanced by laser pretreatment: a safe and effective method of analgesia for facial rejuvenation

BACKGROUND

Injectable forms of anesthesia for nonsurgical facial rejuvenation, although efficacious, are uncomfortable for the patient. Preclinical studies have demonstrated that laser pretreatment at low energies enhances absorption of topical lidocaine.

OBJECTIVES

The authors assess the safety and efficacy of laser-assisted transdermal delivery of topical anesthetic.

METHOD

Ten patients were split into 2 groups (A and B). All patients received 15 g of BLT (20% benzocaine, 6% lidocaine, and 4% tetracaine triple anesthetic cream) for 20 minutes with no occlusion. Then the cream was removed and the first blood draw taken. Group A patients were pretreated with the full ablative laser and group B patients with a fractional ablative laser to the full face. A further 15 g BLT was applied for another 20 minutes. Group A patients then underwent full ablative laser treatment, and group B received fractionated ablative laser treatment. Blood draws were taken at 60, 90, 120, 180, and 240 minutes after the initial topical anesthetic application, and the serum was analyzed for lidocaine and monoethylglycinexylidide (MEGX) levels. Patients were asked to rate the pain felt at intervals during the procedure.

RESULTS

No patient required supplemental nerve blocks. Pain scores were equivalent at the end of the first pass for both groups (P = .436). Group A patients had significantly lower pain scores at the start of the second laser treatment (P = .045), but pain scores became equivalent by the end (P = .323). Combined serum lidocaine and MEGX levels were significantly higher in group A patients up to 90 minutes (peak average of 0.61 µg/mL for group A and 0.533 µg/mL for group B; P = .0253), which corresponded to greater initial analgesic effect.

CONCLUSIONS

Data from this study demonstrate that topical anesthetic for facial rejuvenation can be enhanced with laser pretreatment while maintaining safe blood serum levels. Further studies should examine optimal application amount and time to allow safe multipass facial rejuvenation without the need for invasive nerve blocks.

Anesthesia methods in laser resurfacing

Laser resurfacing technology offers the ability to treat skin changes that are the result of the aging process. One of the major drawbacks of laser resurfacing technologies is the pain associated with the procedure. The methods of anesthesia used in laser resurfacing to help minimize the pain include both noninvasive and invasive procedures. The noninvasive procedures can be divided into topical, cryoanesthesia, and a combination of both. The invasive methods of anesthesia include injected forms (infiltrative, nerve blocks, and tumescent anesthesia) and supervised anesthesia (monitored anesthesia care and general anesthesia). In this review, the authors summarize the types of anesthesia used in laser resurfacing to aid the provider in offering the most appropriate method for the patient to have as painless a procedure as possible.

Next generation intra- and transdermal therapeutic systems: using non- and minimally-invasive technologies to increase drug delivery into and across the skin

The number of drug molecules approved by the regulatory authorities for transdermal administration is relatively modest - less than two dozen. Many other therapies might benefit from the advantages offered by the transdermal route. That they have not already done so is due to the exceptional efficacy of the stratum corneum as a diffusional barrier and its remarkable ability to restrict molecular transport. As a result only extremely potent therapeutics possessing the necessary physicochemical properties can be delivered by passive diffusion across intact skin at pharmacologically relevent rates. This has led to the development of several delivery technologies that might be used to expand the range of medicinal agents that can be administered transdermally with the requisite delivery kinetics. There are essentially two approaches: (i) provide an improved driving force to increase the rate of transport (i.e., act on the molecule) or (ii) modify the properties of the microenvironment through which diffusion must occur (i.e., act on the stratum corneum). The challenge for the latter approach is to compromise the barrier in a reversible and relatively painless manner that minimises irritation, is practical for chronic conditions and has minimal risk of infection. Here, we review some of the physical methods that have been used to either transiently perturb the skin barrier or to provide additional driving forces to facilitate molecular transport with a particular focus on technologies that have either led to marketed products or have at least reached the clinical development stage.

Ablative fractional resurfacing in topical drug delivery: an update and outlook

BACKGROUND

The effective delivery of therapeutic molecules to varied targets in the skin and elsewhere has been an area of ongoing research and development.

OBJECTIVE

To review the structure of the skin with an emphasis on topical drug delivery and to present the rationale for the use of ablative and nonablative fractional resurfacing in assisted drug delivery.

METHODS AND MATERIALS

Review of the currently available scientific literature on laser-assisted drug delivery.

RESULTS

A number of strategies can be employed to enhance topical drug delivery. Ablative fractional resurfacing (AFR) has been demonstrated to be effective in enhancing drug delivery. Further studies are needed to assess the use of nonablative fractional resurfacing in assisted drug delivery.

CONCLUSION

AFR-assisted drug delivery is a promising tool for the future of dermatology. We expect to see a number of agents to be paired with AFR for enhanced drug delivery. Further investigation is necessary to evaluate appropriate drug specific channel density and depth parameters. Factors that must be considered include the physicochemical properties of the drug, the target tissue, skin wounding, and cost when evaluating the drugs and conditions that will most benefit from this promising new drug delivery system.

Can fractional lasers enhance transdermal absorption of topical lidocaine in an in vivo animal model?

BACKGROUND AND OBJECTIVE

It has been shown in vitro that pretreatment of skin with fractional lasers enhances transdermal delivery of drugs. The aim of this study is to demonstrate in vivo firstly that laser enhances transdermal drug absorption and secondly that this can be manipulated by altering laser settings.

STUDY DESIGN/MATERIALS AND METHODS

Four pigs were used in the IACUC approved animal study. On day 0, 5 g of 4% topical lidocaine was applied under occlusion for 60 minutes to a 400 cm(2) area on the abdomen. Blood was drawn at 0, 60, 90, 120, 180, and 240 minutes. On day 7, the Er:YAG laser was used at 500, 250, 50, and 25 µm ablative depth, respectively, over a 400 cm(2) area on the abdomen. Five grams of 4% topical lidocaine was applied immediately with occlusion for 60 minutes, and then removed. Blood was drawn at 0, 60, 90, 120, 180, and 240 minutes. The serum was extracted and analyzed for lidocaine and its metabolite monoethylglycinexylidide (MEGX).

RESULTS

Serum levels of lidocaine and MEGX were undetectable in untreated skin. Following laser treatment both lidocaine and MEGX were detectable. Peak levels of lidocaine were significantly higher (P = 0.0002) at 250 µm (0.62 mg/L), compared to 500 µm (0.45 mg/L), 50 µm (0.48 mg/L), and 25 µm (0.3 mg/L). Peak levels of MEGX were significantly higher (P ≤ 0.0001) at 250 µm (0.048 mg/L), compared to 500 µm (0.018 mg/L), 50 µm (0.036 mg/L), and 25 µm (0.0144 mg/L).

CONCLUSIONS

This study demonstrates that laser pretreatment significantly increases absorption of topical lidocaine so that it is detectable in the blood and that manipulating laser settings can affect drug absorption. Future work will look at translating this effect into clinical benefit.

Erbium:YAG fractional laser ablation for the percutaneous delivery of intact functional therapeutic antibodies

The physicochemical properties and stability requirements of therapeutic proteins necessitate their parenteral administration even for local therapy; however, unnecessary systemic exposure increases the risk of avoidable side-effects. The objective of this study was to use fractional laser ablation to enable the delivery of intact, functional therapeutic antibodies into the skin in vitro and in vivo. The laser-assisted delivery of Antithymocyte globulin (ATG) and Basiliximab - FDA-approved therapeutics for the induction of immunosuppression - was investigated. In vitro delivery experiments were performed using dermatomed porcine ear and human abdominal skins; an in vitro/in vivo correlation was shown using C57 BL/10 SCSnJ mice. Antibody transport was quantified by using ELISA methods developed in-house. Results showed that increasing the pore number from 300 to 450 and 900, increased total antibody delivery (sum of amounts permeated and deposited); e.g., for ATG, from 1.18±0.10 to 3.98±0.64 and 4.97±0.83 μg/cm(2), respectively - corresponding to 19.7-, 66.3- and 82.8-fold increases over the control (untreated skin). Increasing laser fluence from 22.65 to 45.3 and 135.9J/cm(2) increased total ATG delivery from 1.70±0.65 to 4.97±0.83 and 8.70±1.55 μg/cm(2), respectively. The Basiliximab results confirmed the findings with ATG. Western blot demonstrated antibody identity and integrity post-delivery; human lymphocyte cytotoxicity assays showed that ATG retained biological activity post-delivery. Immunohistochemical staining was used to visualize ATG distribution in the epidermis. Total ATG delivery across porcine ear and human abdominal skin was statistically equivalent and an excellent in vitro/in vivo correlation was observed in the murine model. Based on published data, the ATG concentrations achieved in the laser-porated human skins were in the therapeutic range for providing local immunosuppression. These results challenge the perceived limitations of transdermal delivery with respect to biopharmaceuticals and suggest that controlled laser microporation provides a less invasive, more patient-friendly "needle-less" alternative to parenteral administration for the local delivery of therapeutic antibodies.

Fractional CO(2) laser-assisted drug delivery

BACKGROUND AND OBJECTIVES

Ablative fractional resurfacing (AFR) creates vertical channels that might assist the delivery of topically applied drugs into skin. The purpose of this study was to evaluate drug delivery by CO(2) laser AFR using methyl 5-aminolevulinate (MAL), a porphyrin precursor, as a test drug.

MATERIALS AND METHODS

Two Yorkshire swine were treated with single-hole CO(2) laser AFR and subsequent topical application of MAL (Metvix(R), Photocure ASA, Oslo, Norway), placebo cream and no drug. MAL-induced porphyrin fluorescence was measured by fluorescence microscopy at skin depths down to 1,800 microm. AFR was performed with a 10.6 microm wavelength prototype CO(2) laser, using stacked single pulses of 3 millisecond and 91.6 mJ per pulse.

RESULTS

AFR created cone-shaped channels of approximately 300 microm diameter and 1,850 microm depth that were surrounded by a 70 microm thin layer of thermally coagulated dermis. There was no porphyrin fluorescence in placebo cream or untreated skin sites. AFR followed by MAL application enhanced drug delivery with significantly higher porphyrin fluorescence of hair follicles (P<0.0011) and dermis (P<0.0433) versus MAL alone at skin depths of 120, 500, 1,000, 1,500, and 1,800 microm. AFR before MAL application also enhanced skin surface (epidermal) porphyrin fluorescence. Radial diffusion of MAL from the laser-created channels into surrounding dermis was evidenced by uniform porphyrin fluorescence up to 1,500 microm from the holes (1,000, 1,800 microm depths). Skin massage after MAL application did not affect MAL-induced porphyrin fluorescence after AFR.

CONCLUSIONS

Ablative fractional laser treatment facilitates delivery of topical MAL deeply into the skin. For the conditions of this study, laser channels approximately 3 mm apart followed by MAL application could produce porphyrins throughout essentially the entire skin. AFR appears to be a clinically practical means for enhancing uptake of MAL, a photodynamic therapy drug, and presumably many other topical skin medications.

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.

Laser-assisted anesthesia reduces the pain of venous cannulation in children and adults: a randomized controlled trial

OBJECTIVES

Application of topical anesthetics before intravenous (IV) cannulation is effective yet limited by delayed transdermal absorption. The authors evaluated a handheld laser device to enhance topical anesthetic absorption by ablating the stratum corneum, the major barrier to drug absorption through the skin. The hypothesis was that laser-assisted anesthesia would reduce the pain of IV cannulation in emergency department (ED) patients.

METHODS

This was a blinded, randomized, controlled trial. ED patients aged 1 year and older requiring nonemergent IV cannulation were included. Patients were randomized to pretreatment of the skin with laser or sham laser, and standardized venous cannulation was performed on the dorsum of the patients' hands or antecubital fossa. In the experimental group, the area over the target vein was pretreated with a lightweight, portable Er:YAG unit, with a fluence of 3.5 J/cm2, a pulse width of 600 microseconds, and a spot diameter of 6 mm. Lidocaine 4% cream was applied to the area immediately after laser application. Five minutes later, the cream was wiped off and a trained nurse inserted an IV catheter. In the control group, a sham laser and lidocaine were used. Pain of laser application and IV cannulation was recorded on age-appropriate pain scales; presence of infection or abnormal pigmentation was determined at one week. Pain of cannulation was compared using parametric and nonparametric tests.

RESULTS

Sixty-one patients were randomized to laser (30) and sham (31) pretreatment. Mean (+/- SD) age was 27 (+/- 21) years, 49% were female, and one half were children younger than 18 years. The mean pain of IV cannulation was significantly less (mean difference, 28.3 mm; 95% confidence interval = 17.9 to 38.7) in patients pretreated with the laser (10.0 mm; 95% confidence interval = 4.4 to 15.6) than with sham laser (38.3 mm; 95% confidence interval = 29.3 to 42.2). The difference in children was also significant. Application of the laser was painless in most patients. No patient developed infection or abnormal pigmentation.

CONCLUSIONS

Pretreatment of the skin with a laser device followed by a five-minute topical lidocaine 4% application reduces the pain of IV cannulation in ED adult and pediatric patients.

Self-warming lidocaine/tetracaine patch effectively and safely induces local anesthesia during minor dermatologic procedures

BACKGROUND

Dermatologic procedures often cause some degree of pain. A self-warming patch containing lidocaine and tetracaine (L/T) was developed to provide topical local anesthesia prior to painful procedures.

OBJECTIVES

To evaluate the safety and efficacy of a self-warming L/T patch to provide anesthesia in adult patients undergoing minor dermatologic procedures.

METHODS

An active or placebo study drug was placed on adults 30 minutes prior to minor dermatologic surgical procedures in a prospectively randomized, double-blinded manner. Subcutaneous lidocaine injection was available during the procedure as a rescue medication if requested by the subject. Immediately following the procedure, the subjects, the investigator, and an independent observer rated pain intensity and adverse events were recorded.

RESULTS

Patient-reported pain intensity was significantly lower in the L/T patch group (p<.001). Investigators and an independent observer rated the pain in the L/T patch group to be less than in the placebo patch group (p = .004 and p<.001, respectively). Forty-nine percent of patients in the placebo group required rescue subcutaneous lidocaine compared with 22% in the L/T patch study group (p = .008). One patient in the L/T patch group reported a transient moderate burning sensation.

CONCLUSION

The self-warming L/T patch was effective in providing clinically useful local anesthesia for minor dermatologic procedures in adult patients.

Combined 5-Fluorouracil and Er:YAG Laser Treatment in a Case of Recurrent Giant Keratoacanthoma of the Lower Leg

BACKGROUND

Keratoacanthomas are fast-growing squamous tumors, which usually show spontaneous regression. The development of giant variants with an aggressive behavior has been described. Although surgical excision remains the treatment of choice for very large keratoacanthomas, other therapeutic options including laser surgery and topical chemotherapy may be superior in special situations.

OBJECTIVE

The objective was to evaluate the efficacy of Er:YAG laser surgery combined with topical 5-fluorouracil treatment in a case of recurrent giant keratoacanthoma.

METHODS

A 64-year-old woman presented for evaluation and treatment of recurrent tumors in her face and extremities. Despite repeated invasive surgical removal of these lesions, recurrence of fast-growing giant keratoacanthomas developed in the pretibial region of her left lower leg. Owing to recurrence after conventional surgery and the tumor size, a novel treatment method using ablative Er:YAG laser combined with topical 5-fluorouracil was performed.

RESULTS

After four treatments with excellent patient compliance, histologic analysis of punch biopsies revealed tumor-free ulcerations. Complete epithelization was obtained after 9 weeks. Six months after the treatment, no recurrence was observed.

CONCLUSION

The combined use of ablative Er:YAG laser and topical 5-fluorouracil chemotherapy may be considered as an effective treatment option in cases of giant keratoacanthoma when conventional surgery is not indicated.

Erbium:YAG Laser Pretreatment Accelerates the Response of Bowen's Disease Treated by Topical 5-Fluorouracil

BACKGROUND

Topical 5-fluorouracil (5-FU) is a standard treatment for Bowen's disease. However, its efficacy may be limited by the presence of stratum corneum. The Er:YAG laser has shown a dramatic enhancement effect on the delivery of 5-FU in vitro by ablation of the stratum corneum. The efficacy of laser-assisted delivery of 5-FU has not been tested in human.

OBJECTIVE

To see whether Er:YAG laser pretreatment can improve the efficacy of topical 5-FU in the treatment of Bowen's disease.

METHODS

Three target lesions from a patient with multiple Bowen's disease were selected for a half-side comparison study. The Er:YAG laser was used to remove the cornified layer on one side of each lesion, followed by twice-daily application of 5-FU cream to both sides. Clinical and histologic responses were compared.

RESULTS

Lesions pretreated with the Er:YAG laser showed more rapid clinical and histologic responses to topical 5-FU than those treated with 5-FU alone. Evaluation at 9 months after treatment showed no recurrences of lesions on both sides.

CONCLUSIONS

Our preliminary study demonstrates that this Er:YAG laser-assisted modality is effective and shows accelerated clinical response and shortened treatment time compared with topical 5-FU as a single treatment.