Lidocaine-Liposomes-A Promising Frontier for Transdermal Pain Management

(1) Background: We aim to develop novel gel formulations for transdermal drug delivery systems in acute and inflammatory pain therapy. (2) Methods: We induced inflammation by the injection of λ-carrageenan on the hind paw of 80 Wistar male rats. The animals were randomized into eight groups of 10 rats each: C (placebo gel), E (EMLATM), L (lidocaine 2%), L-CD (lidocaine + cyclodextrin 2.5%), L-LP (lidocaine + liposomes 1.7%), L-CS (lidocaine + chitosan 4%), L-CSh (lidocaine + chitosan hydrochloride), and L-CS-LP (lidocaine + chitosan + liposomes). The behavior response was determined with a hot plate, cold plate, and algesimeter, each being performed at 30, 60, 120, 180, and 240 min after pain induction. At the end of the experiment, tissue samples were collected for histological assessment. (3) Results: L-LP had the greatest anesthetic effects, which was proven on the cold plate test compared to placebo and EMLATM (all p ≤ 0.001). L-CS-LP had a significant effect on cold plate evaluation compared to placebo (p ≤ 0.001) and on hot plate evaluation compared to EMLATM (p = 0.018). (4) Conclusions: L-LP is a new substance with a substantial analgesic effect demonstrated by the cold plate in the first 120 min. Further studies with more animals are needed to determine the maximum doses that can be applied for a better analgesia with minimum side effects.

Does Topical Anesthesia Alter the Outcomes of Vascular Laser Procedures? Review of Vasodynamic Effects and Clinical Outcomes Data

BACKGROUND

Topical anesthesia has vasodynamic effects within the skin and therefore has the potential to change the presence of hemoglobin as a chromophore before intense pulsed light (IPL) and vascular laser treatments. It is unclear whether this is clinically relevant. Global consensus on the use of topical anesthetics in this context is lacking.

OBJECTIVE

Review the effects of topical anesthetics on the skin microvasculature and the clinical implications of such effects on vascular treatments.

METHODS

PubMed and Medline searches were performed to identify studies examining the vasodynamic effects of topical anesthesia on skin and evaluating differences in efficacy of IPL and vascular laser treatments with or without topical anesthetic use.

RESULTS

Published studies reveal variable effects of different topical anesthetic agents on skin microvasculature. Only 3 controlled studies that directly examined the effect of topical anesthesia on clinical outcomes for pulsed dye laser (PDL) treatment of vascular conditions were identified. They did not support a difference in clinical outcomes with or without the use of topical anesthesia before PDL treatment.

CONCLUSION

Although topical anesthetic agents have vasodynamic effects within the skin, there is currently insufficient evidence to advise against their use before light and laser-based vascular treatments.

The Efficacy of Pulsed Dye Laser Pretreated With or Without Local Anesthetic on Patients Presenting With Erythema of Face, Neck, Chest, and Extremities

BACKGROUND AND OBJECTIVES

Erythema is one of the most common cosmetic concerns and usually responds well to pulsed dye laser (PDL) treatment. As this laser can cause significant discomfort, topical anesthesia is sometimes offered. However, it is still uncertain whether topical anesthetics can affect the outcome of the laser therapy. We performed a retrospective single site study to compare the efficacy of PDL for the treatment of erythema in patients with and without pretreatment with topical anesthetic.

STUDY DESIGN/MATERIALS AND METHODS

A chart review was performed and patients who presented with erythema of face, neck, chest, and extremities pretreated with topical anesthesia (23% lidocaine/7% tetracaine ointment or 7% lidocaine/7% tetracaine ointment) undergoing PDL were reviewed and compared with another group without anesthesia. Two blinded dermatologists evaluated the postlaser procedure photographs and gave an assessment compared with baseline.

RESULTS

A total of 69 patient charts were reviewed. The erythema resulted from various skin conditions including telangiectasia, cherry angioma, striae, and rosacea. The mean improvement was 2.2581 in the anesthesia group and 2.2632 in the nonanesthesia group. There was no significant difference between both groups as confirmed by a noninferiority test.

CONCLUSIONS

Topical anesthesia with lidocaine and tetracaine ointment do not interfere with the efficacy of the PDL. Since pain management is essential for any cosmetic procedure, the application of a local anesthetic will enhance patient comfort and satisfaction during treatment with PDL. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

First-time success with needle procedures was higher with a warm lidocaine and tetracaine patch than an eutectic mixture of lidocaine and prilocaine cream

AIM

More than 50% of children report apian during venepuncture or intravenous cannulation and using local anaesthetics before needle procedures can lead to different success rates. This study examined how many needle procedures were successful at the first attempt when children received either a warm lidocaine and tetracaine patch or an eutectic mixture of lidocaine and prilocaine (EMLA) cream.

METHODS

We conducted this multicentre randomised controlled trial at three tertiary-level children's hospitals in Italy in 2015. Children aged three to 10 years were enrolled in an emergency department, paediatric day hospital and paediatric ward and randomly allocated to receive a warm lidocaine and tetracaine patch or EMLA cream. The primary outcome was the success rate at the first attempt.

RESULTS

The analysis included 172 children who received a warm lidocaine and tetracaine patch and 167 who received an EMLA cream. The needle procedure was successful at the first attempt in 158 children (92.4%) who received the warm patch and in 142 children (85.0%) who received the cream (p = 0.03). The pain scores were similar in both groups.

CONCLUSION

This study showed that the first-time needle procedure success was 7.4% higher in children receiving a warm lidocaine and tetracaine patch than EMLA cream.

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.

Microcirculatory effect of topical vapocoolants

BACKGROUND

Vapocoolant sprays are commonly used to minimize pain following minor interventions such as venipuncture, shave biopsy or needle insertion. Although these sprays have been widely used in clinical practice, little is known about their effect on microcirculation or cutaneous blood flow.

OBJECTIVE

To evaluate the real-time effect of a topical vapocoolant using a well-established, rat cremaster muscle microcirculatory model, allowing direct measurement of changes in vessel diameter, capillary density and leukocyte behaviour.

METHODS

Fifty rats were divided into a control and four experimental groups: group 1: 4 s spray with vapocoolant at 18 cm distance; group 2: 10 s spray at 18 cm distance; group 3: 4 s spray at 8 cm distance; and group 4: 10 s spray at 8 cm distance. Vessel diameters, capillary density and leukocyte behaviour were monitored for 1 h thereafter. Muscle was harvested for immunohistochemistry analysis of proangiogenic markers (vascular endothelial growth factor and von Willebrand factor), leukocyte behaviour markers (E-selectin, vascular cell adhesion molecule, intercellular adhesion molecule), pimonidazole-hypoxia staining and ApopTag (Millipore, USA) staining for apoptosis. Gene expression for inflammatory markers (interleukin [IL]-1β, IL-2, IL-4, IL-6, IL-10, tumour necrosis factor-alpha and interferon-gamma) was evaluated using polymerase chain reaction and myeloperoxidase assay for inflammation was performed.

RESULTS

The use of refrigerant spray decreased vessel diameter and capillary density initially, although none of these decreases were statistically significant. Polymerase chain reaction showed no significant changes. The myeloperoxidase assay showed statistically significant increase in myeloperoxidase activity in groups 2, 3 and 4. Immunohistochemistry was negative for angiogenic and proinflammatory markers.

CONCLUSIONS

The lack of statistically significant changes in vessel diameter and inflammatory markers corroborated the safety on microcirculation.

Microcirculatory effect of topical vapocoolants

Background

Vapocoolant sprays are commonly used to minimize pain following minor interventions such as venipuncture, shave biopsy or needle insertion. Although these sprays have been widely used in clinical practice, little is known about their effect on microcirculation or cutaneous blood flow.

Objective

To evaluate the real-time effect of a topical vapocoolant using a well-established, rat cremaster muscle microcirculatory model, allowing direct measurement of changes in vessel diameter, capillary density and leukocyte behaviour.

Method

Fifty rats were divided into a control and four experimental groups: group 1: 4 s spray with vapocoolant at 18 cm distance; group 2: 10 s spray at 18 cm distance; group 3: 4 s spray at 8 cm distance; and group 4: 10 s spray at 8 cm distance. Vessel diameters, capillary density and leukocyte behaviour were monitored for 1 h thereafter. Muscle was harvested for immunohistochemistry analysis of proangiogenic markers (vascular endothelial growth factor and von Willebrand factor), leukocyte behaviour markers (E-selectin, vascular cell adhesion molecule, intercellular adhesion molecule), pimonidazole-hypoxia staining and ApopTag (Millipore, USA) staining for apoptosis. Gene expression for inflammatory markers (interleukin [IL]-1β, IL-2, IL-4, IL-6, IL-10, tumour necrosis factor-alpha and interferon-gamma) was evaluated using polymerase chain reaction and myeloperoxidase assay for inflammation was performed.

Result

The use of refrigerant spray decreased vessel diameter and capillary density initially, although none of these decreases were statistically significant. Polymerase chain reaction showed no significant changes. The myeloperoxidase assay showed statistically significant increase in myeloperoxidase activity in groups 2, 3 and 4. Immunohistochemistry was negative for angiogenic and proinflammatory markers.

Conclusions

The lack of statistically significant changes in vessel diameter and inflammatory markers corroborated the safety on microcirculation.

Topical anaesthesia does not affect cutaneous vasomotor or sudomotor responses in human skin

(1) The effects of local sensory blockade (topical anaesthesia) on eccrine sweat glands and cutaneous circulation are not well understood. This study aimed to determine whether topical lidocaine/prilocaine alters eccrine sweat gland and cutaneous blood vessel responses. (2) Sweating (capacitance hygrometry) was induced via forearm intradermal microdialysis of five acetylcholine (ACh) doses (1 × 10(-4) to 1 × 10(0) m, 10-fold increments) in control and treated forearm sites in six healthy subjects. Nitric oxide-mediated vasodilatory (sodium nitroprusside) and adrenergic vasoconstrictor (noradrenaline) agonists were iontophoresed in lidocaine/prilocaine-treated and control forearm skin in nine healthy subjects during blood flow assessment (laser Doppler flowmetry, expressed as% from baseline cutaneous vascular conductance; CVC; flux/mean arterial pressure). (3) Non-linear regression curve fitting identified no change in the ED50 of ACh-induced sweating after sensory blockade (-1.42 ± 0.23 logM) compared to control (-1.27 ± 0.23 logM; P > .05) or in Emax (0.43 ± 0.08 with, 0.53 ± 0.16 mg cm(-2) min(-1) without lidocaine/prilocaine; P > .05). Sensory blockade did not alter the vasodilator response to sodium nitroprusside (1280 ± 548% change from baseline CVC with, 1204 ± 247% without lidocaine/prilocaine) or vasoconstrictor response to noradrenaline (-14 ± 4% change from baseline CVC with, -22 ± 14% without lidocaine/prilocaine; P > 0.05). (4) Cutaneous sensory blockade does not appear to alter nitric oxide-mediated vasodilation, adrenergic vasoconstriction, or cholinergic eccrine sweating dose-response sensitivity or responsiveness to maximal dose. Thus, lidocaine/prilocaine treatment should not affect sweat gland function or have blood flow implications for subsequent research protocols or clinical procedures.

The effect of a new topical local anaesthetic delivery system on forearm skin blood flow reactivity

Different topical local anaesthetics have varying effects on skin blood flow and vascular reactivity. We compared the vasoactive properties of Rapydan, a new topical local anaesthetic, with those of Ametop and EMLA creams in 20 healthy volunteers. Blood flow and vascular reactivity in the forearm skin were assessed by laser Doppler flowmetry and the transient hyperaemic response ratio respectively, before and after the application of EMLA (for 60 min), Ametop (for 30 and 60 min) and Rapydan (for 30 min). Application of EMLA had no effect on skin blood flow (median (IQR [range]) change from baseline -0.9% (-63 to 414 [-38.5 to 51.3] %, p = 1.0)) or mean (SD) transient hyperaemic response ratio (from 2.86 (0.86) to 3.17 (1.3), p = 0.38). The application of Ametop for 60 min produced a greater median (IQR [range]) increase in blood flow from baseline (508 (-55 to 998 [148-649]) %) than Rapydan applied for 30 min 160 (-77 to 997 [45-301]) %, p = 0.001), and a similar decrease in mean (SD) transient hyperaemic response ratio (from 2.69 (1.16) to 1.08 (0.26) and from 2.83 (0.84) to 1.49 (0.93) respectively, p = 0.57).