Search

The uptake, translocation, and metabolization of four widely used drugs, amitriptyline, orphenadrine, lidocaine, and tramadol, were investigated in a laboratory study. Cress (Lepidium sativum L.) and pea (Pisum sativum L.) were employed as model plants. These plants were grown in tap water containing the selected pharmaceuticals at concentrations ranging from 0.010 to 10 mg L -1 , whereby the latter concentration was employed for the (tentative) identification of drug-related metabolites formed within the plant. Thereby, mainly phase I metabolites were detected. Time-resolved uptake studies, with sampling after 1, 2, 4, 8, and 16 days, revealed that all four pharmaceuticals were taken up by the roots and further relocated to plant stem and leaves. Also in these studies, the corresponding phase I metabolites could be detected, and their translocation from root to stem (pea only) and finally leaves could be investigated., (© 2024. The Author(s).)

Preparation of drug metabolites at the milligram scale is essential for determining the structure and toxicity of drug metabolites. However, their preparation using recombinant proteins and human liver microsomes (HLM) is often difficult because of technical and ethical issues. Reproducing human drug metabolism in food-derived microorganisms may be useful for overcoming these challenges. In this study, we identified an unknown metabolite of the anaesthetic drug lidocaine, which is metabolised by HLM. By screening for lidocaine metabolic activity in five types of foods (blue cheese, shiitake mushroom, natto, yoghurt, and dry yeast), we found that bacteria isolated from natto reproduced the lidocaine metabolic reaction that occurs in HLM. A fraction containing the unknown lidocaine metabolite was prepared through mass cultivation of a Bacillus subtilis standard strain, ethyl acetate extraction, open column chromatography, and HPLC purification. We identified the unknown metabolite as 3-(2,6-dimethylphenyl)-1-ethyl-2-methyl-4-imidazolidinone using NMR. Our results showed that food-derived microorganisms can produce large amounts of human drug metabolites via large-scale cultivation. Additionally, food microorganisms that can reproduce drug metabolism in humans can be used to examine drug metabolites at a low cost and without ethical issues.

Drug-induced cardiotoxicity, a significant concern in the pharmaceutical industry, often results in the withdrawal of drugs from the market. The main cause of drug-induced cardiotoxicity is the use of immature cardiomyocytes during in vitro drug screening procedures. Over time, several methods such as topographical, conductive, and mechanical stimulation have been proposed to enhance both maturation and contractile properties of these cardiomyocytes. However, the synergistic effects of integrating topographical, conductive, and mechanical stimulation for cardiomyocyte maturation remain underexplored and poorly understood. To address this limitation, herein, we propose a grooved polydimethylsiloxane (PDMS) membrane embedded with silver nanowires (AgNWs-E-PDMS). The proposed AgNWs-E-PDMS membrane enhances the maturation of cardiomyocytes and provides a more accurate evaluation of drug-induced cardiotoxicity. When subjected to 10% tensile stress on the AgNWs-E-PDMS membrane, cardiomyocytes displayed substantial enhancements. Specifically, the contraction force, sarcomere length, and connexin-43 (Cx43) expression are increased by 2.0-, 1.5-, and 2.4-times, respectively, compared to the control state. The practical feasibility of the proposed device as a drug screening platform is demonstrated by assessing the adverse effects of lidocaine on cardiomyocytes. The contraction force and beat rate of lidocaine treated cardiomyocytes cultured on the AgNWs-E-PDMS membrane under mechanical stimulation decreased to 0.9 and 0.64 times their initial values respectively, compared to 0.6 and 0.51 times in the control state. These less pronounced changes in the contraction force and beat rate signify the superior drug response in the cardiomyocytes, a result of their enhanced maturation and growth on the AgNWs-E-PDMS membrane combined with mechanical stimulation.

The purpose of this study was to compare the extent of inflammation response in the middle carpal joints of healthy horses following intra-articular injection of 2% lidocaine, 0.5% bupivacaine, or 0.9% saline solution. The right middle carpal joint of 20 horses was injected with 5 mL of 0.5% bupivacaine (GB, n = 10) or 5 mL of 2% lidocaine (GL, n = 10). The left middle carpal joint of horses was used as a control (5 mL 0.9% saline). Serum and synovial fluid (SF) were aseptically collected before and at predetermined times after each injection. Serum and synovial fluid protein, albumin, transferrin, haptoglobin, ceruloplasmin, α1-antitripsin, and α1-acid glycoprotein concentrations were measured by sodium dodecyl sulfate polyacrylamide gel electrophoresis and compared among treatments. The results were submitted to analysis of variance using the SAS statistical program, and means were compared by the Student-Newman-Keuls test (P < .05). Both lidocaine and bupivacaine induced serum and SF changes indicative of inflammation, but the magnitude of those changes was more pronounced for lidocaine. Administration of 0.9% saline also induced an inflammatory reaction, but the magnitude of these changes was less pronounced than those caused by GB and GL. The results suggested that bupivacaine is safer than lidocaine for intra-articular injection in horses. Saline solution should not be used as an adjunct to intra-articular injections in horses., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Transdermal drug delivery has emerged as an alternative administration route for therapeutic drugs, overcoming current issues in oral and parenteral administration. However, this technology is hindered by the low permeability of the stratum corneum of the skin. In this work, we develop a synergic combination of two enhancing technologies to contribute to an improved and on-demand drug delivery through an iontophoretic system coupled with hollow microneedles (HMNs). For the first time, a polymeric HMN array coupled with integrated iontophoresis for the delivery of charged molecules and macromolecules ( e.g. proteins) is devised. To prove the concept, methylene blue, fluorescein sodium, lidocaine hydrochloride, and bovine serum albumin-fluorescein isothiocyanate conjugate (BSA-FITC) were first tested in an in vitro setup using 1.5% agarose gel model. Subsequently, the ex vivo drug permeation study using a Franz diffusion cell was conducted, exhibiting a 61-fold, 43-fold, 54-fold, and 17-fold increment of the permeation of methylene blue, fluorescein sodium, lidocaine hydrochloride, and BSA-FITC, respectively, during the application of 1 mA cm -2 current for 6 h. Moreover, the total amount of drug delivered ( i.e. in the skin and receptor compartment) was analysed to untangle the different delivery profiles according to the types of molecule. Finally, the integration of the anode and cathode into an iontophoretic hollow microneedle array system (IHMAS) offers the full miniaturisation of the concept. Overall, the IHMAS device provides a versatile wearable technology for transdermal on-demand drug delivery that can improve the administration of personalised doses, and potentially enhance precision medicine.

Abstract: The use of exogenous matrices has been described as an essential component in securing the viability and functionality of hepatocytes in vitro whether cultured for extracorporeal devices or cell transplantation. Here we report on the in vitro culture of porcine hepatocytes in polystyrene tissue-culture flasks without exogenous matrices showing adequate attachment and viability. Cell proliferation was evidenced by uptake of 5-bromo-2′-deoxyuridine, with peaks at Days 2 (19.7 ± 8.5%), 15 (20.8 ± 3.3%), and 35 (21.4 ± 0.3%). Detoxification capacity was assessed by determination of monoethylglycinexylidide, a product of lidocaine metabolism (highest value 156.5 ± 10.1 ng/ml at Day 4), and by diazepam clearance (maximum clearance 66.2% at Day 6). Diazepam metabolite levels were highest at Day 4 both for temazepam and oxazepam (6.5 ± 0.1 and 0.10 ± 0.01, respectively). These results suggest that the need for an exogenous matrix to achieve sustained proliferative activity and differentiated hepatocyte function should not necessarily be considered a sine qua non condition. [ABSTRACT FROM AUTHOR]

Background: Posttraumatic inflammation after joint injury, ranging from sprains to articular fracture, contributes to the development of arthritis, and the administration of interleukin 1 (IL-1) receptor antagonist (IL-1Ra) is a potential intervention to mitigate this response. Although IL-1Ra mitigates cartilage degenerative changes induced by IL-1, lidocaine is used for local pain management in acute joint injury. Intra-articular delivery of both drugs in combination would be a novel and possibly disease-modifying treatment. However, it is not known whether the interaction with lidocaine at clinical concentrations (1%) would alter the efficacy of IL-1Ra to protect cartilage from the catabolic effects of IL-1., Hypothesis: Treatment of articular cartilage with IL-1Ra in combination with a clinically relevant concentration of lidocaine (1%) will inhibit the catabolic effects of IL-1α in a manner similar to treatment with IL-1Ra alone., Study Design: Controlled laboratory study., Methods: Fresh porcine cartilage explants were harvested, challenged with IL-1α, and incubated for 72 hours with IL-1Ra or a combination of IL-1Ra and lidocaine. The primary outcome was total sulfated glycosaminoglycan (sGAG) release. Additional experiments assessed the effect of storage temperature and premixing of IL-1Ra and lidocaine on sGAG release. All explants were histologically assessed for cartilage degradation using a modified Mankin grading scale., Results: The combination of IL-1Ra and lidocaine, premixed at various time points and stored at room temperature or 4°C, was as effective as IL-1Ra alone at inhibiting IL-1α-mediated sGAG release. Mankin histopathology scores supported these findings., Conclusion: Our hypothesis was supported, and results indicated that the combination of IL-1Ra and lidocaine was as efficacious as IL-1Ra treatment alone in acutely mitigating biological cartilage injury due to IL-1α in an explant model., Clinical Significance: The combination of IL-1Ra and lidocaine is stable when reagents are stored in advance of administration at varying temperatures, providing clinically relevant information about storage of medications. The ability to premix and store this drug combination for intra-articular delivery may provide a novel treatment after joint injury to provide pain relief and block inflammation-induced catabolism of joint tissues.

Many studies suggest that animals exhibit lateralized behaviors during stressful situations. However, which brain structure in each hemisphere underlies such lateralized function is unclear. This study, investigated the effects of bilateral and unilateral inhibition of the ventral hippocampus (VH) on chronic restraint stress (CRS) induced memory impairment. Unilateral and bilateral VH cannulation was carried out. After a week of recovery, lidocaine hydrochloride was injected into the rat VH ten minutes before CRS induction for seven consecutive days. Behavioral (Y-maze and Morris water maze; MWM)), and histological (glial fibrillary acidic protein; GFAP, ionized calcium-binding adapter protein-1; Iba-1, as well as Golgi-Cox staining in the VH) studies were performed. The result showed no significant difference between the effect of right-only and left-only of VH inhibition induced by lidocaine on spatial learning and memory and working memory. In addition, lidocaine treated groups were significantly lower in spatial learning and memory and working memory than control groups during non-stress conditions. Furthermore, the dendritic arborization in the right-only, left-only and bilateral VH microinjected lidocaine significantly decreased after the CRS condition compared with the control group. However, lidocaine microinjection resulted in up-regulation levels of GFAP and Iba1 in the right-only, left-only and bilateral of VH and they were higher significantly than that of their control groups after CRS and during non-stress condition. Meanwhile, there is no significant difference between the effect of right-only and left-only of VH inhibition on neuronal arborization and glial cells during non-stress and after the CRS condition. In conclusion, bilateral VH inhibition can give rise to increase CRS-induced memory impairment. These findings were accompanied by elevating GFAP and Iba1 while reducing the dendritic arborization., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Porcine hepatocytes are used in the hybrid artificial liver support system that we are developing because of their high level of liver functions in vitro and because human hepatocytes can not be used in Japan for ethical reasons. Spherical multicellular aggregates or spheroids have been found to be effective in vitro for long-term maintenance of liver functions. Therefore, we formed spherical multicellular aggregates (spheroids) of primary porcine hepatocytes using a polyurethane foam (PUF) as a culture substratum and analyzed their drug metabolic functions in vitro. Primary porcine hepatocytes inoculated into the pores of a flat PUF plate (25 × 25 × 1 mm), spontaneously formed spheroids within the range of 100 to 150 μm in diameter 24 to 36 h after inoculation. The formed spheroids were attached to the bottom surface of the PUF pores, and their morphology and viability were maintained for more than 12 days. The P-450 activity in the spheroids of porcine hepatocytes was demonstrated by detecting production of monoethylglycinexylidide from lidocaine. In addition, the conjugation enzyme activity was demonstrated by detecting glucuronidation and sulfation of acetaminophen. These activities were maintained for 12 days at a level twice as high as in the monolayer culture. This result shows that the porcine hepatocyte spheroids formed by using PUF can maintain the drug metabolic functions important in a hybrid artificial liver device. Consequently, culturing porcine hepatocyte spheroids using PUF seems to be promising for development of a hybrid artificial liver. [ABSTRACT FROM AUTHOR]

Microneedles offer a convenient transdermal delivery route with potential for long term sustained release of drugs. However current microneedle technologies may not have the mechanical properties for reliable and stable penetration (e.g. hydrogel microneedles). Moreover, it is also challenging to realize microneedle arrays with large size and high flexibility. There is also an inherent upper limit to the amount and kind of drugs that can be loaded in the microneedles. In this paper, we present a new class of polymeric porous microneedles made from biocompatible and photo-curable resin that address these challenges. The microneedles are unique in their ability to load solid drug formulation in concentrated form. We demonstrate the loading and release of solid formulation of anesthetic and non-steroidal anti-inflammatory drugs, namely Lidocaine and Ibuprofen. Paper also demonstrates realization of large area (6 × 20 cm 2 ) flexible and stretchable microneedle patches capable of drug delivery on any body part. Penetration studies were performed in an ex vivo porcine model supplemented through rigorous compression tests to ensure the robustness and rigidity of the microneedles. Detailed release profiles of the microneedle patches were shown in an in vitro skin model. Results show promise for large area transdermal delivery of solid drug formulations using these porous microneedles., (© 2022. The Author(s).)

Voltage-gated sodium channels play a vital role in nerve and muscle cells, enabling them to encode and transmit electrical signals. Currently, there exist several classes of drugs that aim to inhibit these channels for therapeutic purposes, including local anesthetics, antiepileptics and antiarrhythmics. However, sodium-channel-inhibiting drugs lack subtype specificity; instead, they inhibit all sodium channels in the human body. Improving understanding of the mechanisms of binding of existing nonselective drugs is important in providing insight into how subtype-selective drugs could be developed. This study used molecular dynamics simulations to investigate the binding of the antiepileptics carbamazepine and lamotrigine and the local anesthetic lidocaine in neutral and charged states to the recently resolved human Nav1.4 channel. Replica exchange solute tempering was used to enable greater sampling of each compound within the pore. It was found that all four compounds show similarities in their binding sites within the pore. However, the positions of the carbamazepine and lamotrigine did not occlude the center of the pore but preferentially bound to homologous domain DII and DIII. The charged and neutral forms of lidocaine positioned themselves more centrally in the pore, with more common interactions with DIV. The best localized binding site was for charged lidocaine, whose aromatic moiety interacted with Y1593, whereas the amine projected toward the selectivity filter. Comparisons with our previous simulations and published structures highlight potential differences between tonic and use-dependent block related to conformational changes occurring in the pore., (Copyright © 2021 Biophysical Society. Published by Elsevier Inc. All rights reserved.)

Recently, lidocaine topical systems utilizing nonaqueous matrices have been developed and provide efficient lidocaine delivery through the skin, such that lower concentrations of drug provide equivalent or greater drug delivery than drug-in-matrix hydrogel lidocaine patches. This study characterizes drug delivery from a nonaqueous lidocaine topical system with increasing drug load both in vitro and in vivo. Topical systems formulated with either 1.8% or 5.4% lidocaine were applied to healthy volunteers' backs (n = 15) for 12 h in a single-center, open-label, four-treatment, four-period crossover pharmacokinetic study. Subjects were dosed with either three 1.8% systems or one, two, or three 5.4% systems in each period. Blood was collected for up to 48 h, and plasma lidocaine levels were measured with a validated HPLC method. In parallel, human and mouse skin models characterized the in vitro skin permeation profile. The pharmacokinetic profile was linear between one, two, and three lidocaine 5.4% applications. Application of three lidocaine 1.8% systems (108 mg lidocaine) was bioequivalent to one lidocaine 5.4% system (108 mg lidocaine). Both topical systems remained well adhered to the skin and irritation was mild. The 5.4% system had approximately threefold higher skin permeability than the 1.8% system in the mouse and human skin models. The results indicate increasing the drug load by three times results in triple the drug delivery both in vivo and in vitro. The relationship between the in vitro permeation and in vivo absorption correlates and is nonlinear., (© 2021. The Author(s).)

Lysosomes are critical for cellular metabolism and are heterogeneously involved in various cellular processes. The ability to measure lysosomal metabolic heterogeneity is essential for understanding their physiological roles. We therefore built a single-lysosome mass spectrometry (SLMS) platform integrating lysosomal patch-clamp recording and induced nano-electrospray ionization (nanoESI)/mass spectrometry (MS) that enables concurrent metabolic and electrophysiological profiling of individual enlarged lysosomes. The accuracy and reliability of this technique were validated by supporting previous findings, such as the transportability of lysosomal cationic amino acids transporters such as PQLC2 and the lysosomal trapping of lysosomotropic, hydrophobic weak base drugs such as lidocaine. We derived metabolites from single lysosomes in various cell types and classified lysosomes into five major subpopulations based on their chemical and biological divergence. Senescence and carcinoma altered metabolic profiles of lysosomes in a type-specific manner. Thus, SLMS can open more avenues for investigating heterogeneous lysosomal metabolic changes during physiological and pathological processes.

The use of pressure waves (PW) to disrupt the stratum corneum (SC) temporarily is an effective strategy to increase the deposition of drug molecules into the skin. However, given the rather modest outcomes when compared with ablation-assisted drug delivery, its potential has been underestimated. Accordingly, the aim of this study was to examine the impact of Resonant Amplitude Waves (RAWs) on increasing cutaneous delivery. RAW phenomena are triggered by focusing a high-peak-power pulsed laser onto an appropriate transducer structure, under space- and time-controlled resolution. In order to determine the optimal conditions for the generation and use of RAWs, a screening of laser parameters setting and an analysis of different geometries of the impact pattern over diverse materials used as transducers was performed, analyzing the footprint of the RAW waves in an agarose gel. The results obtained were then checked and fine-tuned using human skin samples instead of agarose. Furthermore, ex vivo experiments were carried out to characterize the effect of the RAWs in the cutaneous delivery of diclofenac (DIC) and lidocaine (LID) administered in the form of gels. The application of RAWs resulted in an increased delivery of DIC and LID to the skin, whose intensity was dependent on the composition of the formulation. In fact, the maximum observed for DIC and LID in short-time experiments (39.1 ± 11.1 and 153 ± 16 µg/cm 2 , respectively) was comparable to those observed using ablation-assisted drug delivery under the same conditions. In conclusion, the combination of RAWs with specific formulation strategies is a feasible alternative for the cutaneous delivery of drug candidates when short onset of action is required., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Intraoral lidocaine formulations are applied in children and adults for pain relief. The potential risks associated with orally administered lidocaine due to accidental ingestions were highlighted in a warning letter by the US Food and Drug Administration (FDA). This increases the urgency for a need of a child-appropriate dosage forms. For risk minimization, a novel buccal composite dosage form was developed consisting of a lidocaine containing minitablet centered on top of a bilayered mucoadhesive buccal film, so called composite. The preparation included direct tableting of minitablets as well as film-casting technique. Within a comparability study, the permeation of this composite was classified against marketed lidocaine gel, a single-layer film, and a minitablet. These ex-vivo permeation studies under physiologically related conditions in combination with LC-MS/MS quantification enabled the evaluation of permeation in clinically relevant short-term application. The composite showed comparable permeation to marketed gel (104.26 ± 30.15 µg/cm 2 vs 128.17 ± 12.49 µg/cm 2 cumulative amount of drug) and a higher permeation compared to film (25.84 ± 6.01 µg/cm 2 ). Therefore, a controlled drug application can be assumed by the composite, whereby the risk of inadvertent swallowing as well as uncontrolled absorbed amount of drug substance may be substantially minimized., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Lidocaine has cardiovascular and neurologic toxicity, which is dose-dependent. Due to CYP3A4-involved metabolism, lidocaine may be prone to drug-drug interactions., Materials and Methods: Given statins have the possibility of combination with lidocaine in the clinic, we established in vitro models to assess the effect of statins on the metabolism of lidocaine. Further pharmacokinetic alterations of lidocaine and its main metabolite, monoethylglycinexylidide in rats influenced by simvastatin, were investigated., Results: In vitro study revealed that simvastatin, among the statins, had the most significant inhibitory effect on lidocaine metabolism with IC 50 of 39.31 µM, 50 µM and 15.77 µM for RLM, HLM and CYP3A4.1, respectively. Consistent with in vitro results, lidocaine concomitantly used with simvastatin in rats was associated with 1.2-fold AUC (0-t) , 1.2-fold AUC (0-∞) , and 20%-decreased clearance for lidocaine, and 1.4-fold C max for MEGX compared with lidocaine alone., Conclusion: Collectively, these results implied that simvastatin could evidently inhibit the metabolism of lidocaine both in vivo and in vitro. Accordingly, more attention and necessary therapeutic drug monitoring should be paid to patients with the concomitant coadministration of lidocaine and simvastatin so as to avoid unexpected toxicity., Competing Interests: The authors report no conflicts of interest in this work., (© 2020 Wang et al.)

This work describes the characterization of an original liposomes/hydrogel assembly, and its application as a delayed-release system of antibiotics and anaesthetics. This system corresponds to drug-loaded liposomes entrapped within a chitosan (CS) physical hydrogel. To this end, a suspension of pre-formed 1,2-dipalmitoyl-sn-glycero-3-phosphocoline liposomes loaded with an antibiotic (rifampicin, RIF), an anaesthetic (lidocaine, LID), or a model fluorescent molecule (carboxyfluorescein, CF), was added to a CS solution. The CS gelation was subsequently carried out without any trace of chemical cross-linking agent or organic solvent in the final system. Liposomes within the resulting gelled CS matrix were characterized for the first time by environmental scanning electron microscopy. The release of drugs from the assembly was investigated by fluorescence or UV spectroscopy. The cumulative release profiles of RIF and LID (and also CF for comparison) were found to be lower from the "drug-in-liposomes-in-hydrogel" (DLH) assembly in comparison to "drug-in-hydrogel" (DH) system., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Though anesthetic drug delivery system and drug vehicles is generally applied for pain relief, there are have many difficulties and issues due to its short duration carrier and low biocompatibility, effectiveness at the conditions of inflammation at acidic pH. To resolve this issue, we have designed and developed the dual (pH and temperature) responsive bio-nanomaterial to improve the efficiency anesthetic drug delivery system. Chitosan is a unique class of biomaterials that is widely used in medical devices. The surface engineering of ZnFe 2 O 4 nanoparticles was performed by coating with chitosan using simple precipitation method. Then, multi-active anesthetic drug (Lidocaine) was loaded into nano-ferrite to form a drug delivery vehicle. The prepared drug-vesicle was characterized by using XRD, FTIR, SEM, XPS and TGA analysis. XRD analysis proved the face center cubic structure of zinc nanoferrite. The sustained delivery of Lidocaine (LDC) from CS coated nanoferrite (CS/ZnFe 2 O 4 ) was stimulated by pH and temperature responsive characteristics of vesicles. The in vitro cytotoxicity of the CS/ZnFe 2 O 4 particles towards fibroblast cells was analyzed by using MTT assay. The drug loaded CS/ZnFe 2 O 4 particles exhibit high biocompatibility and sustained drug release in the physiological pH environment (4.8, 5.5 and 7.4) and temperature responsive (25 and 37 °C) of normal tissues and also drug loading efficiency was measured., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The surface charge of brain endothelial cells forming the blood-brain barrier (BBB) is highly negative due to phospholipids in the plasma membrane and the glycocalyx. This negative charge is an important element of the defense systems of the BBB. Lidocaine, a cationic and lipophilic molecule which has anaesthetic and antiarrhytmic properties, exerts its actions by interacting with lipid membranes. Lidocaine when administered intravenously acts on vascular endothelial cells, but its direct effect on brain endothelial cells has not yet been studied. Our aim was to measure the effect of lidocaine on the charge of biological membranes and the barrier function of brain endothelial cells. We used the simplified membrane model, the bacteriorhodopsin (bR) containing purple membrane of Halobacterium salinarum and culture models of the BBB. We found that lidocaine turns the negative surface charge of purple membrane more positive and restores the function of the proton pump bR. Lidocaine also changed the zeta potential of brain endothelial cells in the same way. Short-term lidocaine treatment at a 10 μM therapeutically relevant concentration did not cause major BBB barrier dysfunction, substantial change in cell morphology or P-glycoprotein efflux pump inhibition. Lidocaine treatment decreased the flux of a cationic lipophilic molecule across the cell layer, but had no effect on the penetration of hydrophilic neutral or negatively charged markers. Our observations help to understand the biophysical background of the effect of lidocaine on biological membranes and draws the attention to the interaction of cationic drug molecules at the level of the BBB., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Topical administration is a preferable choice for local anesthetic delivery. Microemulsions have shown great effectiveness for transdermal transport of lidocaine. However, fabrication of microemulsions containing highly concentrated lidocaine (10%) to provide an extended local anesthetic effect is still a challenge. This study investigated the feasibility of using microemulsions for transdermal delivery of a high dosage of lidocaine (10%). At first, eutectic mixtures by kneading lidocaine with thymol were tailored to form a lipophilic solution, then the mixtures were readily incorporated into the oil phase of microemulsions after addition of proper surfactants and cosurfactants. The physicochemical properties, the skin permeation, local anesthetic efficacy, and the irritation experiment of the developed microemulsions were evaluated. The optimum composition was as follows: 12% of ethyl oleate as oil phase, 28% of the mixed surfactant, and cosurfactant (polyoxyl 15 hydroxystearate and ethanol) and 60% of the aqueous phase. The average particle size was about 13 nm. The transmission electron microscope (TEM) studies revealed almost homogeneous spherical globules without aggregation. The Fourier-transform infrared spectroscopy (FTIR) results highlighted the drugs homogeneously dispersed in the microemulsions. In vitro skin permeation and in vivo anesthesia effect evaluation indicated that microemulsions can enhance and extend the anesthetic effect of lidocaine. The irritable results indicated that the microemulsions had the better biocompatibility and the negligible influence on the dermal. Therefore, incorporating the eutectic mixtures into microemulsions could be proposed as an attractive choice and a promising transdermal delivery strategy for the future topical anesthetic therapy.

Purpose: Transdermal drug delivery of local anesthetics using lipid nanoparticles could enhance lipophilic drugs permeation through the stratum corneum, improve drug diffusion to deeper skin, and exert good therapeutic effects. The purpose of this study was to engineer a Tocopheryl Polyethylene Glycol 1000 Succinate (TPGS)-modified cationic nanostructured lipid carriers (NLC) for the delivery of lidocaine (LID; TPGS/LID-NLC)., Materials and Methods: TPGS/LID-NLC was prepared by solvent diffusion method. The particle size, polydispersity index, zeta potential, drug entrapment efficiency, drug loading, stability, drug release, and cytotoxicity were tested to evaluate the basic characters of NLC. In vitro skin permeation and in vivo anesthesia effect in an animal model were further investigated to determine the therapeutic efficiency of the system., Results: TPGS/LID-NLC had a particle size of 167.6±4.3 nm, a zeta potential of +21.2±2.3 mV, an entrapment efficiency of 85.9%±3.1%, and a drug loading of 11.5%±0.9%. A sustained release pattern was achieved by TPGS/LID-NLC, with 81.2% of LID released at 72 hours. In vitro permeation study showed that the steady-state fluxes (J ss ), permeability coefficient (Kp), and cumulative drug permeation Q n at 72 hours (Q 72 ) of TPGS/LID-NLC were 15.6±1.8 µg/cm 2 /hour, 10.3±0.9 cm/hour (×10 -3 ), and 547.5±23.6 µg/cm 2 , respectively, which were significantly higher than the nonmodified NLC and free drug groups. In vivo anesthesia effect of TPGS/LID-NLC was the most remarkable and long acting among the formulations tested, which could be concluded by the most considerable maximum possible effect from 10 to 120 minutes during the whole research., Conclusion: The most prominent in vitro permeation efficiency and in vivo anesthetic effect of TPGS/LID-NLC could be the evidence that TPGS-modified NLC could function as a promising drug delivery system for prolonged and efficient local anesthetic therapy., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Roberts and Rowland explained the well-stirred model as an extreme case of the dispersion model when the dispersion number is infinity. However, the inconsistency within and discrepancy between the theoretical explanation and experimental observations of the well-stirred model are discovered. In this paper, the well-stirred model is examined from both mathematical and physiological points of view. The well-stirred model is re-derived from the convection-elimination equation using the finite difference method. The well-stirred model is a subset of the parallel-tube model when the dispersion number is zero and concentration gradient is ignored. The relative errors and sensitivities of the well-stirred and the parallel-tube models are compared using numerical simulations. The well-stirred model should not be used to estimate in vivo apparent intrinsic clearance from hepatic extraction ratio for high extraction ratio drugs and predicting availability is not recommended for high extraction ratio drugs with either the well-stirred or the parallel-tube models. Based on our theoretical derivation and numerical simulations, we found lidocaine data analysis in Pang and Rowland's 1977 paper was based on an unfair comparison of these two models at two different efficiency number ranges. The high sensitivity of the parallel-tube model at a relatively lower efficiency number range versus the lack of sensitivity of the well-stirred model at an extremely high efficiency number range leads one to believe that the well-stirred model fit the data of high extraction ratio drugs such as lidocaine better. However, the intrinsic clearance values estimated by the parallel-tube model are much more consistent with both in vitro data and those estimated by the dispersion model than those by the well-stirred model. In addition, a key assumption used in the data analysis that the intrinsic clearance is independent of changes in blood flow may not be true. Both theoretical discussions and experimental results indicate that apparent intrinsic clearance and intrinsic clearance could be affected by blood flow and protein binding. Moreover, the lidocaine data analysis in 1977 paper could be control condition dependent and misleading when it is applied to data from other drugs, such as diazepam and diclofenac. The distinction between the well-stirred and parallel-tube models is a result of the mathematical treatment of concentration gradient rather than the flow pattern or extent of physical mixing. The well-stirred model is not likely better than the parallel-tube model. One should be cautious of using the well-stirred model for comparing in vitro intrinsic clearance and estimated in vivo "intrinsic clearance" for high clearance drugs., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Persistent pain remains a major health issue: common treatments relying on either repeated local injections or systemic drug administration are prone to concomitant side-effects. It is thought that an alternative could be a multifunctional cargo system to deliver medicine to the target site and release it over a prolonged time window. We nano-engineered microcapsules equipped with adjustable cargo release properties and encapsulated the sodium-channel blocker QX-314 using the layer-by-layer (LbL) technology. First, we employed single-cell electrophysiology to establish in vitro that microcapsule application can dampen neuronal excitability in a controlled fashion. Secondly, we used two-photon excitation imaging to monitor and adjust long-lasting release of encapsulated cargo in target tissue in situ. Finally, we explored an established peripheral inflammation model in rodents to find that a single local injection of QX-314-containing microcapsules could provide robust pain relief lasting for over a week. This was accompanied by a recovery of the locomotive deficit and the amelioration of anxiety in animals with persistent inflammation. Post hoc immunohistology confirmed biodegradation of microcapsules over a period of several weeks. The overall remedial effect lasted 10-20 times longer than that of a single focal drug injection. It depended on the QX-314 encapsulation levels, involved TRPV1-channel-dependent cell permeability of QX-314, and showed no detectable side-effects. Our data suggest that nano-engineered encapsulation provides local drug delivery suitable for prolonged pain relief, which could be highly advantageous compared to existing treatments.

Herein, reduced graphene oxide (RGO) has been utilized as an efficient sorbent in microextraction by packed sorbent (MEPS). The combination of MEPS and liquid chromatography-tandem mass spectrometry has been used to develop a method for the extraction and determination of three local anesthetics (i.e. lidocaine, prilocaine, and ropivacaine) in human plasma and saliva samples. The results showed that the utilization of RGO in MEPS could minimize the matrix effect so that no interfering peaks at the retention times of the analytes or internal standard was observed. The high extraction efficiency of this method was approved by mean recoveries of 97.26-106.83% and 95.21-105.83% for the studied analytes in plasma and saliva samples, respectively. Intra- and inter-day accuracies and precisions for all analytes were in good accordance with the international regulations. The accuracy values (as percentage deviation from the nominal value) of the quality control samples were between -2.1 to 13.9 for lidocaine, -4.2 to 11.0 for prilocaine and between -4.5 to -2.4 for ropivacaine in plasma samples while the values were ranged from -4.6 to 1.6 for lidocaine, from -4.2 to 15.5 for prilocaine and from -3.3 to -2.3 for ropivacaine in human saliva samples. Lower and upper limit of quantification (LLOQ, ULOQ) were set at 5 and 2000 nmol L -1 for all of the studied drugs. The correlation coefficients values were ≥0.995. The limit of detection values were obtained 4 nmol L -1 for lidocaine and prilocaine, and 2 nmol L -1 for ropivacaine., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Dexmedetomidine (DEX) is a sedative and analgesic agent that acts via the alpha-2 adrenoreceptor and is associated with reduced anesthetic requirements, as well as attenuated blood pressure and heart rate in response to stressful events. A previous study reported that cat gingival blood flow was controlled via sympathetic alpha-adrenergic fibers involved in vasoconstriction. In the present study, experiment 1 focused on the relationship between the effects of DEX on alpha adrenoreceptors and vasoconstriction in the tissues of the oral cavity and compared the palatal mucosal blood flow (PMBF) in rabbits between general anesthesia with sevoflurane and sedation with DEX. We found that the PMBF was decreased by DEX presumably because of the vasoconstriction of oral mucosal vessels following alpha-2 adrenoreceptor stimulation by DEX. To assess if this vasoconstriction would allow decreased use of locally administered epinephrine during DEX infusion, experiment 2 in the present study monitored the serum lidocaine concentration in rabbits to compare the absorption of lidocaine without epinephrine during general anesthesia with sevoflurane and sedation with DEX. The depression of PMBF by DEX did not affect the absorption of lidocaine. We hypothesize that this is because lidocaine dilates the blood vessels, counteracting the effects of DEX. In conclusion, despite decreased palatal blood flow with DEX infusion, local anesthetics with vasoconstrictors should be used in implant and oral surgery even with administered DEX.

Background and Objectives: Local anesthetics (LAs) are often infiltrated subcutaneously for localized perioperative numbing. In addition to blocking nerve conduction, LAs act on pathways used by a variety of pain-inducing and inflammatory mediators. We describe the effects in isolated model sensory neurons of LAs on responses to the algogenic and sensitizing peptide, bradykinin (BK)., Methods: ND/7 sensory neurons were stimulated by different concentrations of BK in the presence or absence of LAs, with transient increases in intracellular calcium (Δ[Ca]in) detected fluorometrically in fields of cells. Equilibrium saturable binding of radiolabeled BK also was conducted on the same type of cells, with and without LA., Results: Responses to low BK (5 nM) were inhibited by lidocaine at 1 mM (approximately 35% inhibition) and 10 mM (approximately 70% inhibition), whereas responses to high BK (100 nM) were unaffected by 1 mM yet inhibited (approximately 75%) by 10 mM lidocaine. Bupivacaine (1 and 2 mM) did not reduce peak Δ[Ca]in (using 5 nM BK). Lidocaine's quaternary derivative, QX-314 (10 mM), also was ineffective on peak Ca (5 nM BK). Saturation binding of BK showed that lidocaine lowered the binding capacity (Bmax) without changing the KD, consistent with noncompetitive inhibition., Conclusions: At subclinical concentrations, lidocaine suppresses BK's activation of model sensory neurons. This effect adds to the known analgesic mechanisms of LAs and likely contributes to the reduction of postincisional pain.

Local anesthetics are used for performing various regional anesthesia techniques to provide intraoperative anesthesia and analgesia, as well as for the treatment of acute and chronic pain. Older medications such as lidocaine and bupivacaine as well as newer ones such as mepivacaine and ropivacaine are being used successfully for decades. Routes of administration include neuraxial, perineural, intravenous, various infiltrative approaches, topical, and transdermal. There are new innovations with the use of older local anesthetics in a novel manner, in addition to the development and use of new formulations. This chapter seeks to summarize the pharmacokinetics of local anesthetics and address the role of newer local anesthetics, as well as clinical implications, safety profiles, and the future of local anesthetic research. Finally, some clinical pearls are highlighted., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Lidocaine, an amide anesthetic, has been used in the treatment of a wide variety of pain disorders for over 75 years. In addition to pain control, lidocaine is an anti-arrhythmic agent and has anti-inflammatory properties. Lidocaine's unique properties, including nonlinear pharmacokinetics, have limited its modern-day use., Objective: The purpose of this review is to offer a better understanding of the properties of this unique treatment, which we hope will allow more practitioners to offer this to their patients., Methods: An analysis of the history, pharmacokinetics, and relevant uses of lidocaine in headache medicine based on a synthesis of the medical literature and clinical experience., Results: Lidocaine is an amide anesthetic that inhibits voltage gated sodium channels, and lidocaine metabolism occurs exclusively in the liver. One lidocaine metabolite has its own unique properties and may be an active form of the drug., Conclusion: Open label and retrospective studies have investigated the use of lidocaine in many headache disorders, primarily via injection or infusion. Further research into the active metabolite of lidocaine may allow for its use as a novel nonopiate treatment of chronic pain., (© 2018 American Headache Society.)

The anaesthetic lidocaine is metabolised quickly to produce a series of metabolites, including several hydroxylated metabolites, which are further metabolised by addition of a glucuronic acid moiety. Analysis of these glucuronide metabolites in urine is performed indirectly by cleaving the glucuronic acid group using β-glucuronidase. However, direct analysis of intact glucuronide conjugates is a more straightforward approach as it negates the need for long hydrolysis incubations, and minimises the oxidation of sensitive hydrolysis products, while also distinguishing between the two forms of hydroxylated metabolites. A method was developed to identify three intact glucuronides of lidocaine in sheep urine using LC-MS/MS, which was further confirmed by the synthesis of glucuronide derivatives of 3OH-MEGX and 4OH-LIDO. Direct analysis of urine allowed the detection of the glucuronide metabolites of hydroxylidocaine (OH-LIDO), hydroxyl-monoethylglycinexylidide (OH-MEGX), and hydroxy-2,6-xylidine (OH-XYL). Analysis of urine before and after β-glucuronidase digestion showed that the efficiency of hydrolysis of these glucuronide metabolites may be underestimated in some studies. Analysis of urine in the current study from three different sheep with similar glucuronide metabolite concentrations resulted in different hydrolysis efficiencies, which may have been a result of different levels of substrate binding by matrix components, preventing enzyme cleavage. The use of direct analysis of intact glucuronides has the benefit of being less influenced by these matrix effects, while also allowing analysis of unstable metabolites like 4OH-XYL, which rapidly oxidises after hydrolysis. Additionally, direct analysis is less expensive and less time consuming, while providing more information about the status of hydroxylated metabolites in urine., (Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.)

The release of aromatic amines from drugs and other xenobiotics resulting from the hydrolysis of metabolically labile amide bonds presents a safety risk through several mechanisms, including geno-, hepato- and nephrotoxicity. Whilst multiple in vitro systems used for studying metabolic stability display serine hydrolase activity, responsible for the hydrolysis of amide bonds, they vary in their efficiency and selectivity. Using a range of amide-containing probe compounds (0.5-10 µM), we have investigated the hydrolytic activity of several rat, minipig and human-derived in vitro systems - including Supersomes, microsomes, S9 fractions and hepatocytes - with respect to their previously observed human in vivo metabolism. In our hands, human carboxylesterase Supersomes and rat S9 fractions systems showed relatively poor prediction of human in vivo metabolism. Rat S9 fractions, which are commonly utilised in the Ames test to assess mutagenicity, may be limited in the detection of genotoxic metabolites from aromatic amides due to their poor concordance with human in vivo amide hydrolysis. In this study, human liver microsomes and minipig subcellular fractions provided more representative models of human in vivo hydrolytic metabolism of the aromatic amide compounds tested.

Aim: Human cytochrome P450 3A4 is the most abundant isoform of P450 enzyme in the liver. It plays an important role in the metabolism of wide variety of xenobiotic and endogenous substrates. So far, there are few reports about the functional characterization of CYP3A4 variants in terms of specific substrates. The aim of this study was to systematically investigate the genetic polymorphisms of 23 CYP3A4 alleles and evaluate their catalytic activities on the metabolism of lidocaine in vitro., Methods and Results: The wild-type and 22 CYP3A4 variants were expressed in Spodoptera frugiperda 21 insect cells. Then the insect microsomes were incubated with the CYP3A4-specific substrate lidocaine. Reactions were performed with 50-3,000 µM for 60 min at 37°C. Lidocaine and its metabolite monoethylglycinexylidide were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry system. Of the 23 CYP3A4 allelic variants tested, 2 variants ( CYP3A4*17 and CYP3A4*30 ) had no detectable enzyme activity; and 5 variants ( CYP3A4*2 , CYP3A4*5 , CYP3A4*9 , CYP3A4*16 and CYP3A4*24 ) showed significantly decreased intrinsic clearance values compared with wild-type CYP3A4*1 ., Conclusion: As the first study of all these CYP3A4 alleles for lidocaine metabolism, our results in vitro assessment may provide novel insights into the allele-specific and substrate-specific activity of CYP3A4 and may also offer a reference to the personalized treatment of lidocaine in a clinical setting., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Since a significant proportion of diabetic patients have clinical or subclinical neuropathy, there may be concerns about the use of local anaesthetics. The present study was designed to determine and compare the effects of articaine, a widely used anaesthetic in dental practice, and lidocaine on the resting and axonal stimulation-evoked release of [ 3 H]noradrenaline ([ 3 H]NA) in prefrontal cortex slices and the release of [ 3 H]NA in spinal cord slices prepared from non-diabetic and streptozocin (STZ)-induced diabetic (glucose level=22.03±2.31mmol/l) rats. The peak of allodynia was achieved 9 weeks after STZ-treatment. Articaine and lidocaine inhibited the stimulation-evoked release in a concentration-dependent manner and increased the resting release by two to six times. These effects indicate an inhibitory action of these anaesthetics on Na + - and K + -channels. There was no difference in clinically important nerve conduction between non-diabetic and diabetic rats, as measured by the release of transmitter in response to axonal stimulation. The uptake and resting release of NA was significantly higher in the brain slices prepared from diabetic rats, but there were no differences in the spinal cord. For the adverse effects, the effects of articaine on K + channels (resting release) are more pronounced compared to lidocaine. In this respect, articaine has a thiophene ring with high lipid solubility, which may present potential risks for some patients., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

OBJECTIVE To quantify nausea and sedation scores, gastric emptying time, and gastrointestinal transit time after IV administration of a lidocaine hydrochloride bolus followed by a constant rate infusion (CRI) in clinically normal dogs. ANIMALS 6 Beagles. PROCEDURES In a crossover study, dogs were fed thirty 1.5-mm barium-impregnated spheres (BIPS) and received a saline (0.9% NaCl) solution bolus (0.05 mL/kg) IV (time 0) followed by a CRI at 10 mL/h, a lidocaine bolus (1 mg/kg) IV followed by a CRI at 25 μg/kg/min, or a lidocaine bolus (1 mg/kg) IV followed by a CRI at 50 μg/kg/min; CRIs were for 12 hours. Nausea and sedation scores were assessed and abdominal radiographs obtained immediately after feeding of BIPS and every hour for 12 hours and again 16 hours after CRI start. Percentage of BIPSs in the small and large intestines, gastric emptying time, and gastrointestinal transit time were assessed. RESULTS Gastric emptying time did not differ significantly among treatments. Significantly more BIPS were in the large intestine 4 to 7 hours after treatment start for the 50-μg/kg/min treatment than for the other 2 treatments. Six hours after treatment start, significantly more BIPS were in the large intestine for the 25-μg/kg/min treatment than for the saline solution treatment. Higher sedation and nausea scores were associated with the 50-μg/kg/min CRI. CONCLUSIONS AND CLINICAL RELEVANCE In clinically normal dogs, lidocaine CRI did not significantly affect gastric emptying. However, gastrointestinal transit time was mildly decreased and sedation and nausea scores increased in dogs administered a lidocaine CRI at clinically used doses.

1. Topical anesthesia with benzocaine or lidocaine occasionally causes methemoglobinemia, an uncommon but potentially fatal disorder where the blood has a reduced ability to transport oxygen. Previous in vitro studies using human whole blood have shown that benzocaine causes more methemoglobin (MetHb) formation than lidocaine, and that both compounds require metabolic transformation to form the MetHb producing species. In the current investigation, the active species of benzocaine forming the MetHb was investigated. 2. HPLC analysis of benzocaine samples incubated with human hepatic S9 showed the formation of a peak with the same UV spectrum and retention time as benzocaine hydroxylamine (BenzNOH). To confirm the activity of BenzNOH, MetHb production following exposure to the compound was determined in whole human blood using an Avoximeter 4000 CO-oximeter. 3. BenzNOH produced MetHb in a concentration dependent manner without the need for metabolic activation. Benzocaine in the presence of metabolic activation required a concentration of 500 μM to produce a similar degree of MetHb formation as 20 μM BenzNOH without activation. Previous work suggested that two metabolites of lidocaine may also form MetHb; N-hydroxyxylidine and 4-hydroxyxylidine. Of these two metabolites 4-hydroxyxylidine produced the most MetHb in whole blood in vitro in the absence of metabolic activation, however BenzNOH produced up to 14.2 times more MetHb than 4-hydroxyxylidine at a similar concentration. 4. These results suggest that the ability of benzocaine to form MetHb is likely to be mediated through its hydroxylamine metabolite and that this metabolite is inherently more active than the potentially MetHb-forming metabolites of lidocaine.

Lidocaine is known to inhibit the hyperpolarization-activated mixed cation current (I h ) in cardiac myocytes and neurons, as well in cells transfected with cloned Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channels. However, the molecular mechanism of I h inhibition by this drug has been limitedly explored. Here, we show that inhibition of I h by lidocaine, recorded from Chinese hamster ovary (CHO) cells expressing the HCN1 channel, reached a steady state within one minute and was reversible. Lidocaine inhibition of I h was greater at less negative voltages and smaller current amplitudes whereas the voltage-dependence of I h activation was unchanged. Lidocaine inhibition of I h measured at -130 mV (a voltage at which I h is fully activated) was reduced, and I h amplitude was increased, when the concentration of extracellular potassium was raised to 60 mM from 5.4 mM. By contrast, neither I h inhibition by the drug nor I h amplitude at +30 mV (following a test voltage-pulse to -130 mV) were affected by this rise in extracellular potassium. Together, these data indicate that lidocaine inhibition of I h involves a mechanism which is antagonized by hyperpolarizing voltages and current flow.

This study showed that drug-coated PLLA (Poly (L-lactide)) microneedle arrays can induce rapid and painless local anesthesia. Microneedle arrays were fabricated using a micro-molding technique, and the needle tips were coated with 290.6 ± 45.9 μg of lidocaine, the most widely used local anesthetic worldwide. A dip-coating device was newly designed for the coating step using an optimized coating formulation. Lidocaine coated on the arrays was released rapidly into PBS within 2 min, and its stability in storage lasted 3 weeks at 4, 25, and 37°C. Furthermore, the microneedle arrays showed consistent in vitro skin penetration and delivered 200.8 ± 43.9, 224.2 ± 39.3, and 244.1 ± 19.6 μg of lidocaine into the skin 1, 2, and 5 min after application with a high delivery efficiency of 69, 77, and 84%. Compared to a commercially available topical anesthetic EMLA® cream, a 22.0, 13.6, and 14.0-fold higher amount of lidocaine was delivered into the skin. Note, in vitro skin permeation of Lidocaine was also notably enhanced by a 2-min-application of the lidocaine-coated microneedle arrays. Altogether, these results suggest that the biocompatible lidocaine-coated PLLA microneedle arrays could provide significantly rapid local anesthesia in a painless manner without any of the issues from topical applications or hypodermic injections of local anesthetics.

Mefloquine constitutes a multitarget antimalaric that inhibits cation currents. However, the effect and the binding site of this compound on Na + channels is unknown. To address the mechanism of action of mefloquine, we employed two-electrode voltage clamp recordings on Xenopus laevis oocytes, site-directed mutagenesis of the rat Na + channel, and a combined in silico approach using Molecular Dynamics and docking protocols. We found that mefloquine: i) inhibited Na v 1.4 currents (IC 50 =60μM), ii) significantly delayed fast inactivation but did not affect recovery from inactivation, iii) markedly the shifted steady-state inactivation curve to more hyperpolarized potentials. The presence of the β1 subunit significantly reduced mefloquine potency, but the drug induced a significant frequency-independent rundown upon repetitive depolarisations. Computational and experimental results indicate that mefloquine overlaps the local anaesthetic binding site by docking at a hydrophobic cavity between domains DIII and DIV that communicates the local anaesthetic binding site with the selectivity filter. This is supported by the fact that mefloquine potency significantly decreased on mutant Na v 1.4 channel F1579A and significantly increased on K1237S channels. In silico this compound docked above F1579 forming stable π-π interactions with this residue. We provide structure-activity insights into how cationic amphiphilic compounds may exert inhibitory effects by docking between the local anaesthetic binding site and the selectivity filter of a mammalian Na + channel. Our proposed synergistic cycle of experimental and computational studies may be useful for elucidating binding sites of other drugs, thereby saving in vitro and in silico resources., (Copyright © 2016 Elsevier B.V. All rights reserved.)

UV imaging is capable of providing spatially and temporally resolved absorbance measurements, which is highly beneficial in drug diffusion, dissolution and release testing studies. For optimal planning and design of experiments, knowledge about the capabilities and limitations of the imaging system is required. The aim of this study was to characterize the performance of two commercially available UV imaging systems, the D100 and SDI. Lidocaine crystals, lidocaine containing solutions, and gels were applied in the practical assessment of the UV imaging systems. Dissolution of lidocaine from single crystals into phosphate buffer and 0.5% (w/v) agarose hydrogel at pH 7.4 was investigated to shed light on the importance of density gradients under dissolution conditions in the absence of convective flow. In addition, the resolution of the UV imaging systems was assessed by the use of grids. Resolution was found to be better in the vertical direction than the horizontal direction, consistent with the illumination geometry. The collimating lens in the SDI imaging system was shown to provide more uniform light intensity across the UV imaging area and resulted in better resolution as compared to the D100 imaging system (a system without a lens). Under optimal conditions, the resolution was determined to be 12.5 and 16.7 line pairs per mm (lp/mm) corresponding to line widths of 40μm and 30μm in the horizontal and vertical direction, respectively. Overall, the performance of the UV imaging systems was shown mainly to depend on collimation of light, the light path, the positioning of the object relative to the line of 100μm fibres which forms the light source, and the distance of the object from the sensor surface., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Mammalian flavin-containing monooxygenases, which are difficult to obtain and study, play a major role in detoxifying various xenobiotics. To provide alternative biocatalytic tools to generate flavin-containing monooxygenases (FMO)-derived drug metabolites, a collection of microbial flavoprotein monooxygenases, sequence-related to human FMOs, was tested for their ability to oxidize a set of xenobiotic compounds. For all tested xenobiotics [nicotine, lidocaine, 3-(methylthio)aniline, albendazole, and fenbendazole], one or more monooxygenases were identified capable of converting the target compound. Chiral liquid chromatography with tandem mass spectrometry analyses of the conversions of 3-(methylthio)aniline, albendazole, and fenbendazole revealed that the respective sulfoxides are formed in good to excellent enantiomeric excess (e.e.) by several of the tested monooxygenases. Intriguingly, depending on the chosen microbial monooxygenase, either the (R)- or (S)-sulfoxide was formed. For example, when using a monooxygenase from Rhodococcus jostii the (S)-sulfoxide of albendazole (ricobendazole) was obtained with a 95% e.e. whereas a fungal monooxygenase yielded the respective (R)-sulfoxide in 57% e.e. For nicotine and lidocaine, monooxygenases could be identified that convert the amines into their respective N-oxides. This study shows that recombinantly expressed microbial monooxygenases represent a valuable toolbox of mammalian FMO mimics that can be exploited for the production of FMO-associated xenobiotic metabolites., (Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.)

Context: Intraoral drug delivery as mucosal delivery pathway provides a huge platform in the pharmaceutical field., Objective: Combining mucoadhesiveness and controlled release of thio-poly acrylic acid as advanced excipient for buccal drug delivery., Materials and Methods: Mediated by carbodiimide, cysteine was covalently attached to poly acrylic acid. This thiomer was assessed with regard to cytotoxicity, stability, mucoadhesion, and rheology as well as release behavior of Lidocaine., Results: Stability assays of thio-poly acrylic acid were complying with United States Pharmacopeia requirements. Mucoadhesion assay such as tensile (total work of adhesion), bioadhesion, rotating cylinder revealed as this thiomer was superior in comparison to non-thiolated poly acrylic acid with 7.61-fold, 2.8-fold, 5.61-fold improvement, respectively without any toxic effect. The cell viability exhibited over 90% after incubation time of 3 h and 24 h respectively. Lidocaine release showed 1.98-fold more controlled release over 3 h in comparison to unmodified poly acrylic acid., Conclusion: Taken the findings in consideration, thio-poly acrylic acid provides excellent stability, controlled release, and superior mucoadhesive features. The prolonged residence time of thio-poly acrylic acid represents a pillar in the buccal drug delivery.

Background: Inward rectifier K channels of the Kir2.x subfamily are widely expressed in neuronal tissues, controlling neuronal excitability. Previous studies reported that local anesthetics (LAs) do not affect Kir2 channels. However, the effects have not been studied at large concentrations used in regional anesthesia., Methods: This study used the patch-clamp technique to examine the effects of bupivacaine and lidocaine on Kir2.1, Kir2.2, and Kir2.3 channels expressed in human embryonic kidney 293 cells., Results: When applied extracellularly in whole-cell recordings, both LAs inhibited Kir2.x currents in a voltage-independent manner. Inhibition with bupivacaine was slow and irreversible, whereas that with lidocaine was fast and reversible. Kir2.3 displayed a greater sensitivity to bupivacaine than Kir2.1 and Kir2.2 (50% inhibitory concentrations at approximately 5 minutes, 0.6 vs 8-10 mM), whereas their sensitivities to lidocaine were similar (50% inhibitory concentrations, 1.5-2.7 mM). Increases in the charged/neutral ratio of the LAs at an acidic extracellular pH attenuated their inhibitory effects, and a permanently charged lidocaine derivative QX-314 exhibited no effects when applied extracellularly. Inside-out experiments demonstrated that inhibition of Kir2.1 with cytoplasmic lidocaine and QX-314 was rapid and reversible, whereas that induced by bupivacaine was slow and irreversible. Furthermore, dose-inhibition relations for the charged form of bupivacaine and lidocaine obtained at different cytoplasmic pHs could be approximated by a single relation for each LA., Conclusions: The results indicate that both LAs at clinical concentrations equilibrated rapidly with the intracellular milieu, differentially inhibiting Kir2.x channel function from the cytoplasmic side.

The objective of the present study was to investigate the influence of preparation and storage conditions on the histology and permeability of different parts of porcine oral mucosa used for in vitro studies of transbuccal formulations. Fresh and frozen (-20°C and -80°C, with or without cryoprotectant) epithelia of porcine palatal, gingival, dorsum of the tongue, and buccal mucosa were submitted for histological analyses to determine the effects of storage conditions on barrier integrity. Permeation of lidocaine hydrochloride (used as a hydrophilic model drug) across fresh and previously frozen oral epithelium was measured in order to evaluate the barrier function. Histological evaluation demonstrated that the oral epithelium was successfully separated from the connective tissue, except for gingival mucosa. After storage under different conditions, all tissues presented desquamation of superficial layers and spherical spaces induced by the freezing process. The permeability of lidocaine hydrochloride varied among the fresh oral mucosa and generally increased after freezing. In conclusion, fresh epithelium from the buccal and dorsum of the tongue mucosa should be used for in vitro studies investigating hydrophilic drug transport when these are the desired clinical application sites. However, when the palate is the target site, both fresh and frozen (for up to 4weeks, without addition of cryoprotectant) samples could be used. The addition of glycerol as a cryoprotectant should be avoided due to increased lidocaine hydrochloride permeability., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Iontophoresis is the noninvasive delivery of ions using direct current. The direct current has some disadvantages such as skin burning. Interferential current is a kind of alternating current without limitations of direct current; so the purpose of this study is to investigate and compare the effects of lidocaine, interferential current and lidocaine iontophoresis using interferential current. 30 healthy women aged 20-24 years participated in this randomized clinical trial study. Pressure, tactile and pain thresholds were evaluated before and after the application of treatment methods. Pressure, tactile and pain sensitivity increased significantly after the application of lidocaine alone (p < 0.005) and lidocaine iontophoresis using interferential current (p < 0.0001). Lidocaine iontophoresis using interferential current can increase perception threshold of pain, tactile stimulus and pressure sense more significantly than lidocaine and interferential current alone.

Voltage-gated Na(+) channels (VGSCs) initiate action potentials thereby giving rise to rapid transmission of electrical signals along cell membranes and between cells. Depolarization of the cell membrane causes VGSCs to open but also gives rise to a nonconducting state termed inactivation. Inactivation of VGSCs serves a critical physiologic function as it determines the extent of excitability of neurons and of muscle cells. Depending on the time course of development and removal of inactivation both "fast-" and "slow"-inactivated states have been described. Evidence from mutagenesis studies suggests that fast inactivation is produced by a block of the internal vestibule by a tethered inactivation particle that has been mapped to the internal linker between domains III and IV. The motion of this linker may be regulated by parts of the internal C-terminus. The molecular mechanism of slow inactivation is less clear. However, aside from a high number of mutagenesis studies, the recent availability of 3D structures of crystallized prokaryotic VGSCs offers insights into the molecular motions associated with slow inactivation. One possible scenario is that slow movements of the voltage sensors are transmitted to the external vestibule giving rise to a conformational change of this region. This molecular rearrangement is transmitted to the S6 segments giving rise to collapse of the internal vestibule., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Lidocaine hydrochloride ophthalmic gel is a novel ophthalmic preparation for topical ocular anesthesia. The study is aimed at evaluating the ocular and systemic pharmacokinetics of lidocaine hydrochloride 3.5 % ophthalmic gel in rabbits after ocular topical administration. Thirty-six rabbits were randomly placed in 12 groups (3 rabbits per group). The rabbits were quickly killed according to their groups at 0 (predose), 0.0833, 0.167, 0.333, 0.667, 1, 1.5, 2, 3, 4, 6, and 8 h postdose and then the ocular tissue and plasma samples were collected. All the samples were analyzed by a validated LC-MS/MS method. The test result showed that the maximum concentration (C max) of lidocaine in different ocular tissues and plasma were all achieved within 20 min after drug administration, and the data of C max were (2,987 ± 1814) μg/g, (44.67 ± 12.91) μg/g, (26.26 ± 7.19) μg/g, (11,046 ± 2,734) ng/mL, and (160.3 ± 61.0) ng/mL for tear fluid, cornea, conjunctiva, aqueous humor, and plasma, respectively. The data of the elimination half-life in these tissues were 1.5, 3.2, 3.5, 1.9, and 1.7 h for tear fluid, cornea, conjunctiva, aqueous humor, and plasma, respectively. The intraocular lidocaine levels were significantly higher than that in plasma, and the elimination half-life of lidocaine in cornea, conjunctiva, and aqueous humor was relatively longer than that in tear fluid and plasma. The high intraocular penetration, low systemic exposure, and long duration in the ocular tissues suggested lidocaine hydrochloride 3.5 % ophthalmic gel as an effective local anesthetic for ocular anesthesia during ophthalmic procedures.

Taking EMLA cream and Penles tape 18 mg as examples, this article describes the conditions for skin penetration of topical anesthetics, with their onset time of action, duration of effect and a precautions for their use. EMLA cream is a unique cream for topical anesthesia which is the eutectic mixture of lidocaine and propitocaine to increase skin penetration. The safety study demonstrated that blood concentrations of active ingredients of EMLA cream were below toxic levels. EMLA cream, with confirmed high skin penetrability and safety, should be used for pain reduction of various treatments for many diseases. Here in Japan, EMLA cream has indications not only for pain reduction of skin laser therapy but also for reduction of needle puncture pain. This means the use of topical anesthesia would be expanded to wider ranges of treatments.

Background: Lidocaine has been widely used to relieve acute pain and chronic refractory pain effectively by both systemic and local administration. Numerous studies reported that lidocaine affects several pain signaling pathways as well as voltage-gated sodium channels, suggesting the existence of multiple mechanisms underlying pain relief by lidocaine. Some extracellular adenosine triphosphate (ATP) receptor subunits are thought to play a role in chronic pain mechanisms, but there have been few studies on the effects of lidocaine on ATP receptors. We studied the effects of lidocaine on purinergic P2X3, P2X4, and P2X7 receptors to explore the mechanisms underlying pain-relieving effects of lidocaine., Methods: We investigated the effects of lidocaine on ATP-induced currents in ATP receptor subunits, P2X3, P2X4, and P2X7 expressed in Xenopus oocytes, by using whole-cell, two-electrode, voltage-clamp techniques., Results: Lidocaine inhibited ATP-induced currents in P2X7, but not in P2X3 or P2X4 subunits, in a concentration-dependent manner. The half maximal inhibitory concentration for lidocaine inhibition was 282 ± 45 μmol/L. By contrast, mepivacaine, ropivacaine, and bupivacaine exerted only limited effects on the P2X7 receptor. Lidocaine inhibited the ATP concentration-response curve for the P2X7 receptor via noncompetitive inhibition. Intracellular and extracellular N-(2,6-dimethylphenylcarbamoylmethyl) triethylammonium bromide (QX-314) and benzocaine suppressed ATP-induced currents in the P2X7 receptor in a concentration-dependent manner. In addition, repetitive ATP treatments at 5-minute intervals in the continuous presence of lidocaine revealed that lidocaine inhibition was use-dependent. Finally, the selective P2X7 receptor antagonists Brilliant Blue G and AZ11645373 did not affect the inhibitory actions of lidocaine on the P2X7 receptor., Conclusions: Lidocaine selectively inhibited the function of the P2X7 receptor expressed in Xenopus oocytes. This effect may be caused by acting on sites in the ion channel pore both extracellularly and intracellularly. These results help to understand the mechanisms underlying the analgesic effects of lidocaine when it is administered locally at least.