Discovery of a Novel Lidocaine Metabolite by Human Liver Microsome and Identification of Microbial Species Which Produces the Same Metabolite.

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.

A Bilayer Microneedle for Modulated Sequential Release of Adrenaline and Lidocaine for Prolonged Local Anesthesia.

Chronic pain emerges as a major global health issue, significantly impacting individuals' health and quality of life. In this study, we designed a bilayer microneedle loaded with lidocaine nanocomposites in the inner layer and adrenaline (Adr) in the outer layer (HCP MNs) for modulated sequential release to achieve prolonged local anesthesia. The obtained HCP MNs featured an intact structure with adequate mechanical strength for efficient skin penetration. The bilayer structure of MNs was evidenced by loading two fluorescent dyes in each layer. Furthermore, these HCP MNs were capable of inducing rapid as well as prolonged local anesthetic effects in guinea pigs. Hence, the bilayer MN coloaded with Adr and lidocaine nanocomposite serves as a promising transdermal delivery platform for chronic pain management.

An isocratic RP-HPLC-UV method for simultaneous quantification of tizanidine and lidocaine: application to in vitro release studies of a subcutaneous implant.

Implantable devices have been widely investigated to improve the treatment of multiple diseases. Even with low drug loadings, these devices can achieve effective delivery and increase patient compliance by minimizing potential side effects, consequently enhancing the quality of life of the patients. Moreover, multi-drug products are emerging in the pharmaceutical field, capable of treating more than one ailment concurrently. Therefore, a simple analytical method is essential for detecting and quantifying different analytes used in formulation development and evaluation. Here, we present, for the first time, an isocratic method for tizanidine hydrochloride (TZ) and lidocaine (LD) loaded into a subcutaneous implant, utilizing reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with a UV detector. These implants have the potential to treat muscular spasticity while providing pain relief for several days after implantation. Chromatographic separation of the two drugs was accomplished using a C18 column, with a mobile phase consisting of 0.1% TFA in water and MeOH in a 58 : 42 ratio, flowing at 0.7 ml min-1. The method exhibited specificity and robustness, providing accurate and precise results. It displayed linearity within the range of 0.79 to 100 µg ml-1, with an R2 value of 1 for the simultaneous analysis of TZ and LD. The developed method demonstrated selectivity, offering limits of detection and quantification of 0.16 and 0.49 µg ml-1 for TZ, and 0.30 and 0.93 µg ml-1 for LD, respectively. Furthermore, the solution containing both TZ and LD proved stable under various storage conditions. While this study applied the method to assess an implant device, it has broader applicability for analysing and quantifying the in vitro drug release of TZ and LD from diverse dosage forms in preclinical settings.

A simple, fast, and cost-effective smartphone-based digital imaging method for quantification of lidocaine hydrochloride in pharmaceutical formulations.

OBJECTIVE: A simple, highly specific, accurate and fast method by smartphone-based digital imaging was developed for estimating lidocaine hydrochloride in pharmaceutical formulations. MATERIAL AND METHODS: To obtain the images, a Galaxy A03 Core smartphone and an image acquisition device developed in the laboratory were used to control the incident factors in reproducibility of the measurements. The processing of the images was carried out with the Color Grab application. Finally, the absorbance values were calculated using the RGB intensity values of blank, standard, and sample solutions. The proposed method was compared with spectroscopic and chromatographic methods. RESULTS: The reaction between copper and lidocaine hydrochloride was characterized, showing better results in an equimolar ratio and maintaining the pH of the solution above 11.5. The use of the device for the capture of digital images allowed to control those sensitive parameters for reproducibility so that the analytical measurements showed adequate precision and accuracy. Validation of the main parameters of the method showed compliance with acceptance criteria. The application of the method for the analysis of injectable samples achieved reliable results, which were statistically similar to other reference instrumental methods. CONCLUSION: The proposed method presented figures of merit in relation to linearity, precision, selectivity, accuracy, and robustness; it was carried out by designing and manufacturing a device for capturing digital images on a smartphone, which were analyzed to obtain RGB intensity values. These data are finally used to calculate absorbance values of solutions. All these elements provide this work with innovative characteristics in the field of analysis for control of pharmaceutical formulations.

Quantitative chromatographic method development for residual lidocaine in topical systems and biological samples.

Background: The aim of this work was to develop and validate sensitive and efficient analytical methods for estimating systemic drug exposure and residual drug following the application of topical delivery systems. Materials & methods: Lidocaine was extracted using a liquid-liquid extraction technique from commercial topical products and analyzed using ultra high-performance liquid chromatography. A separate LC-MS/MS method was developed for analyzing human serum samples. Results & conclusion: The developed methods were successfully applied for estimating lidocaine content in two commercial products demonstrating 97.4-104.0% for product A and 105.0-110.7% for product B. The LC-MS/MS method displayed successful analysis of lidocaine from human serum samples. The developed methods are recommended for quantifying systemic exposure and residual drug analysis of topical systems.

Nanoparticulate System Based on Calcium-Crosslinked Carbomer Retards Percutaneous Drug Permeation: New Insight Into Skin Barrier Functions.

BACKGROUND: The stratum corneum poses a formidable barrier for dermal and transdermal delivery of drugs. Besides the stratum corneum barrier, the viable epidermis poses another challenge to pharmaceutical formulators. A drug is probably transdermally permeable if it rapidly crosses the epidermal secondary barrier, while stimulation of lamellar body secretion from granular cells and intracellular release of Ca++ from endoplasmic reticulum (ER) result in retardation. OBJECTIVE: To evaluate the skin permeability of lidocaine HCl loaded in nanoparticles made of carbomer calcified with calcium gluconate, while figuring out the physiological mechanism that regulates the Ca++ related skin barrier function. METHODS: Lidocaine hydrochloride was loaded in a nanoparticulate system based on calcified carbomer, fabricated by using a water-in-oil microemulsion as a precursor. In vitro release and percutaneous permeation testing were carried out to compare between calcified and non-calcified nanoparticles. In addition, comparison was also made between calcified nanoparticles using carbomer gels prepared at two pH values and at two different ratios of Ca++/carbomer. RESULTS: A unique structure of the calcified nanoparticles has been proposed, in which the carbomer nanoparticles are partially coated by gluconate ions through hydrogen bonding and partially through ionic interactions with calcium ions. Although the in vitro release data showed no difference between non-calcified and calcified carbomer nanoparticles, a calcium-related phenomenon of skin retardation has been revealed. CONCLUSIONS: It has been proposed that stimulation of lamellar body secretion from granular cells and Ca++ release from ER, which is elicited by the calcium gluconate-coated nanoparticles, result in dermal retardation of lidocaine.

Impact of the Dicarboxylic Acid Chain Length on Intermolecular Interactions with Lidocaine.

Acid-base multicomponent systems have become a popular choice as a strategy to fine-tune the physicochemical properties of active pharmaceutical ingredients. Current prediction tools based on the principles of anticrystal engineering cannot always accurately predict the nature of intermolecular interactions within a multicomponent system. Even small changes in the physicochemical parameters of parent components can result in unexpected outcomes, and many salt, cocrystal, and ionic liquid forms are still being discovered empirically. In this work, we aimed to establish structural consistency in a series of mixtures comprising lidocaine (LID) with decanedioic, undecanedioic, dodecanedioic, and tridecanedioic acids and to explore how length and flexibility of the acid carbon backbone affect the molecular recognition, crystallization, and thermal behavior of the expected binary systems. We found that neat grinding of LID with dicarboxylic acids results in the formation of eutectic phases. The observed eutectic melting points deviated from the ideal eutectic temperatures predicted by the Schroeder van Laar model because of hydrogen bonding between the reacting components within the mixtures. Furthermore, thermal and infrared analysis provided evidence for the possible formation of new phases stemming from partial ionization of the counterions. Besides, the structure of a previously undetermined form I of the tridecanedioic acid was solved by single crystal X-ray diffraction.

Hard polymeric porous microneedles on stretchable substrate for transdermal drug delivery.

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 cm2) 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.

Magnetic Field-Responsive Pulsatile Drug Release Using A Magnetic Fluid.

Ferrofluids are colloidal liquids with fine magnetic particles. They change shape and fluidity depending on the magnitude and direction of the external magnetic field. The magnetic field-responsive pulsatile release of a model drug, lidocaine hydrochloride (LID·HCl), was determined using a depot-type injection containing white petrolatum and/or hydrophilic cream with a magnetic fluid in various proportions. Drug release was confirmed using a self-made diffusion cell and the application of a moving magnet at the bottom of the preparation. Magnetic field-responsive LID release was observed only when using the white petrolatum preparation and depended on the concentration of the magnetic fluid. Magnetic field responsiveness was not observed in the preparation with only the hydrophilic cream. A greater magnetic field-responsive release was observed with a combination of white petrolatum and hydrophilic cream than with white petrolatum alone. These results may lead to the development of an injectable formulation that enables pulsatile administration of macromolecular drugs.

Differences in local anaesthetic and antiepileptic binding in the inactivated state of human sodium channel Nav1.4.

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.

Modification of release and penetration behavior of water-soluble active ingredient from ball-milled glutinous starch matrix via carboxymethylcellulose blending.

This present work describes the possible advantages of carboxymethylcellulose (CMC) blending with ball-milled glutinous starch (BMGS) on the modification of release and penetration of model water-soluble active ingredient, lidocaine hydrochloride, from the blended matrix. The 20-67% CMC mass containing CMC-BMGS matrices were fabricated by casting the aqueous dispersion of CMC-BMGS onto the tray and oven-dried. BMGS and CMC were compatible as revealed by SEM and ATR-FTIR. Irrespective of the CMC mass, all CMC-BMGS matrices showed comparable matrix mass, thickness, moisture content, moisture absorption as well as mechanical and mucoadhesive properties. The surface pH of CMC-BMGS tended to increase with the CMC mass. Depends on CMC mass, matrix properties, release, and penetration rates were modulated significantly. CMC had shown a substantial role in the swelling and erosion behaviors of BMGS films, and thus modulated the release and penetration significantly. The release and penetration mechanisms of active ingredient from the CMC-BMGS matrices were Fickian diffusion-controlled, with rates of release and penetration ranging from 2.05 ± 0.21 to 7.55 ± 1.08%/min½, and from 3.48 ± 0.28 to 8.04 ± 0.64 µg/cm2/min½, respectively. The capability of CMC-BMGS matrices as mucoadhesive delivery systems to provide sustained delivery of water-soluble active ingredients was disclosed.

Metabolomic profiling of single enlarged lysosomes.

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.

Use of Silicone Membrane Permeation to Assess Thermodynamic Activities of Ionic Liquids and Their Component Cation and Anion.

Ionic liquid (IL) was prepared by mixing lidocaine and ibuprofen as a cation and anion, respectively, at various ratios. We determined the permeation of both compounds from the IL through a silicone membrane selected as a model biological membrane, and mathematically analyzed the permeation data from the viewpoint of the thermodynamic activities of lidocaine, ibuprofen, and the IL. As a result, IL and ibuprofen diffusely permeated through the membrane in the case of applying IL preparations with a molar fraction of ibuprofen of 0.5 or higher. The IL was thought to separate into lidocaine and ibuprofen in the receiver. On the other hand, when applying IL preparations with a molar fraction of lidocaine of 0.5 or higher, IL and lidocaine permeated. The permeation rate of IL itself was maximized when the applied IL was prepared using equimolar amounts of lidocaine and ibuprofen, and it decreased when the fraction of lidocaine or ibuprofen increased by more than 0.5. Their membrane permeation rates increased with an increase in their activity, and no more increase was found when the drugs were saturated in the IL. These membrane permeation profiles reflected well the mathematically calculated ones according to the concept of activity.

In situ drug release measuring in α-TCP cement by electrochemical impedance spectroscopy.

The use of drug delivery systems is a good technique to leave the right quantity of medicine in the patient's body in a suitable dose, because the drug application is delivered directly to the affected region. The current techniques such as HPLC and UV-Vis for the drug delivery calculation has some disadvantages, as the accuracy and the loss of the sample after characterization. With the aim of reducing the amount of material used during the characterization and have a non-destructive test with instantaneous results, the present paper shows the possibility of using electrochemical impedance spectroscopy (EIS) to have a drug delivery measurement during the release phenomena for a calcium phosphate cement (CFC) delivery system with gentamicin sulfate (GS) and lidocaine hydrochloride (LH), at a ratio of 1% and 2%, respectively. The equivalent circuit and the chemical mechanism involved during the measurements have been proposed as a tool to determine the drug delivery profile. The method has been compared with the UV-Vis technique. XRD was realized to verify conditions, before and after release. It was possible to verify the potential for using EIS as an instant technique to quantify drug delivery.

Fabrication of Alginate-Based O/W Nanoemulsions for Transdermal Drug Delivery of Lidocaine: Influence of the Oil Phase and Surfactant.

Transdermal drug delivery of lidocaine is a good choice for local anesthetic delivery. Microemulsions have shown great effectiveness for the transdermal transport of lidocaine. Oil-in-water nanoemulsions are particularly suitable for encapsulation of lipophilic molecules because of their ability to form stable and transparent delivery systems with good skin permeation. However, fabrication of nanoemulsions containing lidocaine to provide an extended local anesthetic effect is challenging. Hence, the aim of this study was to address this issue by employing alginate-based o/w nanocarriers using nanoemulsion template that is prepared by combined approaches of ultrasound and phase inversion temperature (PIT). In this study, the influence of system composition such as oil type, oil and surfactant concentration on the particle size, in vitro release and skin permeation of lidocaine nanoemulsions was investigated. Structural characterization of lidocaine nanoemulsions as a function of water dilution was done using DSC. Nanoemulsions with small droplet diameters (d < 150 nm) were obtained as demonstrated by dynamic light scattering (DLS) and cryo-TEM. These nanoemulsions were also able to release 90% of their content within 24-h through PDMS and pig skin and able to the drug release over a 48-h. This extended-release profile is highly favorable in transdermal drug delivery and shows the great potential of this nanoemulsion as delivery system.

Sweet-Tasting Ionic Conjugates of Local Anesthetics and Vasoconstrictors.

Local anesthetics are widely utilized in dentistry, cosmetology, and medicine. Local anesthesia is essential to providing a pain-free experience during dental and local surgeries as well as cosmetic procedures. However, the injection itself may produce discomfort and be a source of aversion. A novel approach toward the taste modulation of local anesthetics is proposed, in which the anesthetics of the "-caine" family serve as cations and are coupled with anionic sweeteners such as saccharinate and acesulfamate. Ionic conjugates of vasoconstrictor epinephrine such as epinephrine saccharinate and epinephrine acesulfamate have also been synthesized. Novel ionic conjugates were developed using anion exchange techniques. Reported compounds are sweet-tasting and are safe to use both topically and as injections.

Lidocaine-loaded reduced graphene oxide hydrogel for prolongation of effects of local anesthesia: In vitro and in vivo analyses.

Lidocaine is widely used as a local anesthetic for alleviation of post-operative pain and for management of acute and chronic painful conditions. Although several approaches are currently used to prolong the duration of action, an effective strategy to achieve neural blockage for several hours remains to be identified. In this study, a lidocaine-loaded Pluronic® F68-reduced graphene oxide hydrogel was developed to achieve sustained release of lidocaine. Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy confirmed the synthesis of Pluronic® F68-reduced graphene oxide. Transmission electron microscopy showed wrinkled, flat nanosheets with micelles attached. The developed hydrogel showed desirable pH, viscosity, adhesiveness, hardness, and cohesiveness for topical application. The ex vivo release study demonstrated the ability of the Pluronic® F68-reduced graphene oxide hydrogel to prolong release up to 10 h, owing to the strong π-π interactions between the graphene oxide and the lidocaine. In comparison with a commercial lidocaine ointment, the developed graphene oxide hydrogel showed sustained anesthetic effect in the radiant heat tail flick test and sciatic nerve block model. Thus, this study demonstrates the potential of using Pluronic® F68-reduced graphene oxide nanocarriers to realize prolonged effects of local anesthesia for effective pain management.

Oleophylic Nanospheres Self-Assembly by Emulsion Technique Utilizing the Automatic Nanoscalar Interfacial Alternation (ANIAE).

BACKGROUND: The administration of many pharmaceutical active ingredients is often performed by the injection of an aqueous-based solution. Numerous active ingredients are however, insoluble in water, which complicates their administration and restricts their efficacy. OBJECTIVE: The current solutions are hindered by both, a time-consuming manufacturing process and unsuitability for hydrophilic and hydrophobic materials. METHODS: Emulsions of oleophilic active ingredients and polyprotein microspheres are an important step to overcome insolubility issues. RESULTS: Polyprotein microspheres offer a versatile modifiable morphology, thermal responsivity, and size variation, which allows for the protection and release of assembled biomaterials. In addition, nanospheres present promising cell phagocytosis outcomes in vivo. CONCLUSION: In this research, a reproducible multifunctional approach, to assemble nanospheres in one step, using a technique termed "automatic nanoscalar interfacial alternation in emulsion" (ANIAE) was developed, incorporating a thermally controlled release mechanism for the assembled target active ingredients. These results demonstrate a viable, universal, multifunctional principal for the pharmaceutical industry.

Immediate Use After Reconstitution of a Biostimulatory Poly-L-Lactic Acid Injectable Implant.

BACKGROUND: Poly-L-lactic acid (PLLA) is a biodegradable, synthetic polymer that stimulates collagen production and can improve skin quality, volume, and thickness. The current reconstitution procedure for Sculptra, a PLLA-containing injectable device involves 2 hours standing time before use. OBJECTIVE: To evaluate and validate an immediate-use procedure for reconstituting a PLLA-containing injectable device. METHODS AND MATERIALS: Three batches of the product were shaken for 1 minute immediately after reconstitution with 8 mL of sterile water. Different physicochemical tests including viscosity, concentration of excipients (sodium carboxymethylcellulose and mannitol), pH, and particle size distribution were performed for standing times 0, 2, 24, and 72 hours after immediate shaking, and compared with the standard 2 hours standing time before shaking. The recovery and stability of optional addition of 1 mL of 2% lidocaine hydrochloride was also assessed. RESULTS: All physiochemical parameters evaluated were equivalent, regardless of reconstitution procedure, showing that shaking vigorously for 1 minute dissolves the excipients of the product properly without a required standing time and with no impact to the PLLA particles. There were no differences in lidocaine hydrochloride content of suspensions after 0 and 72 hours. CONCLUSION: The PLLA-containing product can be used immediately after reconstitution including vigorous shaking, as shown from physicochemical analyses. Optional addition of lidocaine hydrochloride is feasible. J Drugs Dermatol. 2020;19(12): doi:10.36849/JDD.2020.5228.

Evaluation of Physicochemical Properties Following Syringe-to-Syringe Mixing of Hyaluronic Acid Dermal Fillers.

BACKGROUND: Historically, soft-tissue hyaluronic acid (HA) fillers have been mixed with agents to reduce pain or alter physicochemical properties. OBJECTIVE: Evaluate the impact of dilution and mixing on HA filler physicochemical properties. MATERIALS AND METHODS: Crosslinked HA filler (VYC-20L, 20 mg/mL) was diluted to 15 mg/mL using saline through 5 or 10 passes between 2 syringes connected using a luer connector. Extrusion force, rheological properties, and microscopic appearance were assessed. Undiluted VYC-15L (15 mg/mL) served as the control. RESULTS: Average extrusion force was higher for diluted VYC-20L versus the control, with an increase in slope for gel diluted using 5 passes (0.65) and 10 passes (0.52) versus the control (<0.1). For diluted samples mixed with 5 or 10 passes, the rheological profile was different between the 2 halves of the syringe, with the second half more elastic than the first half, compared with the consistent profile of undiluted samples. Microscopically, diluted VYC-20L samples seemed more liquid near the luer and more particulate near the piston compared with the control, which was smooth throughout. CONCLUSION: In addition to potentially introducing contamination, diluting or mixing soft-tissue HA fillers yields a heterogeneous product with physicochemical characteristics that vary substantially throughout the syringe.