A simple and high-resolution HPLC-PDA method for simultaneous quantification of local anesthetics inin vitrobuccal permeation enhancement studies

A Green-and-White Integrative Analytical Strategy Combining Univariate and Chemometric Techniques for Quantifying Recently Approved Multi-Drug Eye Solution and Potentially Cancer-Causing Impurities: Application to the Aqueous Humor

BACKGROUND

Drug impurities are now seen as a major threat to the production of pharmaceuticals around the world and a major part of the global contamination problem, especially when it comes to carcinogenic impurities.

OBJECTIVE

We present the first spectrophotometric strategy based on a combination of univariate and multivariate methods as impurity profiling methods for the estimation of lignocaine (LIG) and fluorescein (FLS) with their carcinogenic impurities: 2,6-xylidine (XYL) and benzene-1,3-diol (BZD).

METHOD

The data processing strategy depends on overcoming unresolved bands by employing five affordable, accurate, selective, and sensitive methods. The methods applied were a direct UV univariate spectrophotometric analysis (D0) and four multivariate chemometric methods, including classical least squares (CLS), principal component regression (PCR), partial least squares (PLS), and genetic algorithm (GA-PLS). FLS analysis (1-16 μg/mL) was performed using the D0 method at 478 nm; then, the application of the ratio subtraction method (RSM) allowed the removal of interference caused by the FLS spectrum. From the resulting ratio spectra, LIG, XYL, and BZD can be efficiently determined by chemometrics. The calibration set was carefully selected at five concentration levels using a partial factorial training design, resulting in 25 mixtures with central levels of 160, 40, and 3 μg/mL for LIG, XYL, and BZD, respectively. Another 13 samples were applied to validate the predictive ability.

RESULTS

The statistical parameters demonstrated exceptional recoveries and smaller prediction errors, confirming the experimental model's predictive power.

CONCLUSIONS

The proposed approach was effectively tested using newly FDA-approved LIG and FLS pharmaceutical preparation and aqueous humor. Additionally, it was effectively assessed for whiteness, greenness, and sustainability using five assessment tools.

HIGHLIGHTS

With its remarkable analytical performance, sustainability, affordability, simplicity, and cost-efficiency, the proposed strategy is an indispensable tool for quality control and in situ analysis in little-equipped laboratories, increasing the proposed approach's surveillance ability.

A membrane-protected microsolid phase-extraction method based on molecular imprinting and its application to the determination of local anesthetics in cosmetics

As local anesthetics (LAs) that are illegally added into cosmetics are harmful to consumer health, it is necessary to establish an efficient method for detecting these substances. Herein, a molecularly imprinted polymer (bupivacaine) was prepared by bulk polymerization and packed into a hollow fiber for use as an extraction phase to fabricate a membrane-protected microsolid phase-extraction device. The optimal values of the influencing parameters for the microextraction process were as follows: a sample solution pH of 9.0, a loading and washing time of 2 h and an elution time of 32 min. A GC-MS method was established for determination of local anesthetics and coupled with the microextraction method to successfully detect local anesthetics in cosmetic samples. The calibration curve for the proposed method was linear in the range of 0.4∼50 mg/L and showed a good correlation coefficient (r² ). The LODs for local anesthetics were in the range of 0.01∼0.71 mg/L. The molecularly imprinted polymer exhibited good imprinting and selectivity, and the microsolid phase-extraction device was simple and inexpensive and fabrication was reproducible. The combination of molecular imprinting technology, membrane separation and microsolid phase-extraction methods used in this study can potentially be applied to pretreat local anesthetics in cosmetic samples. This article is protected by copyright. All rights reserved.

Needle-free anesthesia: clinical efficacy of a mucoadhesive patch for atraumatic anesthesia in dental procedures

This study showcases the clinical efficacy of mucoadhesive patches designed for the buccal delivery of lidocaine and prilocaine hydrochlorides (1:1, 30 mg/patch). Such patches were developed for needle-free pre-operative local anesthesia in dentistry, aiming at mitigating the use of infiltrative anesthesia for medium-complexity clinical procedures. The patches were manufactured encompassing drug-release, mucoadhesive and backing layers, all prepared through film casting using biocompatible materials. Fifty-eight (n = 58) adult patients (65% women and 35% men) were randomly selected and included in a one-arm open clinical prospective cohort study. The average age of the subjects was of 50 years. The majority (59%) of the subjects, mostly women (82%), reported needle-phobia or anxiety due to dental procedures, which was assessed through a questionnaire approved by the ethical council for human use in research. The patches were positioned in the gingival region of the teeth involved in the procedure (86% on the maxillary and 14% on the mandibular bone). Two anesthetic patches were applied on each patient: one in the vestibular region and another in the palate/lingual portion, and these patches remained attached to the placement sites throughout the procedures. Concerning the dental procedures performed, 40% were cavity preparations and dental restorations of medium cavities; 29% staple facilities; 10% gingival retractions; 9% subgingival scrapings; 3% gingivalplasties; 3% supragingival preparations; 3% occlusal adjustments; and 2% subgingival preparations. In 90% of the cases, it was not necessary to complement with conventional infiltrative local anesthesia during the procedures. Patients did not report any discomfort or side effect during or after the administration of the patches. Among the cases in which there was the need for complementation, 50% were cavity preparations and dental restorations; 33% supragingival preparations; and 17% gingivoplasties. The complementary anesthesia volume was of 0.63 ± 0.23 mL and women corresponded to 83% of the participants who needed such intervention. Furthermore, in most cases, the patch was capable of initiating the anesthesia within a short time frame (5 minutes) and reaching the maximum anesthetic effect within 15 and 25 min, lasting at least 50 min. Undesirable side effects were not reported either 2 h after the administration or within the 6-month follow-up. Therefore, the anesthetic patches developed provide needle-free, painless, safe, and patient/dentist-friendly advances in performing routine medium-complexity dental procedures.

Herpes Labialis: A New Possibility for Topical Treatment with Well-Elucidated Drugs

Mucocutaneous infections caused by Herpes simplex virus (HSV-1 and HSV-2) are characterized by the appearance of vesicles that cause pain and embarrassment to the carrier. The standard treatment is based on the use of antivirals in gels or ointments, however, relapses are common. Local anesthetics decrease the pain caused by the lesion, in addition to showing antiviral properties. Semi-solid form facilitates application and its transformation into a thin film favors the maintenance of the formulation in place, with a more discreet final aspect. The objective of this study was to develop and evaluate formulations containing anesthetics for the treatment of cold sores. For this purpose, two semi-solid film-forming formulations were developed and evaluated, containing HPMC K100, lidocaine (LIDO) and prilocaine (PRILO) combined with adjuvants, in the presence (F1T) or not (F1) of the absorption promoter Transcutol®. The mixture of PRILO and LIDO resulted in the formation of a eutectic mixture (EM), essential for penetration of drugs into the skin. The quantification of drugs was performed by HPLC (High Performance Liquid Chromatography), and Transcutol® did not influence the release of drugs from the formulation. The bioadhesiveness of the formulation was evaluate and the drugs did not impair the adhesive potential of the polymers used. The formulations were evaluated in vivo for skin irritation and did not show any negative sign on macroscopic examination. The in vivo efficacy test proved the anesthetics' ability to decrease the lesions caused by HSV-1. Thus, the proposed formulations proved to be good alternatives to the treatment of oral lesions caused by HSV-1.

Lipid nanocapsules loaded with prilocaine and lidocaine and incorporated in gel for topical application

Lipid nanocapsules (LNC) are special drug delivery system (DDS) carriers obtained by the phase-inversion temperature method (PIT). This study describes the encapsulation of the local anesthetics (LA) prilocaine (PLC) and lidocaine (LDC) in lipid nanocapsules (LNC_PLC+LDC) optimized by 2³ factorial design, characterized through DLS, NTA, CRYO-EM and release kinetics and incorporated in carbopol gel (Gel_{LNC PLC+LDC}) prior to in vivo anesthetic effect (in mice) evaluation. A very homogeneous population of small (50 nm; polydispersity index = 0.05) spherical nanocapsules with negative zeta potentials (-21 mV) and ca. 2.3 × 10¹⁵ particles/mL was obtained. The encapsulation efficiency was high (81% and 89% for prilocaine and lidocaine, respectively). The release rate profile was free PLC = free LDC > LNC_PLC+LDC > Gel_{LNC PLC+LDC}. The hybrid system increased (4x) the anesthesia time in comparison to an equipotent gel formulation prepared without LNC. No tissue damage was detected on the tail skin of mice that received the formulations. This study shows that lipid nanocapsules are suitable carriers for PLC and LDC, promoting longer and safer topical anesthesia. Gel_{LNC PLC+LDC} is mucoadhesive and suitable for application in the mouth, where it could be used as a pre-anesthetic, to reduce pain of needle stick (infiltrative anesthesia).

Innovative Mucoadhesive Precursor of Liquid Crystalline System Loading Anti-Gellatinolytic Peptide for Topical Treatment of Oral Cancer

Current researches report an actual benefit of a treatment for oral cancer via inhibition of proteolytic matrix metallopro-teinases (MPP) with a peptide drug, called CTT1. However, peptides present poor oral bioavailability. Topical administration on oral mucosa avoids its passage through the gastrointestinal tract and the first-pass liver metabolism, but the barrier function of the oral mucosa can impair the permeation and retention of CTT1. The objective of this study is to incorporate CTT1 into a mucoadhesive precursor of liquid crystalline system (PLCS) as an interesting strategy for the topical treatment of oral cancer. PLCS consisting of oleic acid, ethoxylated 20 and propoxylated cetyl alcohol 5, polyethyleneimine (P)-associated chitosan (C) dispersion and CTT1 (FPC-CTT1) was developed and characterized by polarized light microscopy (PLM) and small-angle X-ray scattering (SAXS). In vitro permeation and retention across esophageal mucosa, In vitro cytotoxicity towards tongue squamous cell carcinoma cells, and in vivo evaluation of vascular changes using the chick embryo chorioallantoic membrane (CAM) model were performed. PLM and SAXS showed that FPC-CTT1acted as PLCS, because it formed a lamellar liquid crystalline system after the addition of artificial saliva. FPC-CTT1increased approximately 2-fold the flux of permeation and 3-fold the retention of CTT1 on the porcine esophageal mucosa. CTT1 does not affect cell viability. CAM tests showed that FPC preserved the blood vessels and it can be a safe formulation. These findings encourage the use of the FPC-CTT1 for topical treatment of oral cancer.

Towards the advance of a novel iontophoretic patch for needle-free buccal anesthesia

The aim of this work was to develop a mucoadhesive iontophoretic patch for anesthetic delivery in the buccal epithelium. The patch was comprised of three different layers, namely i) drug release (0.64 cm²); ii) mucoadhesive (1.13 cm²); and iii) backing (1.13 cm²). Prilocaine and lidocaine hydrochlorides were used as model drugs (1:1 ratio, 12.5 mg per unit). An anode electrode (0.5 cm² spiral silver wire) was placed in between the drug release and mucoadhesive/backing layers to enable iontophoresis. Surface microscopy; mechanical and in vitro mucoadhesive properties; drug release kinetics and mechanism; and drug permeation through the porcine esophageal epithelium were assessed. Topographic analysis evidenced differences in the physical structures for the several layers. All layers presented suitable handling properties i.e., flexibility, elasticity and resistance. Both the release and mucoadhesive layers presented features of a soft and tough material, while the backing layer matched the characteristics of a hard and brittle material. A synergy between the drug release and mucoadhesive layers on the mucoadhesive force and work of adhesion of the tri-layered patch was observed. Passive drug release of both drugs fitted to First-order, Hixson-Crowell and Weibull kinetic models; and the release mechanism was attributed to anomalous transport. Iontophoresis remarkably enhanced the permeation of both drugs, but mainly prilocaine through the mucosa as evidenced by the permeability coefficient parameter (3.0-fold). The amount of these amino amide salts retained in the mucosa were also equally enhanced (4.7-fold), while the application of a tiny constant electric current (1 mA·cm^-2·h^-1) significantly decreased the lag time for lidocaine permeation by about 45%. In view of possible in vitro / in vivo correlations, the buccal iontophoretic patch displays a promising strategy for needle-free and patient-friendly local anesthesia in dentistry.

Green spectrophotometric methods for the determination of a binary mixture of lidocaine hydrochloride and cetylpyridinium chloride in the presence of dimethylaniline

Three green, simple, precise, accurate and sensitive spectrophotometric methods were developed for the determination of a binary mixture of lidocaine hydrochloride (LDC) and cetylpyridinium chloride (CPC) in the presence of dimethylaniline (DMA). In the three methods, the interference of DMA spectrum is eliminated using the ratio subtraction method. Method (A) depended on determining LDC and CPC by measuring the first derivative of the ratio spectra (¹DD) at 271.0 and 268.4 nm, respectively. Method (B) was the ratio difference (RD), based on dividing the absorption spectrum of the binary mixture by a standard spectrum of CPC or LDC, then measuring the amplitude difference of the ratio spectra (∆P) between 231.2 and 240.0 nm for LDC and between 242.8 and 258.0 nm for CPC. Method (C) based on the application of dual wavelength coupled with the isoabsorptive point method. This was achieved by measuring the absorbance difference (∆A) between 243.0 and 268.6 nm for the determination of LDC, followed by application of isoabsorptive point method comprised of measurement the total content of the mixture of LDC and CPC at their isoabsorptive point at 240.0 nm. The content of CPC was obtained by subtraction. The specificity of the developed methods was investigated by analyzing laboratory prepared mixtures containing different ratios of LDC and CPC in presence of DMA. The proposed methods displayed useful analytical characteristics for the determination of LDC and CPC in bulk powder and their combined dosage form. The obtained results were statistically compared with those obtained by the official methods, showing no significant difference with respect to accuracy and precision.

A New Approach to Ex Vivo Permeation Studies in In-Situ Film-Forming Systems

The skin is the largest human organ and an important topical route. Even with some challenges, it is an important ally in medication administration, mainly because it is painless and easy-to-apply. Semisolid formulations are the most used dosage forms for drug administration via this delivery route and can be optimized when transformed into a film, favoring on-site maintenance, and promoting drug permeation. However, in situ film-forming systems are difficult to assess and characterize using Franz-type diffusion cells once this apparatus is ideal to formulations without transition phases. The present study proposed a different method to characterize these formulations and provide complementary data on drug and penetration enhancer behaviors, as close as possible to real application conditions. This characterization method allowed us to analyze drug concentration on three necessary occasions: remaining in the polymer film, stratum corneum using adhesive tape, and skin to check where drugs will have a desirable effect. As a proof-of-concept, the proposed ex vivo permeation method was used to evaluate a film-forming system containing lidocaine and prilocaine. We could also evaluate transition phases of drug compositions and quantify drugs at key times after application. Hence, the developed method may be used to provide complementary data to the Franz diffusion cell method, in terms of drug and penetration enhancer behaviors incorporated into film-forming delivery systems.