Concurrent Determination of Pridinol, Diclofenac and Impurity A by HPLC-UV

A reversed-phase high-performance liquid chromatography method was developed and validated for the simultaneous determination of pridinol, diclofenac and diclofenac-related compounds in tablet formulations. The proposed method is also suitable for content uniformity determination, for dissolution test and for stability studies. Separation was achieved on a base-deactivated silica C8 column, using 50 mM phosphate buffer (pH 2.5) and methanol (40:60 v/v) as mobile phase, at a flow rate of 1.0 mL/min and column temperature of 40°C. Ultraviolet detection was made at 225 nm. The method was validated for specificity, accuracy, precision (intraday and interday levels) and linearity for each analyte. For diclofenac impurity A, sensitivity was also studied. The method showed specificity and linearity (R2: 0.999 for the three analytes) over the assessed concentration range (diclofenac: 2.5-75.0 μg/mL, pridinol: 2.0-60.0 μg/mL and impurity A: 1.25-5.0 μg/mL) and demonstrated good precision as reflected by the low coefficient of variation in all cases. Recovery rates obtained were 99.81, 100.58 and 100.96% for diclofenac, pridinol and impurity A respectively, and for all three analytes, the variances of the concentrations tested were equivalent. The detection and quantitation limits for impurity A were 0.078 and 0.261 μg/mL, respectively.

Portable capillary electrophoresis coupled with swab-based extraction device for cleaning validation in pharmaceutical facilities

All pharmaceutical manufacturers are required to verify that their production equipment is free from contaminants. Here, we report the capability of a fully automated portable capillary electrophoresis instrument with an integrated sample swab extraction - the Grey Scan ETD-100 - for the detection of pharmaceutical residues on surfaces of manufacturing equipment. Lidocaine was used as a model compound and could be recovered from a surface by swabbing, extracted from the swab, and analysed within 1 min. The recovery of lidocaine from a stainless-steel coupon was 81.3 %, with a LOD of 0.13 µg/swab. This fast, sensitive, and simple method implemented on a user-friendly portable CE instrument without the need for manual sample pre-treatment provides the possibility for on-site rapid determination of equipment cleanliness in the pharmaceutical industry.

TLC–Densitometry for Determination of Omeprazole in Simple and Combined Pharmaceutical Preparations

TLC combined with densitometry was used and chromatographic conditions developed to separate omeprazole and diclofenac sodium from their potential impurities. The development of the TLC–densitometry method is based on the elaboration of new chromatographic conditions allowing for the simultaneous determination of omeprazole and diclofenac sodium in a pharmaceutical preparation. Identification and quantification of omeprazole in simple and combined (with diclofenac) pharmaceutical preparations was performed on silica gel 60F₂₅₄ using one mobile phase: chloroform–methanol–ammonia (36:4:0.60, v/v). Diclofenac sodium was determined in the presence of omeprazole after 2D separation on silica gel using two mobile phases of the first phase of chloroform–methanol–ammonia (36:4:0.60, v/v) and the second mobile phase cyclohexane–chloroform–methanol–glacial acetic acid (6:3:0.5:0.5 v/v). The developed method is simple, economical, specific, precise, accurate, sensitive, and robust, with a good range of linearity for the quantification of omeprazole and diclofenac sodium. TLC in combination with densitometry can be used as an effective analytical tool for quality control and quantitative determination of omeprazole in simple and combined pharmaceutical preparations containing diclofenac sodium. TLC in combination with densitometry can be recommended for the analysis of omeprazole and diclofenac sodium in the absence of HPLC or spectrophotometer in the laboratory or to confirm results obtained with other analytical techniques.

Evaluation of Lidocaine and Metabolite Pharmacokinetics in Hyaluronic Acid Injection

Lidocaine-incorporated hyaluronic acid injection (LHA) is considered a promising way to increase patient compliance. Various reviews and analyses have been conducted to verify that the addition of lidocaine had no effect on the product quality of hyaluronic acid injections. However, possible pharmacokinetic (PK) alterations of lidocaine and its active metabolites, monoethylglycylxylidide (MEGX) and glycylxylidide (GX), in hyaluronic acid injection have not been studied so far. Thus, the objective of this study was to evaluate lidocaine and its metabolite PK after 0.3% lidocaine solution or LHA injection and to investigate any changes in PK profiles of lidocaine and its active metabolites. To do this, a novel bio-analytical method for simultaneous determination of lidocaine, MEGX, and GX in rat plasma was developed and validated. Then, plasma concentrations of lidocaine and its active metabolites MEGX and GX following subcutaneous (SC) injection of 0.3% lidocaine solution or LHA with 0.3–1% lidocaine in male Sprague-Dawley rats were successfully determined. The obtained data were used to develop a parent-metabolite pharmacokinetic (PK) model for LHA injection. The half-life, dose-normalized C_max, and AUC_inf of lidocaine after SC injection of lidocaine solution and LHA did not show statistically significant difference. The PK characteristics of lidocaine after LHA administration were best captured using a two-compartment model with combined first-order and transit absorption and its clearance described with Michaelis–Menten and first-order elimination kinetics. Two one-compartment models were consecutively added to the parent model for the metabolites. In conclusion, the incorporation of lidocaine in hyaluronic acid filler injection did not alter the chemical’s pharmacokinetic characteristics.

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.

Simultaneous quantification of lidocaine and prilocaine in human plasma by LC-MS/MS and its application in a human pharmacokinetic study

OBJECTIVE

The aim of the work was to develop and validate a simple, sensitive and selective Liquid chromatography with Mass spectroscopic method for simultaneous quantification of lidocaine and prilocaine in human plasma.

DESIGN AND METHODS

Analytes and the internal standards from human plasma were extracted by using solid- phase extraction technique using Waters Oasis® HLB 1 ​cc (30 ​mg) cartridges. The reconstituted samples were chromatographed on Phenomenex Kinetex EVO 4.6*100 ​mm 2.6 μ 100A column by using a mixture of acetonitrile and 5 ​mM ammonium acetate buffer (80:20, v/v) as the mobile phase at a flow rate of 0.6 ​mL/min.

RESULTS

The method was validated over the concentration range of 0.10-201.80 ng/mL for lidocaine and 0.10-201.66 ng/mL for prilocaine. The calibration curve obtained was linear.

CONCLUSION

Method validation was performed as per FDA guidelines and the results met the acceptance criteria. A run time of 3.0 min for each sample, make it possible to analyze more than 350 human plasma samples per day. The proposed method was found applicable for pharmacokinetic studies.

A comprehensive strategy in the development of a cyclodextrin-modified microemulsion electrokinetic chromatographic method for the assay of diclofenac and its impurities: Mixture-process variable experiments and quality by design

A comprehensive strategy involving the use of mixture-process variable (MPV) approach and Quality by Design principles has been applied in the development of a capillary electrophoresis method for the simultaneous determination of the anti-inflammatory drug diclofenac and its five related substances. The selected operative mode consisted in microemulsion electrokinetic chromatography with the addition of methyl-β-cyclodextrin. The critical process parameters included both the mixture components (MCs) of the microemulsion and the process variables (PVs). The MPV approach allowed the simultaneous investigation of the effects of MCs and PVs on the critical resolution between diclofenac and its 2-deschloro-2-bromo analogue and on analysis time. MPV experiments were used both in the screening phase and in the Response Surface Methodology, making it possible to draw MCs and PVs contour plots and to find important interactions between MCs and PVs. Robustness testing was carried out by MPV experiments and validation was performed following International Conference on Harmonisation guidelines. The method was applied to a real sample of diclofenac gastro-resistant tablets.