Current Pharmaceutical Analysis - Volume 15, Issue 3, 2019

Background: Electrochemical techniques can easily be adopted to solve many problems of pharmaceutical interest. The implementation of electroanalytical methods in the assay of pharmaceutical formulations has increased greatly. Nowadays, owing to the critical importance of electron transfer and surface properties, chemically modified electrodes have been employed in electrochemical sensors. The chemically modified electrode is one of the most popular electroanalytical sensors and used in several applications. Methods: In this work, a β-cyclodextrine/multi-walled carbon nanotubes (β-CD/MWCNTs) composite modified glassy carbon electrode (GCE) was produced and applied to the detection of Rivastigmine hydrogen tartrate (RVT) in pharmaceutical formulations. The voltammetric feature of RVT at this β- CD/MWCNTs modified electrode was evaluated using cyclic voltammetry and square wave voltammetry. Results: The β-cyclodextrin and multi-walled carbon nanotubes modified glassy carbon electrode displayed good electrocatalytic activity in the oxidation of rivastigmine hydrogen tartrate with relatively high sensitivity, stability and lifetime. The calibration graph of the analyte was linear over the range 10- 1500 μM with two linear segments and the detection limit was obtained as 2.0 μM (S/N=3). The results showed that the electrochemical sensor has good sensitivity and selectivity. Conclusion: The β-CD/MWCNTs modified electrode displayed a high electrochemical activity and good sensitivity toward the oxidation of RVT. Compared with the bare MWCNTs coated sensor, the response of analyte increased soundly and the response potential of target analyte shifted negatively. The results indicated that the β-CD/MWCNTs film coated electrode had good catalysis to the voltammetric oxidation of RVT. The prepared sensor was applied to determine RVT in pharmaceutical samples with satisfactory yields. The outcomes indicate that β-CD/MWCNTs coated electrode is a safe choice for the detection of RVT.

Background: Drug stability is essential in the process of drug production, storage, appliance, and so on. Some drugs' degradation products may even have a toxic side effect, which can result in safety risks and economic losses. Therefore, it is very imperative to develop a suitable stability indicating an analytical method for anastrozole which could be used for stability testing, routine and in-process quality control analysis or other further studies. Methods: A reverse-phase high-performance liquid chromatography method was developed and validated for the degradation kinetics study of anastrozole, a selective non-steroid third-generation aromatase inhibitor, which would provide a basis for further studies on anastrozole. The degradation product was confirmed by ultra-performance liquid chromatography with tandem mass spectrometry. Results: Results showed that the degradation behavior of anastrozole followed first-order kinetics in different temperatures, pH values and oxidation conditions. It was suggested that the degradation behavior of anastrozole was pH-dependent and it's more stable at lower pH values. Conclusion: A high performance liquid chromatography method was established and used to determine the residual concentration of anastrozole in this study. It was found that the degradation behavior of anastrozole followed first-order kinetics at different temperatures, pH values and oxidation conditions. According to the results, the degradation of anastrozole was found to be pH-dependent and it is more unstable in alkaline conditions. The information of degradation kinetics will be useful for understanding the chemical stability of anastrozole and provide a reference for the further preparation research and clinical therapy of anastrozole.

Introduction: Artificial enzyme mimics are materials with similar catalytic function of natural enzymes. Among several types of artificial enzymes, nanomaterial-based products or nanozymes have been of particular interest to researchers. Materials and Methods: In this work, Ce2(MoO4)3 nanoplates were synthesized via a one-pot hydrothermal approach. SEM and EDS characterizations show a plated-like architecture with high purity. These nanoplates are shown to have an intrinsic peroxidase-mimetic activity. In the presence of H2O2, Ce2(MoO4)3 nanoplates could catalyse the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with high performance to produce a blue dye (with an absorbance maximum at 652 nm). Dopamine (DA) has some reducibility due to the phenol hydroxyl group, which results in using H2O2 and causing the blue shallowing of the reaction solution by inhibiting the reaction between H2O2 and TMB. Based on that, a visual, sensitive and simple colorimetric method using Ce2(MoO4)3 nanoplates as peroxidase mimics was developed for detecting DA. Results and Conclusions: Suitable linear relationship for DA was obtained from 0.1 to 10 μM. The limit of detection (LOD) of the proposed method was calculated as 0.05 μM and the relative standard deviation (RSD) was less than 4.0%. The proposed method was successfully applied to DA detection in human serum sample.

Background: It is urgently needed to clarify the pharmacokinetic mechanism for the multibioactive constituents in Traditional Chinese Medicines for its clinical applications. A rapid, sensitive and reliable ultra-performance liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous determination of Danshensu, Ferulic acid, Astragaloside IV, Naringin, Neohesperidin and Puerarin after oral administration of Naoshuantong Granule using Carbamazepine as internal standard (IS). Methods: The plasma samples were pretreated by liquid-liquid extraction method using ethyl acetate after acidification, and separated on a Waters ACQUITY UPLC® BEH C18 column (50.1 mm, i.d., 1.7 μm) by gradient elution with a mobile phase composing of water (containing 0.1% formic acid) and acetonitrile at a flow rate of 0.2 mL/min. Multiple reaction monitoring (MRM) mode with both positive and negative ion mode was operated using an electrospray ionization (ESI) to detect the six compounds. Result: All calibration curves showed good linearity (r>0.99) over a wide concentration range. The intra- and inter-day precision (RSD%) was below 8.4% and the accuracy (RE%) ranged from 91.1% to 107.5%. The extraction recoveries of the six analytes and IS in the plasma were more than 77.9% and no severe matrix effect was observed. Conclusion: The fully validated method was successfully applied to the pharmacokinetics of Naoshuantong Granule.

Introduction: Trimetazidine and Metoprolol combination is more effective in the treatment of cardiac disorders as compared to single drug therapy. Materials and Methods: A rapid, simple, and sensitive HPTLC method was developed for the simultaneous determination of Trimetazidine and metoprolol from its tablet dosage form and validated. In HPTLC method, standard and sample solutions of Trimetazidine hydrochloride and metoprolol succinate were applied on pre-coated silica gel G 60 F254 TLC plate, and developed by using mobile phase, n-butanol :water: methanol: ammonia as solvent (8.5:0.1:0.1: 0.85, v/v). The drugs on plate were scanned at 213 nm. The method produced compact and well-resolved bands at Rf of 0.32 ± 0.02 and 0.66 ± 0.02 for Trimetazidine Hydrochloride and Metoprolol succinate respectively. The range for linearity was observed as 500-2500 ng band-1 for Trimetazidine hydrochloride and 500-2500 ng band-1 for metoprolol succinate and correlation coefficient were 0.9991 and 0.9997 respectively. Conclusion: The developed method was validated according to the ICH guidelines for precision, accuracy, Limit of detection, Limit of quantitation, specificity and robustness. The method was checked for suitability in determination of Trimetazidine hydrochloride and Metoprolol succinate in their tablet dosage form. The assay result was found to be 99.64 % ± 0.45 and 99.94 % ± 0.53 of percentage label claim for Trimetazidine hydrochloride and Metoprolol succinate respectively.

Background: Molecularly imprinted polymers (MIPs) are synthetic polymers that have a selective site for a given analyte, or a group of structurally related compounds, that make them ideal polymers to be used in separation processes. Objective: An optimized molecularly imprinted polymer was selected and applied for selective extraction and analysis of clozapine in rat brain tissue. Methods: A molecularly imprinted solid-phase extraction (MISPE) method was developed for preconcentration and cleanup of clozapine in rat brain samples before HPLC-UV analysis. The extraction and analytical process was calibrated in the range of 0.025-100 ppm. Clozapine recovery in this MISPE process was calculated between 99.40 and 102.96%. The limit of detection (LOD) and the limit of quantification (LOQ) of the assay were 0.003 and 0.025 ppm, respectively. Intra-day precision values for clozapine concentrations of 0.125 and 0.025 ppm were 5.30 and 3.55%, whereas inter-day precision values of these concentrations were 9.23 and 6.15%, respectively. In this study, the effect of lipid emulsion infusion in reducing the brain concentration of drug was also evaluated. Results: The data indicated that calibrated method was successfully applied for the analysis of clozapine in the real rat brain samples after administration of a toxic dose to animal. Finally, the efficacy of lipid emulsion therapy in reducing the brain tissue concentration of clozapine after toxic administration of drug was determined. Conclusion: The proposed MISPE method could be applied in the extraction and preconcentration before HPLC-UV analysis of clozapine in rat brain tissue.

Background: A robust and validated analytical method is a key component at various stages of pharmaceutical product development to ensure identity, purity and quality of drugs and formulations. Objective: The aim of proposed work was to develop and validate a simple, sensitive and stability indicating high performance liquid chromatographic method for the estimation of venlafaxine hydrochloride in bulk and formulations for routine analysis as well as for preformulation studies. Methods: Efficient chromatographic separation has been performed on a HpyercloneTM 5μm BDS C18 column using a mobile phase consisting of a mixture of phosphate buffer (25 mM, pH 3.0) and acetonitrile (70:30 v/v) at a flow rate of 1 ml min-1. Venlafaxine hydrochloride was analyzed using UV detector at 225nm. Developed method was validated as per ICH guidelines. Results: The method has demonstrated linearity over the range of 100 to 2000 ng ml-1 with regression equation, mean peak area (y) = 93.32 x concentration - 322.00 (R2 = 1). The method has demonstrated good and consistent recovery (99.34 to 101.16%). Precision of the method reflected by the relative standard deviation values at intra-day and inter-day levels was less than 1.79%. The detection and quantitation limits were 6.55 ng ml-1 and 19.84 ng ml-1 respectively indicating sensitivity of the method. The method was successfully applied for the estimation of venlafaxine hydrochloride in marketed and inhouse formulations. Also, developed method was successfully used in drug-excipients compatibility studies for VEN. Conclusion: The method was found to be accurate, precise, sensitive and selective for the determination venlafaxine hydrochloride in bulk and pharmaceutical formulations.

Background: Salvianolic acid A (SAA) is a polyphenolic acid extracted from Salvia miltiorrhiza Bunge. It showed protective effect against diabetic complications after oral administration with a low bioavailability of 1.42%. Attempts have been made to develop it into a new medication. Intracorporal process of SAA is indistinct and no report regarding the excretion is available. Our preliminary experiment revealed that previous reported methods were unsuitable for the excretion study due to the serious matrix effect. Methods: To better clarify its pharmacokinetics and avoid the interference of complex endogenous substances, a sensitive UPLC-MS/MS method with a better resolution was developed for the excretion study of SAA for the first time. The analytes were separated by reversed-phase chromatography with acetonitrile-water (containing 0.1% formic acid) gradient elution. The mass spectrometer was operated in the negative ESI mode and multiple reaction monitoring mode. Results: This method was linear over the concentration range of 2.5-100, 5-100 and 5-100 ng/mL in urine, feces and bile, respectively. The accuracy, precision, stability, recovery and matrix effect were satisfactory in all matrices examined. The validated method was successfully applied to an excretion study in rats. After oral administration of 20 mg/kg, the average accumulated excretion amount of SAA in urine, feces and bile were 99.80, 32046.30 and 161.03 ng, respectively. Conclusion: A quick but low elimination was observed. The date is useful for the clinical trial design of SAA.

Background: The unstable and/or toxic degradation products may form due to degradation of drug which results into loss of therapeutic activity and lead to life threatening condition. Hence, it is important to establish the stability characteristics of drug in various conditions such as in temperature, light, oxidising agent and susceptibility across a wide range of pH values. Introduction: The aim of the proposed study was to develop simple, sensitive and economic stability indicating high performance thin layer chromatography (HPTLC) method for the quantification of Amoxapine in the presence of degradation products. Methods: Amoxapine and its degraded products were separated on precoated silica gel 60F254 TLC plates by using mobile phase comprising of methanol: toluene: ammonium acetate (6:3:1, v/v/v). The densitometric evaluation was carried out at 320 nm in reflectance/absorbance mode. The degradation products obtained as per ICH guidelines under acidic, basic and oxidative conditions have different Rf values 0.12, 0.26 and 0.6 indicating good resolution from each other and pure drug with Rf: 0.47. Amoxapine was found to be stable under neutral, thermal and photo conditions. Results: The method was validated as per ICH Q2 (R1) guidelines in terms of accuracy, precision, ruggedness, robustness and linearity. A good linear relationship between concentration and response (peak area and peak height) over the range of 80 ng/spot to 720 ng/spot was observed from regression analysis data showing correlation coefficient 0.991 and 0.994 for area and height, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) for area were found to be 1.176 ng/mL and 3.565 ng/mL, whereas for height, 50.063 ng/mL and 151.707 ng/mL respectively. Conclusion: The statistical analysis confirmed the accuracy, precision and selectivity of the proposed method which can be effectively used for the analysis of amoxapine in the presence of degradation products.

Background: The presence of impurities in vancomycin compromised the safety and contributed to decrease of its use for years. In Brazil, vancomycin generic drug represents an option to reduce hospital costs. However, the controversy over the quality of these formulations and their relationship to effectiveness and safety raised concerns. Objective and Methods: To assess in vitro quality of vancomycin injections through uniformity of weight, pH, clarity of solution, microbiological assay and impurities determination by High Performance Liquid Chromatography (HPLC). Results: The samples were approved in the tests. Conclusion: The injectable formulations of vancomycin proved to be safe for use in hospital environment. This work contributes to increase health professionals’ confidence on generic vancomycin.

Background: Alpiniae Oxyphyllae Fructus (Yizhi in Chinese) have been widely used as an herbal medicine for the treatment of diuresis, enuresis and diarrhea in China. Many studies have deciphered some potential underlying mechanisms for its anti-diarrheal effects. However, tissue distribution of Yizhi constituents is warranted because pharmacological receptors are frequently located in tissues. Moreover, it is also interesting to know about the potential correlation between behavior in drug distribution and the observed pharmacological response. The aim of this study is to investigate tissue distribution behaviors of Yizhi constituents after oral administration of Yizhi extract to rats, focusing on 10 active principles. Methods: Twenty four male Sprague Dawley rats were given orally the Yizhi extract and fourteen tissue samples were collected after being killed by bleeding from the abdominal aorta under ether anesthesia at different time-points. The resulting tissues were excised and homogenized. Based on our previous reports, liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to quantify the target analytes, as well as phase II metabolites, in the various biosamples. Results: Almost all the targeted Yizhi active principles and some glucuronidated metabolites were qualitatively measured in rat stomach, small intestine, large intestine, as well as liver. Nootkatone, yakuchinone A and tectochrysin were observed in the rat brain. In other rat tissues, these analytes had lower exposure or could not be detected. Consistently, quantitative analysis revealed that the Yizhi active principles dominantly distributed into gastrointestinal tissues followed by liver, the overall exposure levels ranking as follows: stomach > small intestine > large intestine > liver. Tissue concentrationtime profiles of the test active principles in rat stomach, small intestine, and large intestine were bimodal with two concentration peaks occurring at 0.5 and 4h after oral administration, respectively. The exposure levels in rat kidney and bladder were quite low. Conclusion: The active principles of Yizhi were specially distributed into gastrointestinal tissues after oral administration of its ethanol extract to rats. The tissue distribution behaviors partly supported its anti-diarrheal effects from a pharmacokinetic opinion. This paper will be useful as the starting point for studying the pharmacological activities of this traditional herb.