Forced degradation and impurity profiling: Recent trends in analytical perspectives

Favipiravir, remdesivir, and lopinavir: metabolites, degradation products and their analytical methods

Severe acute respiratory syndrome 2 (SARS-CoV-2) caused the emergence of the COVID-19 pandemic all over the world. Several studies have suggested that antiviral drugs such as favipiravir (FAV), remdesivir (RDV), and lopinavir (LPV) may potentially prevent the spread of the virus in the host cells and person-to-person transmission. Simultaneously with the widespread use of these drugs, their stability and action mechanism studies have also attracted the attention of many researchers. This review focuses on the action mechanism, metabolites and degradation products of these antiviral drugs (FAV, RDV and LPV) and demonstrates various methods for their quantification and discrimination in the different biological samples. Herein, the instrumental methods for analysis of the main form of drugs or their metabolite and degradation products are classified into two types: optical and chromatography methods which the last one in combination with various detectors provides a powerful method for routine and stability analyses. Some representative studies are reported in this review and the details of them are carefully explained. It is hoped that this review will be a good guideline study and provide a better understanding of these drugs from the aspects investigated in this study.

Electrophoresis, a transport technology that transitioned from moving boundary method to zone method

Gel electrophoresis, a transport technology, is one of the most widely used experimental methods in biochemical and pharmaceutical research and development. Transport technologies are used to determine hydrodynamic or electrophoretic properties of macromolecules. Gel electrophoresis is a zone technology, where a small volume of sample is applied to a large separation gel matrix. In contrast, a seldom-used electrophoresis technology is moving boundary electrophoresis, where the sample is present throughout the separation phase or gel matrix. While the zone method gives peaks of separating macromolecular solutes, the moving boundary method gives a boundary between solute-free and solute-containing phases. We will review electrophoresis as a transport technology of zone and moving boundary methods and describe its principles and applications.

HPLC and LC-MS/MS-Based Quantitative Characterization of Related Substances Associated with Sotalol Hydrochloride

In total, three related substances (RS) associated with sotalol hydrochloride (STHCl) were herein identified with a novel gradient high-performance liquid chromatography (HPLC) protocol. Further characterization of these substances was then performed via liquid chromatography-mass spectroscopy (LC-MS/MS) and nuclear magnetic resonance (NMR) approaches. For these analyses, commercial STHCl samples were used for quantitative HPLC studies and the degradation of STHCl under acidic (1M HCl), alkaline (1M NaOH), oxidative (30% H2O2), photolytic (4500 Lx), and thermal stress conditions (100 °C) was assessed. This approach revealed this drug to be resistant to acidic, alkaline, and high-temperature conditions, whereas it was susceptible to light and oxidation as confirmed through long-term experiments. The putative mechanisms governing RS formation were also explored, revealing that RS3 was derived from the manufacturing process, whereas RS2 was generated via oxidation and RS1 was generated in response to light exposure. The cytotoxicity of these RS compounds was then assessed using MTT assays and acute toxicity test. Overall, this study provides details regarding the characterization, isolation, quantification, and toxicological evaluation of STHCl and associated RS compounds together with details regarding the precise, specific, and reliable novel HPLC technique, thus providing the requisite information necessary to ensure STHCl purity and safety.

Separation and characterization of related substances of Lurasidone hydrochloride by LC-QTOF-MS techniques

In the present study, a reliable LC-QTOF-MS method was developed and employed for the separation and characterization of process-related substances and forced degradation products of Lurasidone hydrochloride. The chromatographic separation was carried out using an Agilent Poroshell 120 Bonus-RP C18 column (100 mm × 4.6 mm, 2.7 µm) and a mobile phase consisting of a gradient elution of 10 mM ammonium formate solution and methanol. The degradation studies followed the guidelines outlined in ICH Q1A (R2). It was observed that Lurasidone hydrochloride exhibited instability under photolytic, alkaline, and oxidative stress conditions, while remaining relatively stable under acidic and thermal stresses. Through positive ESI-QTOF mass spectrometric analysis, fourteen related compounds in total, including both process-related and stress degradation products, were identified based on the accurate masses of parent and product ions and calculated elemental compositions. Amongst these substances, nine had not been previously reported, and their formation mechanisms were speculated. The process-related substances were further confirmed by NMR spectra determination, and suggestions were proposed to eliminate them. This study highlights the potential for monitoring and controlling related substances during the manufacturing processes, providing valuable insights for process optimization and quality control of Lurasidone hydrochloride.

A critical assessment on stability behaviour of Vorinostat using LC-MS-QTOF with H/D exchange and NMR

Vorinostat is the first USFDA-approved HDAC inhibitor for the treatment of cutaneous t-cell lymphoma. Vorinostat was exposed to ICH-recommended hydrolytic (acid, base, and neutral), oxidative, thermal, and photolytic stress conditions to understand the degradation behaviour. A Stability indicating LC method was developed and validated for separating and identifying forced degradation products. Under different stress conditions, six degradants were identified and characterized by LC-HRMS, MS/MS, and hydrogen-deuterium exchange mass studies. Vorinostat was found to be highly susceptible to the acidic and basic environment. In contrast, the drug substance was stable in the solid state under thermal and photolytic conditions whereas, it was found moderately stable when photolytic stress was provided to dissolved state of Vorinostat in acetonitrile-water. The degradants were identified as 7-amino-N-phenylheptanamide, 8-hydrazineyl-8-oxo-N-phenyloctanamide, 8-oxo-8-(phenylamino)octanoic acid, 8-oxo-8-(2-(7-oxo-7-(phenylamino)heptyl)hydrazineyl)-N-phenyloctanamide, 8,8'-(1-hydroxyhydrazine-1,2-diyl)bis(8-oxo-N-phenyloctanamide), and N1-((8-oxo-8-(phenylamino)octanoyl)oxy)-N8-phenyloctanediamide. The mechanistic explanation for the formation of each degradant in stability conditions has also been derived. The major degradants were also isolated/synthesized and characterized through 1H NMR for preparing impurity standards. Additionally, in-silico toxicity of the degradants was predicted in comparison to the drug, to identify whether any degradant has any specific type of toxicity and requires special focus to set specification limits during formulation development. The predicted toxicity indicated that the degradants have similar safety profile as that of the drug and specification can be set as per general impurity guideline.

OMNI: Gas Chromatograph Captures Seven Common PET Radiotracer Analytes in under 5 Minutes

A novel gas chromatography method was developed using automatic injections to identify and quantify the amount of residual solvents or analytes in samples of fluorine-18 and carbon-11 radiopharmaceuticals. This approach evaluates seven analytes in less than 5 versus 13 min of acquisition time. The method additionally includes a 3 min bakeout to aid in the removal and carry-over of higher-boiling impurities. Chromatographic parameters such as column temperature, hold time, column pressure, flow rate, and split ratios were adjusted and optimized to analyze radioactive drug samples containing analytes which include methanol, ethanol, acetone, acetonitrile, triethylamine, N,N-dimethylformamide, and dimethyl sulfoxide. The relative standard deviation for each solvent was determined to be no greater than 1.6%. The method limit of detection (LOD) and limit of quantification (LOQ) were between 0.053 and 0.163 and 0.000 (5.791 × 10-6) and 0.520 mg/mL, respectively. This GC technique, using flame ionization detection (FID), was validated and is currently employed for the routine quality control of all approved IND and RDRC PET radiopharmaceuticals at our center.

Selective Stability Indicating Liquid Chromatographic Method Based on Quality by Design Framework and In Silico Toxicity Assessment for Infigratinib and Its Degradation Products

Infigratinib, a protein kinase inhibitor employed in the therapeutic management of cholangiocarcinoma, was subjected to various stress conditions, including hydrolytic (acidic and alkaline), oxidative, photolytic, and thermal stress, in accordance with the rules established by the International Council for Harmonization. A cumulative count of five degradation products was observed. The application of the Quality by Design principle was utilized in the development of a rapid and specific separation method for Infigratinib and its degradation products. The methodology employed in this study was derived from an experimental design approach, which was utilized to examine the critical process parameters associated with chromatographic systems. The reversed-phase high-performance liquid chromatography technique, employing a C18 column and a mobile phase composed of a gradient mixture of 25 mM ammonium acetate buffer at pH 6.0 and acetonitrile, successfully facilitated the chromatographic separation. The methodology was expanded to include the utilization of UPLC-quadrupole tandem mass spectrometry in order to conduct a comprehensive analysis of the structural properties and characterize the degradation products. Overall, five degradation products were found in different stress conditions. The method was verified at certain working points, wherein a linearity range (5.0-200.0 µg/mL) was developed and other parameters such as accuracy, repeatability, selectivity, and system suitability were evaluated. Finally, the toxicity and mutagenicity of Infigratinib and its degradation products were predicted using in silico software, namely DEREK Nexus® (version 6.2.1) and SARAH Nexus® (version 3.2.1). Various toxicity endpoints, including chromosomal damage, were predicted. Additionally, two degradation products were also predicted to be mutagenic.

Novel Iron Oxide Nanoparticle-Fortified Carbon Paste Electrode for the Sensitive Voltammetric Determination of Atomoxetine

Herein, the fabrication and full characterization of a novel atomoxetine (ATX) voltammetric carbon paste electrode (CPE) fortified with iron oxide nanoparticles (FeONPs) is demonstrated. Modification of the carbon paste matrix with the metallic oxide nanostructure provides proper electrocatalytic activity against the oxidation of ATX molecules at the carbon paste surface, resulting in a noticeable improvement in the performance of the sensor. At the recommended pH value, ATX recorded an irreversible anodic peak at 1.17 V, following a diffusion-controlled reaction mechanism. Differential pulse voltammograms exhibited peak heights linearly correlated to the ATX content within a wide concentration range from 45 to 8680 ng mL^-1, with the limit of detection reaching 11.55 ng mL^-1. The electrooxidation mechanism of the ATX molecule was proposed to be the oxidation of the terminal amino group accompanied by the transfer of two electrons and two protons. The fabricated FeONPs/CPE sensors exhibited enhanced selectivity and sensitivity and therefore can be introduced for voltammetric assaying of atomoxetine-indifferent pharmaceutical and biological samples in the presence of its degradation products and metabolites.

Development of tandem-column liquid chromatographic methods for pharmaceutical compounds using simulations based on hydrophobic subtraction model parameters

The liquid chromatography (LC) analysis of small molecule pharmaceutical compounds and related impurities is crucial in the development of new drug substances, but developing these separations is usually challenging due to analyte structural similarities. Tandem-column LC (TC-LC) has emerged as a powerful approach to achieve alternative separation selectivity compared to conventional single column separations. However, one of the bottlenecks associated with use of tandem column approaches is time-consuming column pair screening and selection. Herein, we compared critical resolution (R_c) in single column vs. TC-LC separations for a given set of small molecule pharmaceutical compounds and developed a column selection workflow that uses separation simulations based on parameters from the hydrophobic subtraction model (HSM) of reversed-phase selectivity. In this study, HSM solute parameters were experimentally determined for a small molecule pharmaceutical (Linrodostat) and ten of its related impurities using multiple linear regression of their retentions on 16 selected RPLC columns against in-house determined HSM column parameters. R_c values were calculated based on HSM database column parameters for a pool of about 200 available stationary phases in both single-phase column (2.1 mm i.d. × 100 mm) or tandem column paired (two 2.1 mm i.d. × 50 mm) formats. Four column configurations (two single and two tandem) were predicted to achieve successful separations under isocratic HSM separation conditions, with a fifth tandem pair predicted to have a single co-elution. Of these five potential candidates, one tandem pair yielded compete baseline resolution of the 11-component mixture in an experimental separation. In this specific case, the tandem column pairs outperformed single-phase columns, with better predicted and experimental R_c values for the Linrodostat mixture under the HSM separation conditions. The results reported in this study demonstrated the enormous selectivity potential of TC-LC in pharmaceutical compound separations and are consistent with our previous study that examined the potential of tandem column approaches using purely computational means, though there is room for substantial improvement in the prediction accuracy. The proposed workflow can be used to prioritize a small number of column combinations by computational means before any experiments are conducted. This is highly attractive from the point of view of time and resource savings considering over 200,000 different tandem column pairings are possible using columns for which there are data in the HSM database.

Characterisation of degradation products of tegoprazan by LC-MS and GC-MS

Tegoprazan is a novel orally active potassium-competitive acid blocker (P-CAB), capable of binding to the K⁺ binding site of H⁺/K⁺-ATPase in a reversible way to inhibit gastric acid secretion. Tegoprazan has been approved for treating acid-related diseases. In this study, stress testings of tegoprazan were performed under various conditions, including hydrolysis (acidic, alkaline, and neutral), oxidation, photolysis, and thermal stress. Tegoprazan showed instability in acidic, alkaline, and oxidative conditions. Eight degradation products (DPs) were identified. The DPs were characterized by LC-HRMS, LC-MSⁿ, or GC-Q-TOF-MS. Meanwhile, DP-1, DP-2 and DP-3 were successfully synthesized and confirmed by NMR. The degradation pathway of tegoprazan was summarized. To the best of our knowledge, this is the first study on the forced degradation of tegoprazan.

A Novel Validated UHPLC Method for the Estimation of Rosuvastatin and Its Complete Impurity Profile in Tablet Formulations

A key step in the development of medicinal products is the research and validation of selective and sensitive analytical methods for the control of impurities from synthesis and degradation. As most impurities are similar in structure to the drug substance, the achievement of chemo-selective conditions is usually challenging. Herein, a direct and highly selective ultra-high-performance liquid chromatographic method for determining the assay and related substances content in medicinal products containing rosuvastatin calcium salt (RSV) is presented. RSV is used to treat high cholesterol levels and prevent heart attacks and strokes. The most engaging feature of this method was the baseline separation of all organic related substances listed in the European Pharmacopoeia (EP) monograph for the RSV tablets, achieved for the first time in less than 15 min using the Acquity BEH C18 (100 mm × 2.1 mm, 1.7 μm) column under reversed-phase isocratic conditions. The mobile phase adopted for the chemo-selective analysis does not contain buffers but instead contains trifluoroacetic as an acid additive. The chromatographic method was validated according to the guidelines of the International Conference on Harmonization (ICH) and proved to be linear, precise and accurate for determining the content of RSV and related chiral substances in tablet formulations.

Recent Progresses in Analytical Perspectives of Degradation Studies and Impurity Profiling in Pharmaceutical Developments: An Updated Review

Forced degradation studies have been used to simplify analytical methodology development and achieve a deeper knowledge about the inherent stability of active pharmaceutical ingredients (API) and drug products. This provides insight into degradation species and pathways. Identification of impurities in pharmaceutical products is closely related to the selection of the most appropriate analytical methods like HPLC-UV, LC-MS/MS, LC-NMR, GC-MS, and capillary electrophoresis. Herein, recent trends in analytical perspectives during 2018-April 14, 2021, are discussed based on forced and impurity degradation profiling of pharmaceuticals. Literature review showed that several methods have been used for experimental design and analysis conditions such as matrix type, column type, mobile phase, elution modes, detection wavelengths, and therapeutic category. Thus, since these factors influence the separation and identification of the impurities and degradation products, we attempted to perform a statistical analysis for the developed methods according to the abovementioned factors.

Using thermal forced degradation approach for impurity profiling of budesonide solution-formulated metered dose inhalation with implementation of LC-QTOFMS and HPLC-UV

The impurity profile of budesonide solution-formulated metered dose inhalation using thermal forced degradation approach was studied intensively in this article. The structural identification of 10 budesonide related impurities was conducted by LC-QTOFMS, and the impurity level in the formulations of different excipients and packing materials were compared using HPLC-UV. Based on our results, the impurities were classified into three groups: (Ⅰ) process impurities, including budesonide impurity A, C and F; (Ⅱ) degradation products, including budesonide impurity E, G, D, 17-carboxylate, and 17-ketone; (Ⅲ) not only process impurities but also degradation products, including budesonide impurity I and L. Budesonide impurity D, 17-carboxylate, 17-ketone and impurity L were found to be the major degradation products of budesonide, and the reaction pathways for the generation of these impurities were speculated. The generation of budesonide impurity D, 17-carboxylate and L was found to be an aerobic oxidation process induced by Al₂O₃ on the inner surface of aluminum canisters. Furthermore, an in-depth discussion on the proposed impact of the excipients on budesonide degradation, especially on the Al₂O₃-induced oxidation process, was provided in this article.

Stability-indicating Liquid Chromatography Method Development and Validation for Impurity Profiling of Montelukast Sodium in Bulk Drug and Tablet Dosage Form

Montelukast sodium (MLS) is a leukotriene receptor antagonist drug used in the treatment of asthma, bronchospasm, allergic rhinitis and urticaria. A reversed-phase high performance liquid chromatography method was developed to separate, identify and quantitative determination of MLS and its eight known organic impurities in tablet dosage form using C₁₈ column and mobile phases consisting of gradient mixture of pH 2.5 phosphate buffer and acetonitrile. Stability-indicating character of the developed method was proven using stress testing (1N HCl at 80°C/30m, 1N NaOH at 80°C/30m, H₂ O at 80°C/30m, 3% H₂ O₂ at 25°C/1m, dry heat at 105°C/10h and UV-Vis light/4days) and was validated for specificity, quantitation limit, linearity, precision, accuracy and robustness. For MLS and its eight known impurities, the quantitation limits, linearity and recoveries were found in a range of 0.015 - 0.03 μg/mL, correlation coefficient (r) > 0.997 (R² > 0.995) and 85.5% to 107.0%, respectively. The developed chromatographic method is suitable for impurity profiling and also for assay determination of MLS in bulk drugs and pharmaceutical formulations. The mass values (m/z) of newly formed degradation products (DP1 and DP2) of montelukast sodium were identified by using the liquid chromatography-mass spectrometry (LC-MS).

The degradation map process - a tool for obtaining a lean stability strategy in drug development

Stability is fundamental when exploring a drug candidate's potential as a drug product. During the pharmaceutical industry drug development process information regarding stability and degradation are captured in different departments, e.g. from discovery to operations, and will be included in the overall control strategy. With a profound understanding of a drug candidate's degradation chemistry, a science and risk based approach in progressing a lean stability strategy is possible. This case study present a clear and visible concept to facilitate a lean stability strategy by the use of degradation maps and describes a process for how these can be used during drug development. The understanding of possible and/or observed degradation pathways will guide the design of the drug product and stability studies in development. A degradation map displays degradation pathways with short comments on the reaction/mechanism involved. The degradation map process starts with a theoretical degradation map. The map is updated as the drug project progresses, preferably after forced degradation experiments, after compatibility studies and finally when the late stage formulation is set. The degradation map should be used to capture information of intrinsic chemical properties of the active pharmaceutical ingredient (API) and can thereby be used to mitigate stability issues. The map is foremost a cross-functionally available tool collecting and visualizing stability information throughout the development process, and as such a valuable tool to efficiently develop a lean stability strategy.

Impurity profiling and stability-indicating method development and validation for the estimation of assay and degradation impurities of midostaurin in softgel capsules using HPLC and LC-MS

Midostaurin (MDS) is used for the treatment of acute myeloid leukemia, myelodysplastic syndrome, and advanced systemic mastocytosis. MDS softgel capsule samples were subjected to stress testing per International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use guidelines for impurity profiling study. MDS underwent extensive degradation under stress testing (acid, alkaline, oxidative, photolytic, thermolytic, and hydrolysis conditions) and formed four degradation products (DPs). MDS and its DPs were separated well from one another with good resolution using reserved-phase HPLC using an Inertsil ODS-3V column (250 × 4.6 mm, 5 μm) and a mobile phase of ammonium formate (40 mM) and acetonitrile. The stability-indicating characteristic of the newly developed method was proven for the estimation of MDS assay, and its organic impurities were free from interference. The validated method exhibited excellent linearity, accuracy, precision, specificity, detection limit, and quantitation limit within 25 min run time. Stress testing, robustness, and solution stability were performed to ensure the continuous performance of the developed method. The peak fractions of DPs formed under stress testing were isolated and characterized using LC-MS, ¹ H and ¹³ C NMR, IR, and UV-Vis. The structure of the major DPs was predicted as DP1 based on the spectral data. The proposed method is effectively used for MDS in bulk drug and finished formulations in the pharmaceutical industry.

A novel method for the quantification of anlotinib in human plasma using two-dimensional liquid chromatography

A simple, efficient, and stable detection method of two-dimensional liquid chromatography (2D-LC) was established and validated to determine anlotinib in the human plasma. The 2D-LC system comprises a first-dimensional column (LC1), an intermediate transfer column, and a second-dimensional column (LC2). With simple protein precipitation treatment, the samples were processed directly for detection. The analysis cycle time was completed within 9.50 min. For the anlotinib concentrations, the calibration curve was linear over the 5.00-320.00 ng/mL range. The intra-day and inter-day precision ranges were 0.77-6.22% and 1.92-4.26%, respectively, for anlotinib concentrations. The recoveries were in the range of 97.85-102.50%. A total of 135 plasma samples from 94 patients were analyzed by our method. The plasma concentrations of patients were in the range of 5.17-106.38 ng/mL, in which the female had a higher plasma concentration (6.44-106.38 ng/mL). The simultaneous application of dexamethasone can increase the anlotinib concentration in the plasma. In our clinical application, we found that the factors that affect the plasma concentration include the time and dose of the medication, gender, and drug interactions. The method appears to be sensitive, precise, selective, and suitable for determining the concentration of anlotinib in the plasma sample.

A stability-indicating HPLC method for estimation of doxylamine succinate in tablets and characterization of its major alkaline stress degradation product

Background

A new selective rapid RP-HPLC-DAD method was developed and evaluated for the quantification of doxylamine succinate (DOX) in bulk and pharmaceutical dosage form. The separation of DOX at different degradation conditions was achieved with a Kromasil C18 (4.6 × 250 mm, 5-μm particle size). The mobile phase employed comprised of phosphate buffer (pH 3.5) and methanol in the ratio of 45:55 v/v. The flow rate was kept maintained at 1.0 ml/min and eluents were detected at 262 nm. The drug was subjected to different stress conditions like acid, base, neutral, hydrolysis, oxidation, photolysis, and thermal degradation. The analytical performance of the proposed HPLC method was thoroughly validated in terms of linearity, precision, accuracy, specificity, robustness, detection, and quantification limits.

Results

The method produces linear responses that were found in the range of 10–50 μg/ml. The regression equation was found to be Y = 42984x − 10260. The correlation coefficient was found to be 0.9998. The LOD and LOQ for DOX were found to be 0.96 and 3.28 μg/ml, respectively. The short-term solution stability of DOX (100 μg/ml) was evaluated under (25 ± 2°C) storage condition and found to be 98.82 to 101%. The percentage recovery for DOX was in the range of 99.73 to 99.91%. The obtained results of the stress degradation study and peak purity data indicate the potential of the developed HPLC method to resolve degradants from DOX peak. The major alkaline degradation product was isolated using preparative chromatographic technique and extensive FT-IR was performed to ascertain the structure of the alkaline degradant.

Conclusion

It was concluded that the proposed method was simple, sensitive, accurate, cost-effective, and less time-consuming for the quantification of DOX. This method was successfully utilized for stability testing of commercially available DOX tablets. Hence, the proposed method can be applied for routine quality control of DOX in bulk drug as well as in marketed formulations.

Rotigotine: A Review of Analytical Methods for the Raw Material, Pharmaceutical Formulations, and Its Impurities

BACKGROUND

Rotigotine is a dopaminergic agonist developed for the treatment of Parkinson's disease and restless leg syndrome. The pure levorotatory enantiomer is marketed in several countries as a transdermal patch. Reports of oxidation and instability in a previous formulation indicate the need to evaluate impurities in both the raw material and pharmaceutical dosage forms of rotigotine to ensure product quality.

OBJECTIVE

This review examines the main analytical methods for analyzing rotigotine in raw material and its transdermal patches with the aim of assisting the development of new pharmaceutical formulations and stability studies.

METHODS

Analytical methods based on high-performance liquid chromatography for rotigotine from pharmacopoeias and literature were evaluated. A comparison was made between the methods found in the literature and official rotigotine monographs described by the United States, European, and British Pharmacopoeias, including a discussion of their acceptance limits for impurities related to the drug. The different impurities from the synthesis processes and degradation studies of rotigotine were also evaluated, as well as the main articles that describe methods for assessing their chiral purity.

RESULTS

Qualified and unofficial official impurities found in forced degradation studies were verified. The methods presented show adequate specificity and selectivity in determining the drug in the presence of its impurities.

CONCLUSIONS

The approached methods are promising, but more detailed studies on the stability of rotigotine are still lacking, mainly in the pharmacokinetic and toxicological characterization of its impurities.

A rapid RP-HPLC stability-indicating method development and validation of moxifloxacin hydrochloride-related substances in finished dosage forms

A reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for the identification and quantification of moxifloxacin hydrochloride-related substances in finished dosage forms. Chromatographic separation was achieved on an Agilent C18 column (150 × 4.6 mm, 5 μm) with the mobile phase (0.01 M potassium dihydrogen orthophosphate as buffer and methanol in the ratio of 70:30) eluted in isocratic mode. The HPLC flow rate was 1.0 mL min^-1 , and peaks were monitored at 230 nm using a photodiode array (PDA) detector. The column temperature was kept constant at 30°C, and the injection volume was 10 μL. The run time of the method was 16 min. The method was validated as per the International Conference on Harmonization (ICH) guidelines. Linearity was recorded at various concentrations ranging from 0.25 to 1.5 μg mL^-1 for all the moxifloxacin impurities. Linearity, regression value, recovery, %relative standard deviation (RSD) of method precision values were found within the acceptance limits. The method for related substances (RS) in moxifloxacin was found to be specific, linear, accurate, precise, rugged, and robust. The validated method was suitable for the quantification of the RSs in moxifloxacin drug products. The method was applied in quality control lab for the analysis of moxifloxacin impurities in stability analysis.

Analytical quality by design in the development of a solvent-modified micellar electrokinetic chromatography method for the determination of sitagliptin and its related compounds

A solvent-modified micellar electrokinetic chromatography method was developed following the Quality by Design approach for the simultaneous determination of sitagliptin (SIT), an oral antihyperglycemic drug, and its main impurities derived from the synthesis process. The separation system was identified in the scouting phase and was made by sodium dodecyl sulphate (SDS) micelles with the addition of n-butanol and methanol. The knowledge space was investigated through an asymmetric screening matrix, taking into consideration eight critical method parameters (CMPs) involving the composition of the background electrolyte in terms of buffer concentration and pH, the concentration of surfactants and organic modifiers, and voltage. The critical method attributes (CMAs) were identified as analysis time and the distance between the tail of the electroosmotic flow system peak and the front edge of impurity I₁ (sitagliptin triazole hydrochloride). A Box-Behnken Design was used in response surface methodology for calculating the quadratic models relating the CMPs to the CMAs. From the models it was possible to compute the method operable design region (MODR) through Monte-Carlo simulations. The MODR was identified in the probability maps as the multidimensional zone where the risk of failure to achieve the desired values for the CMAs was lower than 10 %. The experimental conditions corresponding to the working point, with the MODR interval, were the following: background electrolyte, 14 (10-18) mM borate buffer pH 9.20, 100 mM SDS, 13.6 (11.1-16.0) %v/v n-butanol, 6.7 (4.5-8.8) %v/v methanol; voltage and temperature were set to 28 kV and 22 °C, respectively. The developed CE method was validated in accordance with International Council for Harmonisation guidelines and was applied to the analysis of SIT tablets. The routine analysis for the quality control of the pharmaceutical product could be conducted in about 11 min.

Stability Indicating Methods for Determination of Third Generation Antiepileptic Drugs and Their Related Substances

The third generation of antiepileptic drugs that have been approved by international regulatory agencies between 2007 and 2018 include rufinamide, stiripentol, eslicarbazepine acetate, lacosamide, perampanel, brivaracetam and everolimus. As part of demonstrating their safety profile, stability indicating methods are developed to monitor these drugs and their impurities. In this context, this review describe some characteristics, impurities and the stability indicating methods used for the determination of these drugs and the presence of their related substances. Through a search in official compendia and scientific articles, fifty-six analytical methodologies were identified up to October 2020. The methodologies were developed using techniques of HPLC, UPLC, HPTLC, GC and UV/Vis spectrophotometry. A majority of the methods (∼70%) employed HPLC-UV. A number of these antiepileptic drugs were found to have had a small number of studies related to their stability and for the detection of impurities. The presentation of the current level of research on third generation antiepileptic drugs highlights the need for new stability and safety studies that are necessary to develop new pharmaceutical products containing these drugs.

Appraisal of the greenness profile of a chromatographic method for the simultaneous estimation of carbamazepine and oxcarbazepine, along with two potential impurities and three formulation excipients

Structurally related carbamazepine (CBZ) and oxcarbazepine (OX) are two of the most commonly used antipsychotic drugs. The main impurities of CBZ, as described in both the USP and the BP, are iminodibenzyl (IMD) and iminostilbene (IST). Meanwhile, for non-pharmacopeial OX, the declared impurities include CBZ and IST. Prescribed oral suspensions of CBZ and OX contain additives including methyl paraben (MP), propyl paraben (PP) and sorbic acid (SA) as preservatives. An HPTLC method was introduced and developed for resolving the interference between CBZ, OX, their impurities, and the suspension additives in a single run, in addition to their quantitation with a high sensitivity that satisfies the USP requirements for the detection and quantitation of drug impurities. In the developed HPTLC method, CBZ and OX were measured in the range of 40–4000 ng per band, while IMD, IST, MP, PP and SA were in the range of 20–2000 ng per band, using a mixture of hexane : ethylacetate : formic acid : acetic acid (8 : 2 : 0.5 : 0.3, by volume) and UV scanning at 254 nm. The greenness profile of the method was evaluated by two different tools, the analytical Eco-Scale and the Green Analytical Procedure Index (GAPI), then a comparison between their results was conducted. This is the first time that the studied drugs, along with their impurities and suspension additives, were analyzed by a HPTLC method in a single run and within the limits required by the USP guidelines.

Structurally related carbamazepine (CBZ) and oxcarbazepine (OX) are two of the most commonly used antipsychotic drugs.

Identification and characterization of degradation products of indacaterol using liquid chromatography/mass spectrometry

Indacaterol (IND), 5-[2-[(5,6-Diethyl-2,3-dihydro-1H-inden-2-yl)amino]-1-hydroxyethyl]-8-hydroxyquinolin-2(1H)-one, is an active pharmaceutical ingredient (API) which is used to treat chronic obstructive pulmonary disease (COPD). We followed the International Council for Harmonization (ICH) guide lines to study the degradation behavior of IND under various stress conditions. Stressed degradation of the drug was performed under hydrolytic (alkaline, acidic and neutral), photolytic, oxidative and thermal conditions. Identification and characterization of IND and its forced degradation products (DPs) were demonstrated by using LC-HRMS and MS/MS method. A total of three DPs (DP1-DP3) were identified and characterized. The IND was found to be stable under photolytic, oxidative and thermal conditions, whereas it produced three DPs in acidic, basic and neutral hydrolytic stress conditions.

Capillary electrophoretic methods for quality control analyses of pharmaceuticals: A review

Capillary electrophoresis represents a promising technique in the field of pharmaceutical analysis. The presented review provides a summary of capillary electrophoretic methods suitable for routine quality control analyses of small molecule drugs published since 2015. In total, more than 80 discussed methods are sorted into three main sections according to the applied electroseparation modes (capillary zone electrophoresis, electrokinetic chromatography, and micellar, microemulsion, and liposome-electrokinetic chromatography) and further subsections according to the applied detection techniques (UV, capacitively coupled contactless conductivity detection, and mass spectrometry). Key parameters of the procedures are summarized in four concise tables. The presented applications cover analyses of active pharmaceutical ingredients and their related substances such as degradation products or enantiomeric impurities. The contribution of reported results to the current knowledge of separation science and general aspects of the practical applications of capillary electrophoretic methods are also discussed.

UPLC-ESI/Q-TOF MS/MS Method for Determination of Vildagliptin and its Organic Impurities

Vildagliptin (VLG) corresponds to a drug used for the treatment of diabetes mellitus. This disease requires continuous treatment, and so the control of impurities present in it is important to assure the quality of this drug. Thus, it is necessary to use sensitive and selective detection techniques and the ultra-performance liquid chromatography is a better option compared with high-performance liquid chromatography because it enhances the separation efficiency with a shorter analysis time and an increased resolution. This research analysis was accomplished by using liquid chromatography/tandem mass spectrometry, and the quantification was performed by using an extracted ion from the VLG drug and its main organic impurities of synthesis. During the validation process, following international standards, the method proved to be linear for the tree substances (R2 = 0.997-0.998) and the analysis of variance showed a non-significant linearity deviation (P > 0.05). Three critical factors were selected to evaluate method robustness with a full factorial experimental design, and the changes in the parameters were found to be not significant for the quantification of VLG and its impurities. The ultra-performance liquid chromatography-tandem mass spectrometry for the determination of impurities in VLG was precise, accurate and robust proving to be effective for analysis in the pharmaceutical industry and to improve the quality, safety and effectiveness of the new drug developed.

Development of a Stability-Indicating Analytical Method for Determination of Venetoclax Using AQbD Principles

Venetoclax is an emerging drug for the treatment of various types of blood cancers. It was first approved in 2016 for the treatment of relapsed and refractory chronic lymphocytic leukemia. Later, the indications expanded, and multiple research as well as clinical studies are still conducted involving venetoclax. No analytical method for the determination of venetoclax can currently be found in the literature. We developed a mass spectrometry-compatible stability-indicating ultrahigh-performance liquid chromatography (LC) method for venetoclax. The LC method was developed using analytical quality by design principles. The developed method is able to separate venetoclax and its degradation products. The method was validated in the working point where a linearity range was established and accuracy, repeatability, and selectivity were assessed. Venetoclax is the only Bcl-2 protein inhibitor on the market. It is very effective in combinational therapy, so future drug development involving venetoclax may be expected. A stability-indicating method could aid in the development of new pharmaceutical products with venetoclax.

Intrinsic Stability Study and Forced Degradation Profiling of Olopatadine Hydrochloride by RP-HPLC-DAD-HRMS Method

Objectives

Forced degradation determines the intrinsic stability of a molecule by establishing degradation pathways in order to identify the likely degradation products (DPs). The objective of the present research was to establish intrinsic stability and forced degradation profiling of olopatadine hydrochloride.

Materials and Methods

The intrinsic stability of olopatadine hydrochloride was evaluated by RP-HPLC, where a mixture of 0.1% formic acid and organic phase (methanol:acetonitrile; 50:50 % v/v) was used as mobile phase at 1.0 mL/min in gradient mode. Different stress conditions were employed to explore the intrinsic stability of olopatadine hydrochloride.

Results

In acidic condition, five DPs, i.e. OLO1, OLO2, OLO3, OLO4, and OLO5, were observed. OLO5 was the major DP that increased with time and the peak area of OLO was decreased. In addition to OLO3 and OLO5, two more DPs were observed in alkaline condition, i.e. OLO6 and OLO7. OLO5 and OLO6 were two major DPs; OLO5 increased with time while OLO6 had a zigzag pattern of peak area with time. All DPs of neutral condition were also found in acidic condition while OLO3 and OLO5 were common in all three types of hydrolytic degradation.

Conclusion

Thus, OLO has similar pattern of degradation profiling in all hydrolytic conditions (acidic, alkaline, and neutral). No degradation was found in thermal, ultraviolet light, or oxidative conditions over 10 days. OLO-Imp was recognized as an analogue structure of OLO and proposed as 11-[(3-dimethylamino)-propylidene]-6,11-dihydro-dibenz[b,e]oxepin-2-propanoic acid in standard drug. OLO1 was identified as (2-(4-(dimethylamino) butyl) phenyl)methanol, which may be formed by cleavage of the tricyclic ring in neutral condition.

A Validated RP-HPLC Stability Method for the Estimation of Chlorthalidone and Its Process-Related Impurities in an API and Tablet Formulation

Low-dose thiazide and thiazide-like diuretics are widely used as first-line therapy for hypertension. Chlorthalidone, a monosulfamyl diuretic, is frequently prescribed in cases of hypertension and congestive heart failure. In this research paper, an improved reverse-phase HPLC method was developed for the simultaneous identification and quantitation of pharmacopoeia-listed and in-house process- and degradation-related impurities of chlorthalidone in bulk drug and formulations. Chromatographic separation was carried out on a C₈ column (250 × 4.6 mm; '5 μm particle size) at a flow rate of 1.4 mL/min with a 220 nm detection wavelength. Mobile phase A consisted of buffer solution (diammonium hydrogen orthophosphate (10 mM, pH 5.5)) and methanol at a 65 : 35 ratio (v/v), and mobile phase B consisted of buffer solution and methanol at a 50 : 50 ratio (v/v). The API and formulation were subjected to stress conditions such as acid, alkali, oxidation, thermal, and photolytic conditions. Validation studies for the in-house process impurities were performed for specificity, limit of detection (LOD), limit of quantitation (LOQ), linearity, precision, accuracy, and robustness. Thus, an improved RP-HPLC method capable of good separation of all known and unknown impurities with acceptable resolution and tailing factor was developed.

Efficient and Straightforward Syntheses of Two United States Pharmacopeia Sitagliptin Impurities: 3-Desamino-2,3-dehydrositagliptin and 3-Desamino-3,4-dehydrositagliptin

Various organic impurities (starting materials, reagents, intermediates, degradation products, by-products, and side products) could be present in active pharmaceutical ingredients affecting their qualities, safeties, and efficacies. Herein, we present the efficient syntheses of two United States Pharmacopeia impurities of an antidiabetic drug sitagliptin, a potent and orally active dipeptidyl peptidase IV inhibitor: 3-desamino-2,3-dehydrositagliptin and 3-desamino-3,4-dehydrositagliptin. Our three-step synthetic approach is based on the efficient cobalt-catalyzed cross-coupling reaction of 1-bromo-2,4,5-trifluorobenzene and methyl 4-bromocrotonate in the first step, followed by hydrolysis of corresponding ester with 3 M HCl to (E)-(2,4,5-trifluorophenyl)but-2-enoic acid in high overall yield, whereas the reaction with 3 M NaOH resulted in the carbon-carbon double bond regio-isomerization and hydrolysis to give the (E)-(2,4,5-trifluorophenyl)but-3-enoic acid in 92% yield. Both acid derivatives were converted to title compounds via the amide bond formation with 3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine. Extensive screening of coupling/activation reagents, bases, and solvents reviled that the amide bond is formed the most efficiently using the (COCl)2/Et3N in THF or alternatively EDC/NMM/(DMAP or HOBt) in DMF obtaining the title compounds in 68-76% yields and providing the overall yields for the three-step process in the range of 57-64% on a gram scale. The presented study also demonstrates the importance of a proper selection of solvent, base, and coupling/activating reagent for amide bond formation using Michael acceptor-type allylbenzene derivatives as coupling partners to minimize the carbon-carbon double bond regio-isomerization.

Determination of Hydrochlorothiazide and Two Major Degradation Products by Stability Indicating High Performance Liquid Chromatography

Background:

Hydrochlorothiazide (HCTZ) is a thiazide diuretic which comprises two sulfonamide groups. The literature is not clear regarding the identification of the chromatographic peaks of its two major related substances: chlorothiazide and 4-amino-6-chloro-1,3-benzenedisulfonamide (DSA).

Methods:

In the present study, a simple, sensitive, and selective HPLC method was developed and validated for the assay of HCTZ, Chlorothiazide and DSA. The method was carried out on a C18 column, maintained at 40ºC. The mobile phase was composed of monobasic potassium phosphate buffer 0.02M pH 3.0/acetonitrile/methanol (82:9:9, v/v/v), run at a flow rate of 1.0 mL/min, and UV detection at 270 nm.

Results:

All related compounds including processing impurities and degradants from stressed samples were well separated from each other. The performance of this method was validated in accordance to the ICH guidelines and included specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness.

Conclusion:

Based on the results, the HCTZ degradation pathway was proposed and the validated HPLC method was successfully applied to the quantitative analysis of HCTZ in pharmaceutical formulations, contributing to improve quality control, to assure therapeutic efficacy and to clarify the literature.

In vitro toxic evaluation of two gliptins and their main impurities of synthesis

Background

The presence of impurities in some drugs may compromise the safety and efficacy of the patient’s treatment. Therefore, establishing of the biological safety of the impurities is essential. Diabetic patients are predisposed to tissue damage due to an increased oxidative stress process; and drug impurities may contribute to these toxic effects. In this context, the aim of this work was to study the toxicity, in 3 T3 cells, of the antidiabetic agents sitagliptin, vildagliptin, and their two main impurities of synthesis (S1 and S2; V1 and V2, respectively).

Methods

MTT reduction and neutral red uptake assays were performed in cytotoxicity tests. In addition, DNA damage (measured by comet assay), intracellular free radicals (by DCF), NO production, and mitochondrial membrane potential (ΔψM) were evaluated.

Results

Cytotoxicity was observed for impurity V2. Free radicals generation was found at 1000 μM of sitagliptin and 10 μM of both vildagliptin impurities (V1 and V2). A decrease in NO production was observed for all vildagliptin concentrations. No alterations were observed in ΔψM or DNA damage at the tested concentrations.

Conclusions

This study demonstrated that the presence of impurities might increase the cytotoxicity and oxidative stress of the pharmaceutical formulations at the concentrations studied.

Stability-indicating HPLC method for acyclovir and lidocaine in topical formulations

A simple, rapid and accurate stability-indicating HPLC assay was developed for the determination of acyclovir and lidocaine in topical formulations. Chromatographic separation of acyclovir and lidocaine was achieved using a reversed-phase C₁₈ column and a gradient mobile phase (20 mm ammonium acetate pH 3.5 in water and acetonitrile). The degradation products of acyclovir and lidocaine in the samples were analyzed by ultra performance liquid chromatography-time of flight mass spectrometry. The HPLC method successfully resolved the analytes from the impurities and degradation products in the topical formulation. Furthermore, the method detected the analytes from the human skin leachables following the extraction of the analytes in the skin homogenate samples. The method showed linearity over wide ranges of 5-500 and 10-200 μg/ml for acyclovir and lidocaine in the topical product, respectively, with a correlation coefficient (r² ) >0.9995. The relative standard deviations for precision, repeatability, and robustness of the method validation assays were <2%. The skin extraction efficiency for acyclovir and lidocaine was 92.8 ± 0.7% and 91.3 ± 3.2%, respectively, with no interference from the skin leachables. Thus, simultaneous quantification of acyclovir and lidocaine in the topical formulations was achieved.

Chemometrics Approaches in Forced Degradation Studies of Pharmaceutical Drugs

Chemometrics is the chemistry field responsible for planning and extracting the maximum of information of experiments from chemical data using mathematical tools (linear algebra, statistics, and so on). Active pharmaceutical ingredients (APIs) can form impurities when exposed to excipients or environmental variables such as light, high temperatures, acidic or basic conditions, humidity, and oxidative environment. By considering that these impurities can affect the safety and efficacy of the drug product, it is necessary to know how these impurities are yielded and to establish the pathway of their formation. In this context, forced degradation studies of pharmaceutical drugs have been used for the characterization of physicochemical stability of APIs. These studies are also essential in the validation of analytical methodologies, in order to prove the selectivity of methods for the API and its impurities and to create strategies to avoid the formation of degradation products. This review aims to demonstrate how forced degradation studies have been actually performed and the applications of chemometric tools in related studies. Some papers are going to be discussed to exemplify the chemometric applications in forced degradation studies.

Structure elucidation of novel degradation products of thiocolchicoside by NMR spectroscopy

Thiocolchicoside is a natural product analogue often used for its spasmolytic action. To know more about its stability under various stress conditions, the drug was stirred in acid, base and peroxide solutions. In acid hydrolysis, two products were obtained and in both, the glucose got cleaved. In one of them the acetyl group also got cleaved. A set of two diastereomers were formed during the peroxide mediated hydrolysis. The base mediated hydrolysis resulted in formation of three novel degradants. They have six membered rings in their structures instead of a seven membered cycloheptatrienone. Structures of known and novel degradation products have been elucidated by extensive analysis of HRMS, 1D and 2D NMR spectroscopic techniques.