Development of validated stability-indicating assay methods--critical review

Development and validation of stability-indicating HPLC method for assay of tonabersat in pharmaceutical formulations

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed to assay tonabersat and assess its stability in pharmaceutical formulations. Chromatographic separation was achieved using a Kinetex® C18 column (2.6 µm, 150 x 3 mm, 100 Å) at 50 °C, with a 20 µL injection volume. A linear gradient of acetonitrile in water (5 - 33.5 %) was applied for 1 min, followed by a gradual increase to 100 % over 26 min at a flow rate of 0.5 mL/min. Tonabersat and its degradation products were detected at 275 nm and 210 nm, respectively. The optimized method was used to evaluate stability of tonabersat in lipid-based pharmaceutical formulations at 5 ± 3 °C, 25 ± 2°C/60 ± 5 % RH, and 40 ± 2 °C/75 ± 5 % RH over 3 months. The method was validated as per ICH guidelines and demonstrated linearity in the range of 5 - 200 µg/mL (R2 = 0.99994) with good accuracy (98.25 - 101.58 % recovery) and precision (RSD < 2.5 %). The limit of detection and quantitation were 0.8 µg/mL and 5 µg/mL, respectively. Forced degradation studies showed significant degradation under alkaline (90.33 ± 0.80 %), acidic (70.60 ± 1.57 %), and oxidative stress (33.95 ± 0.69 %) at 70 °C, but no degradation was observed under thermal or photolytic stress. No chemical degradation was observed in either formulation on storage. Thus, the method was sensitive, specific, and suitable for stability testing of tonabersat in pharmaceutical formulations.

New stability indicating RP-HPLC methods for the determination of related substances and assay of trametinib acetic acid: a mass balance approach

New stability indicating related substances and assay methods for trametinib acetic acid by RP-HPLC have been developed and validated through forced degradation and mass balance studies for the first time. In related substances (RS) method, trametinib acetic acid was successfully separated from its six related substances namely, cyclopropanamide impurity, desiodo trametinib, desacetyl trametinib, trione acetamide intermediate, trione intermediate, and trione PTSA intermediate using YMC-Triart C18 (150 × 4.6 mm, 3 µm) column. Orthophosphoric acid (0.15%) in water was used as buffer. Gradient elution was programmed using mobile phase-A (buffer and acetonitrile mixture in 80:20 v/v ratio) and mobile phase-B (buffer and acetonitrile mixture in 20:80 v/v ratio). Acetonitrile and methanol mixture (1:1 v/v) was used as diluent. Flow rate, injection volume, column temperature, and wavelengths were kept as 0.8 mL/min, 10 µL, 55 °C, and 240 nm, respectively. Desacetyl trametinib and cyclopropanamide impurity were identified as potential degradation impurities in acid and base degradation conditions, respectively. Assay method specific to above six related substances was also developed. Assay of forced degradation samples was also determined, and the mass balance was established by adding total impurities formed in RS method to assay of trametinib acetic acid.

Development and validation of stability indicating assay method for mitapivat: Identification of novel hydrolytic, photolytic, and oxidative forced degradation products employing quadrupole-time of flight mass spectrometry

Mitapivat is a novel, first-in-class orally active pyruvate kinase activator approved by the US Food and Drug Administration in 2022 for the treatment of hemolytic anemia. There is no literature available regarding the identification of degradation impurities of mitapivat. The present study deals with the degradation behavior of mitapivat under various stress conditions such as hydrolytic, photolytic, thermal, and oxidative stress. The multivariate analysis found that the independent variables, that is, molarity, temperature, and time, are interacting with each other to affect the degradation of mitapivat. A specific, accurate, and precise high-performance liquid chromatographic (HPLC) method was developed to separate mitapivat from its degradation products. The separation was achieved on the C-18 column (250 mm × 4.6 mm × 5 µm) using the combination of 0.1% formic acid buffer and acetonitrile in gradient elution profile. The method was validated as per the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use Q2(R2) guideline. LC-electrospray ionization-Quadrupole-time of flight was employed to identify degradation products. A total of seven novel degradation products of mitapivat were identified based on tandem mass spectrometry and accurate mass measurement. In-silico toxicity of mitapivat and its degradation products was qualitatively evaluated by the DEREK toxicity prediction tool.

An Eco-Friendly RP-HPLC Method Development and Validation for Quantification of Favipiravir in Bulk and Tablet Dosage Form Followed by Forced Degradation Study

In this work, an eco-friendly simple, precise reverse phase high-performance liquid chromatography (HPLC) method has been developed and validated for Favipiravir in bulk and tablet dosage form followed by its force degradation study. The proposed method was validated to obtain official requirements including stability, accuracy, precision, linearity, robustness and selectivity as per International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) Guidelines. The estimation was developed on C (18) column reversed-phase using the mobile phase composition as methanol:water (10:90 v/v). The flow rate was set as 1 ml/min, and the maximum absorption was observed at 323 nm using Shimadzu Photo Diode Array detector. The Favipiravir, drug showed a precise and good linearity at the concentration ranges of 10-50 μg/mL. The Revearse Phase High Perforance Liquid Chromatography assay showed the highest purity ranging from 99.90 to 100.02% for Favipiravir, tablet dosage form, and 100.15% was the mean percentage purity. The percent recovery was found within the acceptance limit of (98.6-100.0%). Intra- and inter-day precision studies of the method were less than the maximum allowable limit percentage of relative standard deviation ≤ 2.0. The Favipiravir retention time was found to be 5.00 min. To examine the stability of the drug, various forced degradation studies were conducted on Favipiravir Active Pharmaceutical Ingredient. The developed method was validated according to the ICH guidelines. A very quick, cost-effective, precise and accurate HPLC method for the determination of Favipiravir has been developed and validated in compliance with ICH guidance Q2.

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.

A strategic approach towards mass balance investigations in pharmaceutical drug substance release testing: A peculiar out of specification case study encountered during API manufacture

Mass balance in drug substances release testing is a critical quality attribute in pharmaceutical manufacturing that continues to challenge modern analytical characterization. This specific perspective of mass balance is lacking in literature, and the following work addresses the knowledge gap related to this topic by examining an in-depth case study and detailing the systematic investigation into mass imbalance observed during release testing of a small molecule API. The process followed a logical stepwise progression beginning with most probable causes and expanded to more obscure causes that require a deeper examination of the API in question until the undetected impurity in question was finally identified. The discovered impurity was eventually found to be formed from a unique side reaction that led to the formation of API-related oligomer impurities, which had eluded conventional small molecule release testing strategies. Ultimately, the characterization gap was traced back to deficiency in the LC results of the developed API purity methods. More importantly, this gap provides an ideal opportunity to highlight common oversights and pitfalls encountered in early phase pharmaceutical development especially as it relates to the method development of truly representative chromatography methods in the API characterization. The work reflects on the key lessons learned from the highlighted pitfalls that were encountered in this case study and offers strategic insights to guide and to improve the development workflow for drug substance characterization strategies.

Differential role of potential stressors, underlying degradation mechanism, characterization of degradants using LC-MS/MS, and establishment of a stability-indicating analytical method for duvelisib

Duvelisib (DUV) was first approved globally in 2018. An extensive literature search revealed that the differential role of a potential degradation medium in altering the shelf-life of DUV due to its exposure during storage has not been identified till date. Moreover, its degradation impurities and degradation mechanism are not known. In addition, no analytical method has been reported for the quantification of DUV in the presence of its degradation impurities. Therefore, the aim of this study was to identify the impact of different potential degradation media on the stability of DUV, establish the degradation mechanism, and identify its major degradation impurities. The aim was also to establish a stability-indicating analytical method for the quantification of DUV in the presence of its degradation impurities. This study is the first to report the structure of degradation impurities and the step-by-step degradation mechanism of DUV. This information will be useful for the scientific community and manufacturers in optimizing the formulation parameters and/or storage conditions. The validated method can be employed for analysis of stability study and routine quality control samples of newer DUV formulations in pharmaceutical industries. The identified impurities may serve as impurity standards for specifying their limits in the drug after required qualification studies.

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.

Validation of stability-indicating LC method, degradation study, and impact on antioxidant and antifungal activities of Eugenia uniflora leaves extract

The aim of this study is to demonstrate the stability-indicating capacity of an analytical method for Eugenia uniflora, enhance understanding of the stability of myricitrin, and assess the effect of degradation of spray-dried extract (SDE) on antioxidant and antifungal activities. Validation of the stability-indicating method was carried out through a forced degradation study of SDE and standard myricitrin. The antioxidant and antifungal activities of SDE were evaluated both before and after degradation. The quantification method described was found to be both accurate and precise in measuring myricitrin levels in SDE from E. uniflora, with excellent selectivity that confirmed its stability-indicating capability. The forced degradation study revealed that the marker myricitrin is sensitive to hydrolysis, but generally stable under other stress conditions. By contrast, the standard myricitrin displayed greater susceptibility to degradation under forced degradation conditions. Analysis of the antioxidant activity of SDE before and after degradation showed a negative impact in this activity due to degradation, while no significant effect was observed on antifungal activity. The method described can be a valuable tool in the quality control of E. uniflora, and the findings can assist in determining the optimal conditions and storage of products derived from this species.

Stability and compatibility of intraperitoneal antimicrobials in peritoneal dialysate solutions

To optimise antimicrobial administration in patients with peritoneal dialysis (PD)-related peritonitis, healthcare providers need literature-based information to develop patient-centred pharmacotherapeutic plans. Traditional PD solutions promote osmosis using dextrose or icodextrin with a lactate buffer. Newer PD solutions have modified the osmotic vehicle and buffer. Knowledge of antimicrobial compatibility and stability with newer PD solutions will assist with determining the route of antimicrobial administration as compatible and stable solutions could be delivered directly to the peritoneum using intraperitoneal administration. This review updates the compatibility and stability of antimicrobial additives in newer PD solutions for PD-related peritonitis.

Stability-indicating normal-phase HPLC method development for separation and quantitative estimation of S-enantiomer of lacosamide in pharmaceutical drug substance and tablet dosage form

Lacosamide (LA) is an antiepileptic medicine that is used to treat tonic-clonic seizures, partial-onset seizures, mental problems, and pain. A simple, effective, and reliable normal-phase liquid chromatographic technique was developed and validated to separate and estimate the enantiomer of (S-enantiomer) LA in pharmaceutical drug substance and drug product. Normal-phase LC was performed using USP L40 packing material (250 × 4.6 mm, 5 μm) and a mobile phase of n-hexane and ethanol at 1.0 ml min-1 . The detection wavelength, column temperature, and injection volume used were 210 nm, 25°C, and 20 μl, respectively. The enantiomers (LA and S-enantiomer) were completely separated using a minimum resolution of 5.8 and accurately quantified without any interference in a 25-min run time. Accuracy study for stereoselective and enantiomeric purity trials was conducted between 10 and 200%, with recovery values ranging from 99.4 to 103.1% and linear regression values >0.997. The stability-indicating characteristics were assessed using forced degradation tests. The proposed normal-phase HPLC technique is an alternate approach to the official monograph methods (USP and Ph.Eur.) of LA, and it was successfully used in the evaluation of release and stability samples for both tablet dosage forms and pharmaceutical substances.

Chromatographic reversed HPLC and TLC-densitometry methods for simultaneous determination of serdexmethylphenidate and dexmethylphenidate in presence of their degradation products-with computational assessment

Two Chromatographic methods have been established and optimized for simultaneous determination of serdexmethylphenidate (SER.DMP) and dexmethylphenidate (DMP) in the presence of their degradation products. The first method is a reversed phase high performance liquid chromatography with diode array detection (HPLC-DAD). Isocratic separation was carried out on Waters X-bridge Shield RP₁₈ column (150×3.9×5 μm particle size) using a mixture of 5 mM phosphate buffer (pH 5.5): acetonitrile (40:60, v/v) as a mobile phase, flow rate 1 mL/min and detection at 220 nm. The second method is a thin-layer chromatography (TLC)-densitometry method using methanol: chloroform (70:30, v/v) as a mobile phase and UV scanning at 220 nm. In HPLC method, the linearity range of SER.DMP was (2.5-25 μg/mL); with LOD (0.051 μg/mL) and LOQ (0.165 μg/mL) while for DMP was (2.5-25 μg/mL); with LOD and LOQ of (0.098 μg/mL) and (0.186 μg/mL), respectively. For TLC method the sensitivity range of SER.DMP was (5-25 μg/mL), LOD was (0.184 μg/spot), while LOQ was (0.202 μg/ spot) whereas for DMP the sensitivity range was (5-25 μg/mL) with LOD of (0.115 μg/ spot) and LOQ of (0.237 μg/ spot), respectively. SER.DMP was found to be equally labile to acidic and alkaline hydrolysis, whereas DMP was sensitive to acidic hydrolysis only. Both drugs were successfully determined in presence of acidic and basic degradants by the two developed methods (stability indicating assay method). Chromatographic separation of the degradation products was carried out on TLC aluminum silica plates 60 F254, as a stationary phase, using methanol: dichloroethane: acetonitrile (60:20:20 v/v), as a mobile phase. The degradation pathway was confirmed using TLC, IR, ¹H-NMR and mass spectroscopy; moreover, the separation power was correlated to the computational results by applying molecular dynamic simulation. The developed methods were validated according to the International Conference on Harmonization (ICH) guidelines demonstrating good accuracy and precision. They were successfully applied for quantitation of SER.DMP and DMP in pure and capsule forms. The results were statistically compared with those obtained by the reported method in terms of accuracy, precision and robustness, and no significant difference was found.

Rational Design of Topical Semi-Solid Dosage Forms-How Far Are We?

Specific aspects of semi-solid dosage forms for topical application include the nature of the barrier to be overcome, aspects of susceptibility to physical and chemical instability, and a greater influence of sensory perception. Advances in understanding the driving forces of skin penetration as well as the design principles and inner structure of formulations, provide a good basis for the more rational design of such dosage forms, which still often follow more traditional design approaches. This review analyses the opportunities and constraints of rational formulation design approaches in the industrial development of new topical drugs. As the selection of drug candidates with favorable physicochemical properties increases the speed and probability of success, models for drug selection based on theoretical and experimental approaches are discussed. This paper reviews how progress in the scientific understanding of mechanisms and vehicle-influence of skin penetration can be used for rational formulation design. The characterization of semi-solid formulations is discussed with a special focus on modern rheological approaches and analytical methods for investigating and optimizing the chemical stability of active ingredients in consideration of applicable guidelines. In conclusion, the combination of a good understanding of scientific principles combined with early consideration of regulatory requirements for product quality are enablers for the successful development of innovative and robust semi-solid formulations for topical application.

Application of design space and quality by design methodologies combined with ultra high-performance liquid chromatography for the optimization of the sample preparation of complex pharmaceutical dosage forms

Accurate and precise analytical measurements play a significant role in assessments and decisions that are made throughout the drug development process. Developing a robust and reliable sample preparation is essential for drug product formulations to generate consistent results guaranteeing the product quality. However, due to the complex nature of the different pharmaceutical formulations with diverse excipients, developing robust sample preparation methods can be challenging and time consuming. Ensuring sample extraction robustness of pharmaceutical dosage forms becomes increasingly important with the potential impact to patient safety, product efficacy, and business efficiency. In this work we demonstrate and evaluate potential application of Quality by Design (QbD) principles to develop and optimize a robust sample preparation method in combination with the chromatographic analytical technique for a solid pharmaceutical dosage form. Practicability and utility of a QbD approach in optimization of sample preparation of this drug product are demonstrated as the active pharmaceutical ingredient (API) used in the drug product is proven to be highly sensitive for hydrolysis during analysis. Finally, the ultra-high-performance liquid chromatography method with UV detection that was applied during the design of experiments (DoE) was validated as per regulatory requirements. This systematic approach in analytics could provide guidance for the pharmaceutical industry in the development of robust sample preparation methods for different pharmaceutical dosage forms thus significantly reduce risks associated with the method transfers at clinical and commercial manufacturing sites.

Optimization of High-Performance Liquid Chromatographic Method Using Central Composite Design for the Simultaneous Estimation of Ciprofloxacin and Loteprednol

A simple, rapid, precise and accurate stability indicating high-performance liquid chromatographic (HPLC) method was developed for simultaneous quantification of Ciprofloxacin (CIP) and Loteprednol (LOT) along with their forced degradation products using central composite design (CCD) approach. CCD was prepared with three independent variables in a gradient HPLC method. In gradient program (GP) the ratio of phosphate buffer in the mobile phase was 70%, 75%, 80%, 85% and 90%, the pH of phosphate buffer was 2.6, 2.8, 3.0, 3.2 and 3.4, flow rate was 0.8, 0.9, 1.0, 1.1 and 1.2 mL/min. Resolution, tailing factor (CIP) and tailing factor (LOT) were selected as response factor. The effective separation of LOT and CIP was achieved on Phenomenex EVO-C18 column (4.6 mm × 250 mm × 5 μm particle size) opting gradient mode of elution. The mobile phase composed of 10 mM Phosphate buffer pH 3.2 with ortho-phosphoric acid and the organic phase composed of mixture of acetonitrile and methanol in 50:50% v/v with flow rate of 1 mL/min and diode array detection at 258 nm. The optimized variables found were flow rate of 1.0 mL/min, ratio of phosphate buffer in GP 80% at pH 3.0. The method was validated as per ICH guidelines and applied for analysis of stability samples.

Development of a rapid and validated stability-indicating UPLC-PDA method for concurrent quantification of impurity profiling and an assay of ipratropium bromide and salbutamol sulfate in inhalation dosage form

The objective of the proposed work was to develop a rapid and new reverse phase ultra-performance liquid chromatographic (RP-UPLC) method for the simultaneous quantification of related impurities of ipratropium bromide and salbutamol sulfate in the combined inhalation dosage form. Herein, the chromatographic separation was achieved on Acquity BEH C18 (100mm×2.1mm, 1.7μm) column by following gradient elution of solvent A as 2mM potassium dihydrogen phosphate with 0.025% of 1-pentane sulphonic acid sodium salt (pH 3.0 buffer) and solvent B as pH 3.0 buffer, acetonitrile and methanol in the ratio of (32:50:18, v/v/v) at a flow rate of 0.3mL/min. The samples were detected and quantified at 220nm. To prove the stability-indicating potential of the method, forced degradation studies were performed using acidic, basic, oxidative, thermal, and photolytic conditions. After sufficient exposure, the resultant solutions were injected and found that all degradants and impurities formed during stress studies were well separated from each other and from the main peak compounds. The performance of the method was validated according to the present ICH Q2 (R1) guidelines. The method has good linearity (r≥0.999) and consistent recoveries were obtained with a range of 91.3-108.8% for all compounds. The % RSD obtained for the precision experiments was less than 5% and also there is a good sensitivity (LOQ≤0.5μg/mL) for all compounds. The intended method proved its applicability and that it can be beneficial to pharmaceutical industries for quick quantification of related impurities and assay in quality control department for analysis of ipratropium bromide and salbutamol sulfate inhalation dosage form.

MassChemSite for In-Depth Forced Degradation Analysis of PARP Inhibitors Olaparib, Rucaparib, and Niraparib

Drugs must satisfy several protocols and tests before being approved for the market. Among them, forced degradation studies aim to evaluate drug stability under stressful conditions in order to predict the formation of harmful degradation products (DPs). Recent advances in LC-MS instrumentation have facilitated the structure elucidation of degradants, although a comprehensive data analysis still represents a bottle-neck due to the massive amount of data that can be easily generated. MassChemSite has been recently described as a promising informatics solution for LC-MS/MS and UV data analysis of forced degradation experiments and for the automated structural identification of DPs. Here, we applied MassChemSite to investigate the forced degradation of three poly(ADP-ribose) polymerase inhibitors (olaparib, rucaparib, and niraparib) under basic, acidic, neutral, and oxidative stress conditions. Samples were analyzed by UHPLC with online DAD coupled to high-resolution mass spectrometry. The kinetic evolution of the reactions and the influence of solvent on the degradation process were also assessed. Our investigation confirmed the formation of three DPs of olaparib and the wide degradation of the drug under the basic condition. Intriguingly, base-catalyzed hydrolysis of olaparib was greater when the content of aprotic-dipolar solvent in the mixture decreased. For the other two compounds, whose stability has been much less studied previously, six new degradants of rucaparib were identified under oxidative degradation, while niraparib emerged as stable under all stress conditions tested.

TLC–Densitometric Analysis of Selected 5-Nitroimidazoles

Metronidazole, ornidazole, tinidazole, and secnidazole are 5-nitroimidazoles. The purpose of this work was to propose a new economical TLC–densitometric method to evaluate the chemical stability of metronidazole, secnidazole, ornidazole, and tinidazole under stress conditions. A forced degradation study was performed on silica gel and aqueous solutions at various pH values; the metronidazole, secnidazole, ornidazole, and tinidazole solutions were prepared in saline and in hydrogen peroxide, respectively. The samples of the 5-nitroimidazoles were heated. TLC analyses were performed on silica gel 60F254 using chloroform–methanol (9:1, v/v) as the mobile phase. As the TLC–densitometric method can effectively separate the metronidazole, secnidazole, ornidazole, and tinidazole from their degradation products which formed as a result of the stress studies, it is considered to can be a good alternative and important tool in the routine quality control and stability testing of metronidazole, secnidazole, ornidazole, and tinidazole in pharmaceutical formulations. The results indicate that the proposed TLC–densitometric method is cost-effective, rapid, specific, accurate, and precise; the TLC–densitometric method also realizes the criterion of the linearity. A major advantage of the proposed method is its low cost and ability to analyze the 5-nitroimidazole which was investigated and all its degradation products simultaneously.

Simultaneous determination of emtricitabine, tenofovir alafenamide fumarate and dolutegravir sodium by validated stability-indicating RP-HPLC-DAD method

OBJECTIVE

The purpose of this research was to develop and validate a stability-indicating RP-HPLC technique for simultaneous quantification of Emtricitabine (EMT), Tenofovir Alafenamide Fumarate (TEN), and Dolutegravir Sodium (DOL) in bulk and in their combined formulation.

MATERIAL AND METHODS

The developed approach was done on Exterra C18 column (150×4.6mm, 5μm) and Methanol and Buffer (comprising 0.1 (v/v) of Triethylamine and o-phosphoric acid in water, pH 2.6) as mobile phase in the proportion of 75:25 (v/v), eluted at 1mL/min. The analytes were quantified using DAD detector at 265nm.

RESULTS

The approach was validated in accordance with the ICH guidelines. Linearity, precision, accuracy, specificity, Limit of Detection (LOD), Limit of Quantitation (LOQ), and robustness were used to validate the proposed method. Linear response was found in the range of 500-1500μg/mL for EMT, 62.5-187.5μg/mL for TEN and 125-375μg/mL for DOL. The LOD values of EMT, TEN and DOL were found 91.78μg/mL, 10.47μg/mL and 19.28μg/mL correspondingly. The LOQ values of EMT, TEN and DOL were found and 278.11μg/mL, 31.74μg/mL and 58.42μg/mL correspondingly. The assay outcomes for all drugs were observed between 99.11-100.84%. To access the method's stability indicating capabilities, the drugs were exposed to various environmental (acid, alkaline, neutral, oxidative, photolytic and thermal) conditions.

CONCLUSION

The established approach was considered to be accurate, linear, precise, specific, robust and it can be utilized to analyse the drugs mentioned in its tablet.

Development and validation of a stability-indicating high performance liquid chromatographic assay for determination of cariprazine in bulk form and in drug product

The aim of the present study is to develop a stability indicating high performance liquid chromatographic method for the determination of cariprazine in bulk substance and in drug product. The chromatographic separation was carried out using a Phenomenex Kinetex® C18 column (5μm, 250×4.6mm) and a mobile phase consisting of acetonitrile-potassium dihydrogen orthophosphate buffer (pH 4; 50mM) (30:70, v/v), at a flow rate of 1mlmin -1 and UV detection at 248nm. The column was maintained at 25°C and an injection volume of 20μL was used. Stress testing of cariprazine bulk substance and drug product was performed according to the International Conference on Harmonization (ICH) Q1A (R2) guideline. Various stress conditions were tested including acidic, alkaline and neutral hydrolysis, humidity, oxidation, dry heat and photolysis. A total of three degradation products (DPs) were formed. Among them two DPs were successfully characterized with the liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis.

Novel Eco-Friendly Stability Indicating Capillary Zone Electrophoresis Method for Determination of Aripiprazole in Tablet Dosage form: DoE Directed Optimization, Development and Method Validation

In this work, a novel environment-friendly stability indicating capillary zone electrophoresis (CZE) method has been developed and validated for assaying the aripiprazole (ARP) in tablet dosage form. The separation of ARP from its degradation products and internal standard was achieved using a fused silica capillary column (30.2 cm x 75 μm ID), a background electrolyte containing 6 mmol L^-1 ammonium formate buffer (pH 3) with 5% methanol under a potential of 15 kV and detection at 214 nm. The stability indicating ability of the method was investigated by analyzing ARP after being subjected to acidic, alkaline, thermal, photolytic, and oxidative stress conditions, according to ICH guidelines. Design of experiments was used during forced degradation and method optimization. Oxidation was the main degradation pathway among those evaluated. The drug was separated from its oxidative degradation products in less than 4 min. CZE method was linear between 60 - 140 μg mL^-1, R² = 0.9980, precise (intra-day 0.88% and inter-day 1.30%). The average recovery was 100.93 ± 0.77%. This is the first method in the literature for quantification of ARP in the presence of its related degradation products with high separation efficiency, low operation cost and minimum solvent consumption. This method could be helpful in the routine quality control analysis in the pharmaceutical industries with least harmful effect on the environment. CZE is considered an eco-friendly alternative of conventionally HPLC methods.

Mini Review on Forced Degradation Studies on Anti-Epileptic Drugs and Beyond

In this review on the forced degradation studies on anti-epileptic drugs and the development of validated stability-indicating assay methods for drug substances and products at a condition more severe than accelerated condition (i.e. 40 ± 2°C, 75 ± 5% relative humidity), the drug substance and drug product undergo degradation is known as forced or stress degradation. To know about the impurities developed during the storage of drug products in various environmental conditions. The limit of degradation allowable is 5-20%. More than 20% of degradation is abnormal and must be investigated. Any regulatory guidelines do not mention the pH conditions for acid or base hydrolysis, the temperature for thermal degradation or the concentration of the oxidation agent. Only International Conference on Harmonization (ICH) guidelines Q1B photostability stability and states that light sources must be a combination of UV and visible light. The shortcomings of mentioned techniques with appreciation to regulatory necessities are highlighted. A systematic method for the forced degradation studies on anti-epileptic drugs such as "Topiramate, Vigabatrin, Lacosamide, Tiagabine, Levetiracetam and Zonisamide" is discussed. This review helps researchers to get an idea about stability-indicating methods of development and validation for newer antiepileptic drugs and the characteristics of drug products that degrade under specific degradation conditions.

High Performance Liquid Chromatography (HPLC) with Fluorescence Detection for Quantification of Steroids in Clinical, Pharmaceutical, and Environmental Samples: A Review

Steroids are compounds widely available in nature and synthesized for therapeutic and medical purposes. Although several analytical techniques are available for the quantification of steroids, their analysis is challenging due to their low levels and complex matrices of the samples. The efficiency and quick separation of the HPLC combined with the sensitivity, selectivity, simplicity, and cost-efficiency of fluorescence, make HPLC coupled to fluorescence detection (HPLC-FLD) an ideal tool for routine measurement and detection of steroids. In this review, we covered HPLC-FLD methods reported in the literature for the steroids quantification in clinical, pharmaceutical, and environmental applications, focusing on the various approaches of fluorescent derivatization. The aspects related to analytical methodology including sample preparation, derivatization reagents, and chromatographic conditions will be discussed.

Oxidation of Drugs during Drug Product Development: Problems and Solutions

Oxidation is the second most common degradation pathway for pharmaceuticals, after hydrolysis. However, in contrast to hydrolysis, oxidation is mechanistically more complex and produces a wider range of degradation products; oxidation is thus harder to control. The propensity of a drug towards oxidation is established during forced degradation studies. However, a more realistic insight into degradation in the solid state can be achieved with accelerated studies of mixtures of drugs and excipients, as the excipients are the most common sources of impurities that have the potential to initiate oxidation of a solid drug product. Based on the results of these studies, critical parameters can be identified and appropriate measures can be taken to avoid the problems that oxidation poses to the quality of a drug product. This article reviews the most common types of oxidation mechanisms, possible sources of reactive oxygen species, and how to minimize the oxidation of a solid drug product based on a well-planned accelerated study.

LC-HRMS studies on ruxolitinib degradation: a comprehensive approach during drug development

Ruxolitinib, a kinase inhibitor, was subjected to stress studies as described in the ICH Q1A(R2) guidelines. Solution state hydrolytic and solid state oxidative and thermal stress studies were carried out to understand its degradation behaviour. The drug showed significant instability in the hydrolytic condition in comparison with other conditions. HPLC and UHPLC methods were developed for the separation of the drug and its hydrolytic degradation products. Mass fragmentation pathway of the drug was established as the first step of the LC-MS characterization of the degradation products. MS/MS analysis of the drug and MS³ of selected fragments were achieved through QTOF and QTRAP by varying the collision energy and performing an H/D exchange. LC-MS/MS QTOF studies were subsequently carried out on stress samples and the structures of the degradation products were identified through comparison of the drug fragmentation pathways. The four hydrolytic products viz. 4-(1H-pyrazol-4-yl)-7H-pyrrolo[2,3-d]pyrimidine, 3-(4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1H-pyrazol-1-yl)-3-cyclopentylpropanoic acid, 3-(4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1H-pyrazol-1-yl)-3-cyclopentylpropanamide, and 3-(4-(6-amino-5-formylpyrimidin-4-yl)-1H-pyrazol-1-yl)-3-cyclopentylpropanenitrile were formed under acidic and basic conditions. The degradation pathway was delineated through a mechanistic explanation. The in silico tools preADMET and Protox-II predictor were used to compare the toxicity of the impurities with respect to the drug.

Pharmacokinetic, Metabolomic, and Stability Assessment of Ganoderic Acid H Based Triterpenoid Enriched Fraction of Ganoderma lucidum P. Karst

Ganoderma lucidum P. karst is an edible fungus that is used in traditional medicine and contains triterpenoids as the major phytoconstituents. Ganoderic acids are the most abundant triterpenoids that showed pharmacological activity. As Indian varieties contain ganoderic acid H (GA-H), we aimed to prepare GA-H-based triterpenoid enriched fraction (TEF) and evaluated its pharmacokinetics, metabolomics, and stability analysis. A high-performance liquid chromatography (HPLC) method was developed to quantify GA-H in TEF and rat plasma. Based on GA-H content, a stability assessment and pharmacokinetic study of TEF were also performed. After its oral administration to rats, TEF’s the metabolic pattern recognition was performed through ultra-performance liquid chromatography mass spectroscopy (UPLC–MS). The developed HPLC method was found to be simple, sensitive, precise (<15%), and accurate (>90% recovery) for the quantification of GA-H. Pharmacokinetic analysis showed that GA-H reached its maximum plasma concentration (C_max 2509.9 ng/mL) within two hours and sustained quantifiable amount up to 12 h with a low elimination rate (K_el) 0.05 L/h. TEF contained ten bioavailable constituents. The prepared TEF was found to be stable for up to one year at room temperature. The prepared TEF, enriched with ganoderic acid, is stable, contains bioavailable constituents, and can be explored as phytopharmaceuticals for different pharmacological properties. Highlights: (1). Preparation of triterpenoid enriched fraction (TEF) from Ganoderma lucidum. (2). Major triterpenoid in TEF is ganoderic acid H (GA-H). (3). TEF contains several bioavailable phytoconstituents. (4). TEF (considering only GA-H) is stable for up to one year at room temperature. (5). GA-H is rapidly absorbed and has high systemic exposure.

Separation and Characterization of the Related Substances of Bedaquiline Fumarate Using HPLC and Spectral Methods

The study focuses on isolating and characterizing the potential degradation products (DPs) and impurities of Bedaquiline fumarate in bulk drug form. A stability-indicating related substance method was developed and validated using high-performance liquid chromatography. Agilent Poroshell 120EC- C18 (150 mm × 4.6 mm, 2.7 μm) column showed an optimum separation of 10 analytes. The mobile phase contained 0.05% trifluoroacetic acid, acetonitrile and methanol in a time gradient mode. Bedaquiline fumarate was susceptible to acid hydrolysis, oxidation, base hydrolysis and showed three potential DPs, including DP-1, DP-2 and Impurity-8. Degradation products, DP-1 and DP-2, were isolated and characterized by ESI-MS, 1H, NMR and 13C NMR spectroscopy. The developed method was validated according to ICH tripartite guidelines and showed adequate specificity, accuracy and linearity. The limit of detection and limit of quantitation were 0.05 and 0.15 μg/mL, respectively.

UHPLC-DAD Method Development and Validation: Degradation Kinetic, Stress Studies of Farnesol and Characterization of Degradation Products Using LC-QTOF-ESI-MS with in silico Pharmacokinetics and Toxicity Predictions

Farnesol (FAR) is a sesquiterpene molecule with high lipophilicity that has antibacterial and other pharmacological properties along with broad nutritional values with high commercial values. Although having potential, FAR stability behavior and degradation kinetics are not available in the literature. Hence, it is very essential to develop a simple, rapid, accurate, precise, robust, cheap UHPLC-DAD method for FAR. It was also proposed to study mechanistic insights into FAR under different degradation conditions. Therefore, we hypothesized to do systematic stability studies along with degradation kinetic and accelerated stability studies. The developed method was validated. FAR was studied for stress studies, degradation kinetics and ADMET prediction of degradants. Degradation products were characterized using LC-QTOF-ESI-MS. Developed method consists of an isocratic mobile phase with a wavelength of 215 nm. The percent recoveries for FAR were observed within the acceptance limit of 98-102%. The eight major degradation products were formed during stress studies. FAR follows first-order degradation kinetics. FAR and all degradants were found to have more than 75% good human oral absorption, and are non-toxic. FAR UHPLC-DAD method was developed, validated and performed stability studies to know the possible degradation pattern along with degradation kinetic studies.

A simple isocratic LC method for quantification of trace-level inorganic degradation impurities (ferricyanide, ferrocyanide, nitrite, and nitrate) in sodium nitroprusside injection and robustness by quality using design approach

This study developed and validated a trace-level quantification inorganic impurities method using reversed-phase HPLC and performed the robustness check using quality-by-design approach by varying the multiple factors simultaneously. This method is economical and simple and exhibits its stability-indicating nature [for the determination of ferrocyanide ([Fe(CN)₆]^4- ), ferricyanide ([Fe(CN)₆ ]^3- ), nitrate (NO₃ ^- ), and nitrite (NO₂ ^- )] in sodium nitroprusside (SNP) drug substance and liquid dosage form. Chromatographic separation was achieved using a USP L43 column (ACE PFP, 150 × 4.6 mm, 3 μm) with a simple isocratic elution. The buffer consists of potassium dihydrogen phosphate (50 mM), tetrabutylammonium hydrogen sulfate (9 mM), and tetrabutylammonium hydroxide (25 mM). The buffer pH was adjusted to 7.2 with tetrabutylammonium hydroxide. The mobile phase was mixed with the buffer and acetonitrile (68:32 v/v). The flow rate was 0.8 mL/min, column temperature was maintained at 30°C, and injection volume was 5.0 μL. The SNP impurities were monitored at 225 nm using a UV detector. Further, the method was validated per the International Council for Harmonisation (ICH) guidelines, and forced degradation studies were carried out under different stress conditions. The detector responses were plotted against concentrations, and correlation was linear (r > 0.999) over the range of 0.8-7.5 μg/mL for ferricyanide; 1.0-37.5 μg/mL for SNP; and 0.2-7.5 μg/mL for ferrocyanide, nitrite, and nitrate. The method repeatability was established for all the impurities with relative standard deviation (%), and the results were found to be less than 2.0.

A Tribute to Professor Saranjit Singh - A Critical Thinker, Innovator, Mentor, and Educator

This commentary presents contributions and accomplishments of Professor Saranjit Singh, National Institute of Pharmaceutical Education and Research (NIPER), SAS Nagar, India, to pharmaceutical research and education. Prof. Singh completed his successful tenure in October 2021. Over his 40+ years of illustrious academic career, he trained 147 Masters and 15 PhD students in the fields of drug stability testing, degradation chemistry, impurity and metabolite characterization, and advanced analytical technologies. He has published ∼250 research articles, reviews, editorials, patent, book, and book chapters, and received numerous awards, including the Professor M.L. Khorana Memorial Lecture Award from the Indian Pharmaceutical Association (IPA) and the Outstanding Analyst and Eminent Analyst awards from the Indian Drug Manufacturers' Association (IDMA). This commentary highlights Prof. Singh's inspiring personal and renowned professional journey, including early life, education, career, accomplishments, as well as his services to academia, industry, and regulatory. By sharing the contributions and accomplishments of Prof. Singh, we strongly believe that his story will inspire the next generation of scientists to continue his legacy to advance the field.

A novel stability-indicating method for known and unknown impurities profiling for diltiazem hydrochloride pharmaceutical dosage form (tablets)

Background

A novel gradient, high-sensitive and specific stability-indicating reverse-phase HPLC method was developed and validated for quantitative purpose of known, unknown and degradant impurities profiling for diltiazem hydrochloride tablets. The impurities were separated on the Zorbax RX C8 column (150 mm × 4.6 mm, 5 μm) with mobile phase-A consisting of a mixture of 0.05 M sodium dihydrogen phosphate monohydrate buffer pH 3.0 and methanol in the ratio 800:200v/v and mobile phase-B consisting of acetonitrile with a flow rate of 1.0 mL min−1. The column compartment was maintained at 35 °C, and the detection wavelength was 240 nm. Diltiazem hydrochloride, its known impurities and unknown impurities have been well resolved from each other.

Results

The linearity of the method has been demonstrated across the concentration range of 0.18 to 5.65 µg mL−1 for EP impurity-F with correlation coefficient R2 greater than 0.99. Recovery of method was proved from LOQ to 150% for known and unknown impurities with respect to test concentration and found in between 80 and 120%. Forced degradation study and specificity experiment results with mass balance proved the stability-indicating nature of the method and separated all known, unknown impurities and degradants from each other as well as from main drug component (diltiazem hydrochloride). The mass balance for stress study was found in between 95 and 105%.

Conclusion

Newly developed analytical method was validated as per ICH Q2 (R1) guidelines “Validation of analytical procedure” and found linear, accurate, specific, robust and precise in the established working range.

Development and Validation of a New Storage Procedure to Extend the In-Use Stability of Azacitidine in Pharmaceutical Formulations

Stability studies performed by the pharmaceutical industry are principally designed to fulfill licensing requirements. Thus, post-dilution or post-reconstitution stability data are frequently limited to 24 h only for bacteriological reasons, regardless of the true physicochemical stability which could, in many cases, be longer. In practice, the pharmacy-based centralized preparation may require preparation in advance for administration, for example, on weekends, holidays, or in general when pharmacies may be closed. We report an innovative strategy for storing resuspended solutions of azacitidine, a well-known chemotherapic agent, for which the manufacturer lists maximum stability of 22 h. By placing the syringe with the azacitidine reconstituted suspension between two refrigerant gel packs and storing it at 4 °C, we found that the concentration of azacitidine remained above 98% of the initial concentration for 48 h, and no change in color nor the physicochemical properties of the suspension were observed throughout the study period. The physicochemical and microbiological properties were evaluated by HPLC–UV and UHPLC-HRMS analysis, FTIR spectroscopy, pH determination, visual and subvisual examination, and sterility assay. The HPLC-UV method used for evaluating the chemical stability of azacitidine was validated according to ICH. Precise control of storage temperature was obtained by a digital data logger. Our study indicates that by changing the storage procedure of azacitidine reconstituted suspension, the usage window of the drug can be significantly extended to a time frame that better copes with its use in the clinical environment.

A New, Rapid and Simple RP-HPLC Method for Stability Quantification of a Protease Inhibitor in Tablets

Fosamprenavir calcium is a protease inhibitor widely used in the treatment and prevention of human immunodeficiency virus and acquired immunodeficiency syndrome. This protease inhibitor serves as a prodrug of amprenavir, offering better oral bioavailability. Although this drug was approved by the FDA in 2003, there are few methods established for quantifying the stability for quality control analysis of fosamprenavir-coated tablets. The purpose of the study was to develop and validate a method for determining the stability of fosamprenavir-coated tablets (Telzir®) that may be applied by any quality control laboratory. Chromatographic separation was performed using a Vertical RP-18 column programmed to run a gradient elution with sodium acetate buffer and acetonitrile. Flow rate was 1.2 mL min-1 for a total run time of 15 min. Ultraviolet detection was set at 264 nm and the use of a photodiode array detector in scan mode allowed selectivity confirmation by peak purity evaluation. The analyte peak was found to be adequately separated from degradation products generated during forced degradation studies. Thus, the proposed method was found to accurately indicate stability and was sufficient for routine quantitative analysis of fosamprenavir in coated tablets without interference from major degradation products and excipients.

A Stability-Indicating Ultra Performance Liquid Chromato-Graphic (UPLC) Method for the Determination of a Mycophenolic Acid-Curcumin Conjugate and Its Applications to Chemical Kinetic Studies

A simple, precise, and accurate reversed-phase ultra-performance liquid chromatographic (UPLC) method was developed and validated for the determination of a mycophenolic acid-curcumin (MPA-CUR) conjugate in buffer solutions. Chromatographic separation was performed on a C18 column (2.1 × 50 mm id, 1.7 µm) with a gradient elution system of water and acetonitrile, each containing 0.1% formic acid, at a flow rate of 0.6 mL/min. The column temperature was controlled at 33 °C. The compounds were detected simultaneously at the maximum wavelengths of mycophenolic acid (MPA), 254 nm, and curcumin (CUR), or MPA-CUR, at 420 nm. The developed method was validated according to the ICH Q2(R1) guidelines. The linear calibration curves of the assay ranged from 0.10 to 25 μg/mL (r² ≥ 0.995, 1/x² weighting factor), with a limit of detection and a limit of quantitation of 0.04 and 0.10 μg/mL, respectively. The accuracy and precision of the developed method were 98.4-101.6%, with %CV < 2.53%. The main impurities from the specificity test were found to be MPA and CUR. Other validation parameters, including robustness and solution stability, were acceptable under the validation criteria. Forced degradation studies were conducted under hydrolytic (acidic and alkaline), oxidative, thermal, and photolytic stress conditions. MPA-CUR was well separated from MPA, CUR, and other unknown degradation products. The validated method was successfully applied in chemical kinetic studies of MPA-CUR in different buffer solutions.

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.

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.

Characterization of degradation products of celiprolol hydrochloride using hyphenated mass and NMR techniques

Stress degradation studies were carried out on celiprolol hydrochloride under the ICH prescribed hydrolysis (acidic, basic and neutral), photolytic, oxidative and thermal conditions. Maximum degradation was observed upon hydrolysis, especially in the basic condition. In oxidative condition, the drug degraded only upon severe exposure to H₂O₂, but it remained stable when challenged with AIBN. It also degraded significantly under photolytic conditions. However, the drug was stable to thermal stress. A total of seven degradation products were formed, whose separation was successfully achieved on an Inertsil ODS-3V C-18 HPLC column employing a gradient mobile phase. A comprehensive mass fragmentation pattern of the drug was initially established through the support of high resolution mass spectrometry (HR-MS), multi-stage tandem mass spectrometry (MSⁿ) and on-line H/D exchange MS data. The same approach was then extended to characterization of the degradation products. Additionally, two degradation products were isolated and subjected to 1D/2D NMR studies for their structural confirmation. One of the degradation products showed instability during isolation, therefore, it was subjected to LC-NMR studies for its structural confirmation.

Exploitation of flow-based procedures for reagentless hydrochlorothiazide determination and accelerated degradation studies of pharmaceutical preparations

Drug quality assessment and stress testing are important to ensure both treatment efficacy and patient safety. High performance liquid chromatography may be considered a standard technique for pharmaceutical analysis, showing good precision and accuracy, but it also involves relatively high cost and low analytical frequency. Flow injection analysis presents high sample throughput, lower cost and might be used for selective drug analysis with an appropriate assay and/or detector. In this paper, for the first time, photoreactions promoted by UV radiation were employed for reagentless spectrophotometric determination of hydrochlorothiazide. Optimized parameters led to a linear range of 50 to 500 mg L^-1, estimated limit of detection of 3.0 mg L^-1 and 24 determinations per hour. The use of diluted NaOH solution as a carrier allowed solubilization of hydrochlorothiazide and analysis without organic solvents. The presence of the most common excipients was evaluated and no significant interferences were observed. The results from the analysis of samples by the proposed and by the reference procedures demonstrated accuracy and matching results. The proposed in-line photolysis of the pharmaceutical, performed in 5 min, is a promising alternative to the conventional hydrolytic forced degradation, which requires elevated temperature and prolonged time period. To evaluate the degree of photoconversion, a capillary zone electrophoresis method was developed, which performed well for separations manifesting good analytical frequency and reduced amount of waste. The combination of in-line photodegradation followed by separation by capillary electrophoresis is a promising approach for the stress test of hydrochlorothiazide in pharmaceutical formulations.

Insights into flibanserin oxidative stress degradation pathway: in silico – in vitro toxicity assessment of its degradates

Characterization of the degradation products of pharmaceutical drugs is essential to assess their safety.