Nitrosamine Contamination in Pharmaceuticals: Threat, Impact, and Control

An Agile and Accurate Approach for N-Nitrosamines Detection and Quantification in Medicines by DART-MS

N-nitrosamines (NAs) are prevalent mutagenic impurities in various consumer products. Their discovery in valsartan-containing medicines in 2018 prompted global regulatory agencies to set guidelines on their presence and permissible levels in pharmaceuticals. In order to determine the NAs content in medicines, efficient and sensitive analytical methods have been developed based on mass spectrometry techniques. Direct analysis in real time-mass spectrometry (DART-MS) has emerged as a prominent ambient ionization technique for pharmaceutical analysis due to its high-throughput capability, simplicity, and minimal sample preparation requirements. Thus, in this study DART-MS was evaluated for the screening and quantification of NAs in medicines. DART-MS analyses were conducted in positive ion mode, for both direct tablet analysis and solution analysis. The analytical performance was evaluated regarding linearity, precision, accuracy, limits of detection, and quantification. The DART-MS proved to be suitable for the determination of NAs in medicines, whether through direct tablet analysis or solution analysis. The analytical performance demonstrated linearity in the range from 1.00 to 200.00 ng mL-1, limits of quantification about 1.00 ng mL-1, precision and accuracy lower than 15%, and no significant matrix effect for six drug-related NAs. In conclusion, the DART-MS technique demonstrated to be an alternative method to determine NAs in medicines, aligning with the principles of green chemistry.

Impurities in Active Pharmaceutical Ingredients and Drug Products: A Critical Review

The presence of impurities in active pharmaceutical ingredients (APIs) and drug products represents a risk to patients' health. Such substances are related to diverse side effects and may have mutagenic potential. That's why it is necessary to establish acceptable limits for these by-products, to minimize the risk associated with medicinal therapy. This work focused on presenting a critical review of relevant points related to the presence of impurities in pharmaceuticals. The main legislation and guidelines from the FDA, EMA, ICH, and Pharmacopeias about the subject were evaluated, and recent articles related to the topic were searched in Scopus, ScienceDirect, PubMed, and Web of Science from 2013 to 2023. Additionally, the analytical techniques used for quantifying impurities were discussed, along with relevant tests for assessing the toxicological and mutagenic risks of these by-products. Recent legislation, including ICH Q3A (R2), ICH Q3B (R2), ICH M7 (R2), ICH Q3D (R2), ICH Q3C (R9), ICH Q3E, ICH Q6A, ICH M3 (R2), as well as FDA and EMA guidelines, highlights a comprehensive and effective framework for controlling impurities in pharmaceuticals. Despite this, there remains a lack of harmonization and standardized procedures across different regions. From the review of scientific literature, we observed that advancements in analytical techniques have significantly improved the sensitivity and selectivity in detecting impurities and degradation products. This underscores the ongoing commitment of health agencies and the pharmaceutical industry to ensure the safety and efficacy of medicinal products.

N-nitrosamine impurity risk assessment in pharmaceuticals: Utilizing In vivo mutation relative potency comparison to establish an acceptable intake for NTTP

The finding of N-nitrosodiethylamine (NDEA) and N-nitrosodimethylamine (NDMA) in marketed drugs has led to implementation of risk assessment processes intended to limit exposures to the entire class of N-nitrosamines. A critical component of the risk assessment process is establishing exposure limits that are protective of human health. One approach to establishing exposure limits for novel N-nitrosamines is to conduct an in vivo transgenic rodent (TGR) mutation study. Existing regulatory guidance on N-nitrosamines provides decision making criteria based on interpreting in vivo TGR mutation studies as an overall positive or negative. However, point of departure metrics, such as benchmark dose (BMD), can be used to define potency and provide an opportunity to establish relevant exposure limits. This can be achieved through relative potency comparison of novel N-nitrosamines with model N-nitrosamines possessing robust in vivo mutagenicity and carcinogenicity data. The current work adds to the dataset of model N-nitrosamines by providing in vivo TGR mutation data for N-nitrosopiperidine (NPIP). In vivo TGR mutation data was also generated for a novel N-nitrosamine impurity identified in sitagliptin-containing products, 7-nitroso-3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo-[4,3-a]pyrazine (NTTP). Using the relative potency comparison approach, we have demonstrated the safety of NTTP exposures at or above levels of 1500 ng/day.

Assessing the genotoxicity of N-nitrosodiethylamine with three in vivo endpoints in male Big Blue® transgenic and wild-type C57BL/6N mice

The detection of N-nitrosamines in drug products has raised global regulatory interest in recent years due to the carcinogenic potential of some nitrosamines in animals and a need to identify a testing strategy has emerged. Ideally, methods used would allow for the use of quantitative analysis of dose-response data from in vivo genotoxicity assays to determine a compound-specific acceptable intake for novel nitrosamines without sufficient carcinogenicity data. In a previous study we compared the dose-response relationships of N-nitrosodiethylamine (NDEA) in three in vivo genotoxicity endpoints in rats. Here we report a comparison of NDEA's genotoxicity profile in mice. Big Blue® mice were administered NDEA at doses of 0.001, 0.01, 0.1, 1 and 3 mg/kg/day by oral gavage for 28 days followed by 3 days of expression. Statistically significant increases in the NDEA induced mutations were detected by both the transgenic rodent mutation assay (TGR) using the cII endpoint and by duplex sequencing in the liver but not bone marrow of mice. In addition, administration of NDEA for two consecutive days in male C57BL/6N mice caused elevated DNA damage levels in the liver as measured by % tail DNA in comet assay. The benchmark dose (BMD) analysis shows a BMDL50 of 0.03, 0.04 and 0.72 mg/kg/day for TGR, duplex sequencing and comet endpoints, respectively. Overall, this study demonstrated a similar genotoxicity profile of NDEA between mice and rats and provides a reference that can be used to compare the potential potency of other novel nitrosamines for the induction of gene mutations.

The continuing challenge of drug recalls: Insights from a ten-year FDA data analysis

In this study we analyzed drug recall data from the U.S. Food and Drug Administration (FDA) over the period 2012-2023. We identified trends in the number of recalls initiated annually and their underlying causes. On average, 330 drug recalls are initiated each year, showing an overall increasing trend. The average duration of a recall, from initiation to termination date, was 1.3 years and each recall involved on average 400 000 product units, implying considerable resource demands and consequences for all stakeholders. The most frequent cause of these recalls was found to be impurities and contaminants (37 %), followed by control (28 %) and labeling/packaging (19 %) issues. Recalls of medicines causing serious health problems or death (class I), accounted for 14 % of the recall events. Continuous evaluation of recalls is expected to reduce their number, mitigate their impact on the healthcare system and improve drug safety.

Risk-Based Approach for Defining Retest Dates for Active Pharmaceutical Ingredients and Excipients

Drug substances and excipients must be stored in recommended storage conditions and should comply with their specifications during the retest period for their use in the manufacture of drug products. The ICH (International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use) and WHO (World Health Organization) regulatory guidelines mandate that after the retest period, the drug substances must be retested for compliance with the specification and then used immediately in the manufacture of the finished product. Although these substances can be retested multiple times, an emphasis is placed on immediate use following a retest and compliance with standards. The phrase "used immediately" is ambiguous and is left for interpretation. In this article, we will look at the various processes that must be completed to determine the retest date. In addition, we present a risk-based method for establishing retest dates and the time during which material can be used.

Development and validation of high-performance liquid chromatography-Orbitrap mass spectrometric method for quantification of NDMA in ranitidine drug products and evaluation of antioxidants as inhibitors of classical nitrosation reaction

RATIONALE

N-Nitroso dimethylamine (NDMA) is a mutagenic impurity detected in several ranitidine products. The amino functional group of ranitidine is a risk factor for classical nitrosation-induced NDMA formation in ranitidine drug products during storage conditions. The United States Food and Drug Administration (US FDA) recommended the use of antioxidants to control NDMA in drug products. Considering the need for sensitive analytics, a liquid chromatography/high-resolution mass spectrometry (LC-HRMS) method was developed and validated to detect NDMA in this pilot study to demonstrate the antioxidants as inhibitors of nitrosation reactions.

METHODS

The method, utilizing an EC-C18 column and tuned to atmospheric pressure chemical ionization/selected ion monitoring (APCI/SIM) mode, separated NDMA (m/z: 75.0553; tR: 3.71 min) and ranitidine (m/z: 315.1485; tR: 8.61 min). APCI mode exhibited four times higher sensitivity to NDMA than electrospray ionization (ESI) mode. Classical nitrosation of the dimethyl amino group of ranitidine was studied with sodium nitrite in solid pellets. Antioxidants (alpha-tocopherol, ascorbic acid, and trolox) were evaluated as NDMA attenuators in ranitidine pellets under vulnerable storage conditions. The developed method quantified NDMA levels in samples, extracted with methanol through vortex shaking for 45 min.

RESULTS

The method achieved a limit of detection (LOD) and limit of quantitation (LOQ) of 0.01 and 0.05 ng/mL, respectively, with linearity within 1-5000 ng/mL (R1: 0.9995). It demonstrated good intra-day and inter-day precision (% RSD [relative standard deviation]: <2) and accuracy (96.83%-101.72%). Nitrosation of ranitidine induced by nitrite was significant (p < 0.001; R2 = 0.9579) at various sodium nitrite levels. All antioxidants efficiently attenuated NDMA formation during ranitidine nitrosation. Ascorbic acid exhibited the highest NDMA attenuation (96.98%), followed by trolox (90.58%). This study recommends 1% ascorbic acid and trolox as potent NDMA attenuators in ranitidine drug products.

CONCLUSIONS

This study compared the effectiveness of antioxidants as NDMA attenuators in ranitidine under storage conditions susceptible to NDMA generation. The study concluded that ascorbic acid and trolox are potent inhibitors of NDMA formation and nitrosation attenuators in ranitidine drug products.

Basic regulatory science behind drug substance and drug product specifications of monoclonal antibodies and other protein therapeutics

In this review, we focus on providing basics and examples for each component of the protein therapeutic specifications to interested pharmacists and biopharmaceutical scientists with a goal to strengthen understanding in regulatory science and compliance. Pharmaceutical specifications comprise a list of important quality attributes for testing, references to use for test procedures, and appropriate acceptance criteria for the tests, and they are set up to ensure that when a drug product is administered to a patient, its intended therapeutic benefits and safety can be rendered appropriately. Conformance of drug substance or drug product to the specifications is achieved by testing an article according to the listed tests and analytical methods and obtaining test results that meet the acceptance criteria. Quality attributes are chosen to be tested based on their quality risk, and consideration should be given to the merit of the analytical methods which are associated with the acceptance criteria of the specifications. Acceptance criteria are set forth primarily based on efficacy and safety profiles, with an increasing attention noted for patient-centric specifications. Discussed in this work are related guidelines that support the biopharmaceutical specification setting, how to set the acceptance criteria, and examples of the quality attributes and the analytical methods from 60 articles and 23 pharmacopeial monographs. Outlooks are also explored on process analytical technologies and other orthogonal tools which are on-trend in biopharmaceutical characterization and quality control.

Development of a reliable method for determination of N-nitrosamines in medicines using disposable pipette extraction and HPLC-MS analysis

This study outlines the development and optimization of an analytical method using Disposable Pipette Extraction (DPX) followed by high performance liquid chromatography-mass spectrometry (HPLC-MS) analysis to determine NAs in medicines. HPLC-MS analysis utilized a reversed-phase and positive mode electrospray ion source. DPX parameters were optimized through univariate and multivariate analyses, including extraction phase, desorption solvent, sample pH, equilibrium time, and extraction/desorption cycles. The optimized conditions included a C18 extraction phase, methanol desorption solvent, pH at 7, an equilibrium time of 30 seconds, 2 extraction cycles, and 5 desorption cycles. Considering this method, it was possible to achieve a sample preparation step for the analysis of NAs in medicines using a minimal amount of extraction phase, sample, and desorption solvent. Furthermore, the total extraction procedure enables the extraction of NAs in around 4 minutes with NA recovery up to 98%. Analytical performance demonstrated precision and accuracy below 15% and a quantification limit of 1 ng mL-1, meeting validation requirements set by regulations worldwide. Thus, the DPX/HPLC-MS technique offers a faster and cost-effective method for analyzing NAs in medicines compared to traditional approaches. Besides, this method reduces solvent consumption and residue generation, enhancing environmental sustainability according to green chemistry principles.

Effect of Antioxidants in Medicinal Products on Intestinal Drug Transporters

The presence of mutagenic and carcinogenic N-nitrosamine impurities in medicinal products poses a safety risk. While incorporating antioxidants in formulations is a potential mitigation strategy, concerns arise regarding their interference with drug absorption by inhibiting intestinal drug transporters. Our study screened thirty antioxidants for inhibitory effects on key intestinal transporters-OATP2B1, P-gp, and BCRP in HEK-293 cells (OATP2B1) or membrane vesicles (P-gp, BCRP) using 3H-estrone sulfate, 3H-N-methyl quinidine, and 3H-CCK8 as substrates, respectively. The screen identified that butylated hydroxyanisole (BHA) and carnosic acid inhibited all three transporters (OATP2B1, P-gp, and BCRP), while ascorbyl palmitate (AP) inhibited OATP2B1 by more than 50%. BHA had IC50 values of 71 ± 20 µM, 206 ± 14 µM, and 182 ± 49 µM for OATP2B1, BCRP, and P-gp, respectively. AP exhibited IC50 values of 23 ± 10 µM for OATP2B1. The potency of AP and BHA was tested with valsartan, an OATP2B1 substrate, and revealed IC50 values of 26 ± 17 µM and 19 ± 11 µM, respectively, in HEK-293-OATP2B1 cells. Comparing IC50 values of AP and BHA with estimated intestinal concentrations suggests an unlikely inhibition of intestinal transporters at clinical concentrations of drugs formulated with antioxidants.

Synthesis and Trace-Level Quantification of Mutagenic and Cohort-of-Concern Ciprofloxacin Nitroso Drug Substance-Related Impurities (NDSRIs) and Other Nitroso Impurities Using UPLC-ESI-MS/MS-Method Optimization Using I-Optimal Mixture Design

Globally, the pharmaceutical industry has been facing challenges from nitroso drug substance-related impurities (NDSRIs). In the current study, we synthesized and developed a rapid new UPLC-MS/MS method for the trace-level quantification of ciprofloxacin NDSRIs and a couple of N-nitroso impurities simultaneously. (Q)-SAR methodology was employed to assess and categorize the genotoxicity of all ciprofloxacin N-nitroso impurities. The projected results were positive, and the cohort of concern (CoC) for all three N-nitroso impurities indicates potential genotoxicity. AQbD-driven I-optimal mixture design was used to optimize the mixture of solvents in the method. The chromatographic resolution was accomplished using an Agilent Poroshell 120 Aq-C18 column (150 mm × 4.6 mm, 2.7 μm) in isocratic elution mode with 0.1% formic acid in a mixture of water, acetonitrile, and methanol in the ratio of 475:500:25 v/v/v at a flow rate of 0.5 mL/min. Quantification was carried out using triple quadrupole mass detection with electrospray ionization (ESI) in a multiple reaction monitoring technique. The finalized method was validated successfully, affording ICH guidelines. All N-nitroso impurities revealed excellent linearity over the concentration range of 0.00125-0.0250 ppm. The Pearson correlation coefficient of each N-nitroso impurity was >0.999. The method accuracy recoveries ranged from 93.98 to 108.08% for the aforementioned N-nitrosamine impurities. Furthermore, the method was effectively applied to quantify N-nitrosamine impurities simultaneously in commercially available formulated samples, with its efficiency recurring at trace levels. Thus, the current method is capable of determining the trace levels of three N-nitroso ciprofloxacin impurities simultaneously from the marketed tablet dosage forms for commercial release and stability testing.

Mechanochemistry for Healthcare: Revealing the Nitroso Derivatives Genesis in the Solid State

Nitroso derivatives with unique characteristics have been extensively studied in various fields, including biology and clinical research. Although there has been substantial investigation of "nitrosable" components in many drugs and commonly consumed nutrients, there is still a need for a higher awareness about their formation and characterization. This study demonstrates how these derivatives can be produced through a mechanochemical procedure under solid-state conditions. The results include synthesizing previously unknown compounds with potential biological and pharmaceutical applications, such as a nitrosamine derived from a Diclofenac-like structure.

Recent Advances in Electrochemical Sensors for Formaldehyde

Formaldehyde, a ubiquitous indoor air pollutant, plays a significant role in various biological processes, posing both environmental and health challenges. This comprehensive review delves into the latest advancements in electrochemical methods for detecting formaldehyde, a compound of growing concern due to its widespread use and potential health hazards. This review underscores the inherent advantages of electrochemical techniques, such as high sensitivity, selectivity, and capability for real-time analysis, making them highly effective for formaldehyde monitoring. We explore the fundamental principles, mechanisms, and diverse methodologies employed in electrochemical formaldehyde detection, highlighting the role of innovative sensing materials and electrodes. Special attention is given to recent developments in nanotechnology and sensor design, which significantly enhance the sensitivity and selectivity of these detection systems. Moreover, this review identifies current challenges and discusses future research directions. Our aim is to encourage ongoing research and innovation in this field, ultimately leading to the development of advanced, practical solutions for formaldehyde detection in various environmental and biological contexts.

Nitrosamine Impurities in Pharmaceuticals: An Empirical Review of their Detection, Mechanisms, and Regulatory Approaches

Since their discovery in valsartan-containing drugs, nitrosamine impurities have emerged as a significant safety problem in pharmaceutical products, prompting extensive recalls and suspensions. Valsartan, candesartan, irbesartan, olmesartan, and other sartans have been discovered to have additional nitrosamine impurities, such as N-nitroso-N-methyl-4-aminobutyric acid (NMBA), N-nitroso-Di-isopropyl amine (NDIPA), N-nitroso-Ethyl-Isopropyl amine (NEIPA), and N-nitroso-Diethyl amine (NDEA). Concerns about drug safety have grown in response to reports of nitrosamine contamination in pharmaceuticals, such as pioglitazone, rifampin, rifapentine, and varenicline. This review investigates the occurrence and impact of nitrosamine impurities in sartans and pharmaceutical goods, as well as their underlying causes. The discussion emphasizes the significance of comprehensive risk assessment and mitigation approaches at various phases of medication development and manufacturing. The link between amines and nitrosamine impurities is also investigated, with an emphasis on pH levels and the behaviour of primary, secondary, tertiary, and quaternary amines. Regulations defining standards for nitrosamine assessment and management, such as ICH Q3A-Q3E and ICH M7, are critical in resolving impurity issues. Furthermore, the Global Substance Registration System (GSRS) is underlined as being critical for information sharing and product safety in the pharmaceutical industry. The review specifically focuses on the relationship between ranitidine and N-nitroso dimethyl amine (NDMA) in the context of the implications of nitrosamine contamination on patient safety and medicine supply. The importance of regulatory authorities in discovering and correcting nitrosamine impurities is highlighted in order to improve patient safety, product quality, and life expectancy. Furthermore, the significance of ongoing study and attention to nitrosamine-related repercussions for increasing pharmaceutical safety and overall public health is emphasized.

Bumetanide as a Model NDSRI Substrate: N-nitrosobumetanide Impurity Formation and its Inhibition in Bumetanide Tablets

Nitrosamine compounds are classified as potential human carcinogens, the origin of these impurities can be broadly classified in two categories, nitrosamine impurity found in drug products that are not associated with the Active Pharmaceutical Ingredient (API), such as N-nitrosodimethylamine (NDMA) or nitrosamine impurities associated with the API, such as nitrosamine drug substance-related impurities (NDSRIs). The mechanistic pathway for the formation of these two classes of impurities can be different and the approach to mitigate the risk should be tailored to address the specific concern. In the last couple of years number of NDSRIs have been reported for different drug products. Though, not the only contributing factor for the formation of NDSIRs, it is widely accepted that the presence of residual a nitrites/nitrates in the components used in the manufacturing of the drug products can be the primary contributor to the formation of NDSRIs. Approaches to mitigate the formation of NDSRIs in drug products include the use of antioxidants or pH modifiers in the formulation. The primary objective of this work was to evaluate the role of different inhibitors (antioxidants) and pH modifiers in tablet formulations prepared in-house using bumetanide (BMT) as a model drug to mitigate the formation of N-nitrosobumetanide (NBMT). A multi-factor study design was created, and several bumetanide formulations were prepared by wet granulation with and without sodium nitrite spike (100 ppm) and different antioxidants (ascorbic acid, ferulic acid or caffeic acid) at three concentrations (0.1%, 0.5% or 1% of the total tablet weight). Formulations with acidic and basic pH were also prepared using 0.1 N hydrochloric acid and 0.1 N sodium bicarbonate, respectively. The formulations were subjected to different storage (temperature and humidity) conditions over 6 months and stability data was collected. The rank order of N-nitrosobumetanide inhibition was highest with alkaline pH formulations, followed by formulations with ascorbic acid, caffeic acid or ferulic acid present. In summary, we hypothesize that maintaining a basic pH or the addition of an antioxidant in the drug product can mitigate the conversion of nitrite to nitrosating agent and thus reduce the formation of bumetanide nitrosamines.

Simultaneous analysis of carcinogenic N-nitrosamine impurities in metformin tablets using on-line in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry

Contamination of active pharmaceutical ingredients (APIs) and pharmaceutical preparations with carcinogenic N-nitrosamines has led to recalls of these products and supply shortages to patients. The present study describes the development of a highly sensitive method for simultaneous analysis of seven N-nitrosamines using on-line in-tube solid-phase microextraction (IT-SPME) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine their actual contamination in metformin tablets. Using a Carboxen 1006 PLOT capillary as the extraction device for IT-SPME, these compounds were efficiently extracted and concentrated 6‒24-fold by subjecting 40 µL of sample to 25 repeated draw/eject cycles at a rate of 0.2 mL/min. The seven N-nitrosamines were separated within 11 min by gradient elution with 0.1 % formic acid solution and acetonitrile as the mobile phase using a CAPCELL PAK C18 MGII column and detected by multiple reaction monitoring in positive ion mode. The calibration curve showed linearity in the range 0.2‒50 ng/mL and detection limits (S/N = 3) in the range 3‒112 pg/mL. The intra-day and inter-day precisions were less than 5.5 % and 7.0 % (n = 6), respectively, with accuracies ranging from 93‒117 %. Following ultrasonic extraction with water, centrifugation and filtration of the supernatant liquid through a membrane filter, the N-nitrosamine impurities in metformin tablets could be analyzed by IT-SPME/LC‒MS/MS. Their limits of quantification (S/N = 10) were 0.1‒5.1 pg/mg API and recoveries ranged from 87‒102 %. Analysis of eight metformin tablets from eight manufacturers showed that 5.8‒7.5 pg/mg N-nitrosodimethylamine were present in three tablets, with no other N-nitrosamines detected in any of the eight tablets. This method may be useful in testing for N-nitrosamine impurities in pharmaceutical preparations.

Development and Validation of LC-MS/MS Method for the Determination of 1-Methyl-4-Nitrosopiperazine (MNP) in Multicomponent Products with Rifampicin-Analytical Challenges and Degradation Studies

Rifampicin is an essential medicine for treating and preventing tuberculosis (TB). TB is a life-threatening infectious disease and its prevention and treatment are public health imperatives. In the time of a global crisis of nitrosamine contamination of medicinal products, patient safety and a reduction in the number of drug recalls at the same time are crucial. In this work, the LC-MS/MS method was developed for the determination of the 1-methyl-4-nitrosospiperazine (MNP), a genotoxic nitrosamine impurity in various products containing rifampicin at a 5.0 ppm limit level according to Food and Drug Administration (FDA). Extraction with neutralization was necessary due to the matrix and solvent effect associated with the complexity of the rifampicin product. The developed method was validated in accordance with regulatory guidelines. Specificity, accuracy, precision, limit of detection, and limit of quantification parameters were evaluated. The recovery of the MNP was 100.38 ± 3.24% and the intermediate precision was 2.52%. The contamination of MNP in Rifampicin originates in the manufacturing process of the drug. Furthermore, the results of the forced degradation experiments show that the formation of MNP is possible by two mechanisms: through degradation of rifampicin and the oxidation of 1-amino-4-methyl-piperazine. This article points out that it is necessary to monitor and describe degradation products and the mechanism of degradation of potentially affected active pharmaceutical ingredient (API) with respect to the formation of nitrosamines during stress testing, as it was done in the following work for rifampicin in multicomponent products.

Performance Characteristics of Mass Spectrometry-Based Analytical Procedures for Quantitation of Nitrosamines in Pharmaceuticals: Insights from an Inter-laboratory Study

With the discovery of carcinogenic nitrosamine impurities in pharmaceuticals in 2018 and subsequent regulatory requirements for risk assessment for nitrosamine formation during pharmaceutical manufacturing processes, storage or from contaminated supply chains, effective testing of nitrosamines has become essential to ensure the quality of drug substances and products. Mass spectrometry has been widely applied to detect and quantify trace amounts of nitrosamines in pharmaceuticals. As part of an effort by regulatory authorities to assess the measurement variation in the determination of nitrosamines, an inter-laboratory study was performed by the laboratories from six regulatory agencies with each of the participants using their own analytical procedures to determine the amounts of nitrosamines in a set of identical samples. The results demonstrated that accurate and precise quantitation of trace level nitrosamines can be achieved across multiple analytical procedures and provided insight into the performance characteristics of mass spectrometry-based analytical procedures in terms of accuracy, repeatability and reproducibility.

Rapid screening of high-priority N-nitrosamines in pharmaceutical, forensic, and environmental samples with paper spray ionization and filter cone spray ionization-mass spectrometry

RATIONALE

The burgeoning concern of N-nitrosamine (NAM) contamination found in various pharmaceutical compositions has increased the demand for rapid and reliable screening methods to better assess the breadth of the problem. These carcinogenic compounds are also found in food, water, and soil, and they have been used in poison-related homicides.

METHODS

A combination of complementary, ambient ionization methods, paper spray ionization (PSI) and filter cone spray ionization (FCSI)-mass spectrometry (MS), was characterized towards trace-level residue screening of select NAMs (e.g., N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine) directly from complex and problematic matrices of interest, including prescription and over-the-counter tablets, drinking water, soil, and consumable goods. Spectral data for analyte confirmation and detection limit studies were collected using a Thermo LCQ Fleet ion trap mass spectrometer.

RESULTS

PSI-MS and FCSI-MS readily produced mass spectral data marked by their simplicity (e.g., predominantly protonated molecular ions observed) and congruence with traditional electrospray ionization mass spectra in under 2 min. per sample. Both methods proved robust to the complex matrices tested, yielding ion signatures for target NAMs, as well as active pharmaceutical ingredients for analyzed tablets, flavorants inherent to food products, etc. Low part-per-million detection limits were observed but were shown dependent on sample composition.

CONCLUSIONS

PSI-MS and FCSI-MS were successful in detecting trace-level NAMS in complex liquid- and solid-phase matrices with little to no prior preparation. This work suggests that these methodologies can provide a means for assessing problematic pharmaceutical adulterants/degradants for expedited quality control, as well as enhancing environmental stewardship efforts and forensic investigations.

A survey of industrial N-nitrosamine discharges in Switzerland

N-nitrosamines are formed during different industrial processes and are of significant concern due to their carcinogenic and mutagenic properties. This study reports concentrations of N-nitrosamines in eight different industrial wastewater treatment plants in Switzerland and the variability of their abundance. Only four N-nitrosamines species, N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosodibutylamine (NDPA) and N-nitrosomorpholine (NMOR) were above the limit of quantification in this campaign. Remarkably high concentrations (i.e. up to 975 μg NDMA/L, 90.7 μg NDEA/L, 1.6 μg NDPA/L and 710 μg NMOR/L) of these N-nitrosamines were detected at seven of eight sites. These concentrations are two to five orders of magnitude higher than those typically detected in municipal wastewater effluents. These results suggest that industrial effluents may be a major source of N-nitrosamines. Although very high concentrations of N-nitrosamine have been detected in industrial discharges, various processes in surface water can partially mitigate their concentrations (e.g. photolysis, biodegradation and volatilization) and hence the risk to human health and aquatic ecosystems. Nevertheless, there is little information on long-term effects on aquatic organisms and therefore the discharge of N-nitrosamines to the environment should be avoided until the impact on ecosystems is assessed. During winter a less efficient mitigation of N-nitrosamines can be expected (lower biological activity, less sunlight) and therefore, emphasis should be put on this season in future risk assessment studies.

A collaborative study of the impact of N-nitrosamines presence and ARB recall on ARB utilization - results from IQVIA™ Disease Analyzer Germany

PURPOSE

Regulators are increasingly concerned with  the impact of recalls on drug adherence. In 2018, N-nitrosamines impurities were detected in valsartan containing medical products. Concerned products were immediately recalled in July 2018 by regulatory agencies internationally. In Germany, recalls were issued for valsartan, losartan and irbesartan from July 2018 to March 2019. This study examined angiotensin II receptor blocker (ARB) utilization trends and switching patterns in Germany before and after July 2018.

METHODS

Patients prescribed ARBs from January 2014 to June 2020 in general practices in Germany were included in a collaborative framework common protocol drug utilization study led by the US Food and Drug Administration. Trends in monthly and quarterly proportions of total ARB prescribing were analysed for individual ARBs using descriptive statistics and interrupted time series analysis. The rate of switching to an alternative ARB was analysed before and after the recalls.

RESULTS

The proportion of valsartan prescriptions immediately decreased from 35.9 to 17.8% following the first recalls in July 2018, mirrored by an increased proportion for candesartan. Increased switching from valsartan to candesartan was observed. No increased switching was observed after losartan recalls, whereas for irbesartan, increased switching was observed 6-12 months after the last recall. Increased switching from ARBs to angiotensin-converting enzyme (ACE) inhibitors or ARB treatment discontinuations were not observed.

CONCLUSION

This study showed that patients were able to continue ARB treatment despite the July 2018-March 2019 recalls, although many patients needed to switch to an alternative ARB. The duration of the impact of ARB recalls appeared to be limited.

Modified NAP test: A simple and Responsive Nitrosating Methodology for Risk Evaluation of NDSRIs

N-Nitroso compounds have been listed as one of the cohorts of concern as per ICH M7. In recent years, the regulatory focus has shifted from common nitrosamines to nitroso-impurities of drug products. Thus, the detection and quantification of unacceptable levels of nitrosamine drug substance-related impurities are of great concern for analytical scientists during drug development. Moreover, risk assessment of nitrosamines is also an essential part of the regulatory filling. For risk assessment, the Nitrosation Assay Procedure suggested by WHO expert group in 1978 is being followed. However, it could not be adopted by the pharmaceutical industries due to the limitation of drug solubility and artefact formation in the test conditions. In this work, we have optimized an alternative nitrosation test to investigate the likelihood of direct nitrosation. The technique is simple, where the drug solubilized in an organic solvent is incubated at 37°C with a nitrosating agent named tertiary butyl nitrite in a 1:10 molar ratio. LC-UV/MS-based chromatographic method was developed to separate drug substances and respective nitrosamine impurities using the C18 analytical column. The methodology was successfully tested on five drugs with varying structural chemistry. The procedure is straightforward, effective, and quick for the nitrosation of secondary amines. This modified nitrosation test and WHO prescribed nitrosation test have been compared and found that the modified methodology is more effective and time-saving.

A comprehensive review of sources of nitrosamine contamination of pharmaceutical substances and products

N-nitrosamines are carcinogenic impurities most commonly found in groundwater, treated water, foods, beverages and consumer products. The recent discovery of N-nitrosamines in pharmaceutical products and subsequent recalls pose a significant health risk to patients. Initial investigation by the regulatory agency identified Active Pharmaceutical Ingredients (API) as a source of contamination. However, N-nitrosamine formation during API synthesis is a consequence of numerous factors like chemistry selection for synthesis, contaminated solvents and water. Furthermore, apart from API, N-nitrosamines have also been found to embed in the final product due to degradation during formulation processing or storage through contaminated excipients and printing inks. The landscape of N-nitrosamine contamination of pharmaceutical products is very complex and needs a comprehensive compilation of sources responsible for N-nitrosamine contamination of pharmaceutical products. Therefore, this review aims to extensively compile all the reported and plausible sources of nitrosamine impurities in pharmaceutical products. The topics like risk assessment and quantitative strategies to estimate nitrosamines in pharmaceutical products are out of the scope of this review.

Current status and prospects of development of analytical methods for determining nitrosamine and N-nitroso impurities in pharmaceuticals

Nitrosamine impurities in pharmaceuticals have recently been concerned for several national regulatory agencies to avoid carcinogenic and mutagenic effects in patients. The demand for highly sensitive and specific analytical methods with LOQs in the ppb and sub-ppb ranges is among the most significant challenges facing analytical scientists. In addition, artifactual nitrosamine formation during sample preparation and injection leading to overestimation of nitrosamines has received considerable attention. Numerous analytical methodologies have been reported for quantifying nitrosamine impurities in active pharmaceutical ingredients and medicinal products at the interim limit criteria as preventive measures. In this review, we meticulously discuss those reported gas and liquid chromatographic methods for nitrosamine determination in pharmaceuticals in aspects of chromatographic conditions and sensitivity of detection. We also introduce the potential of novel fluorescence-based methods recently developed to rapidly screen nitrosamine impurities. In addition, the review assesses the nitrosation assay procedure (NAP test), which is expected to be a future preventive measure for screening potential nitrosation and identifying suspected contamination with N-nitroso or other potential mutagenic impurities during the drug development process.

DNA Alkylation Damage by Nitrosamines and Relevant DNA Repair Pathways

Nitrosamines occur widespread in food, drinking water, cosmetics, as well as tobacco smoke and can arise endogenously. More recently, nitrosamines have been detected as impurities in various drugs. This is of particular concern as nitrosamines are alkylating agents that are genotoxic and carcinogenic. We first summarize the current knowledge on the different sources and chemical nature of alkylating agents with a focus on relevant nitrosamines. Subsequently, we present the major DNA alkylation adducts induced by nitrosamines upon their metabolic activation by CYP450 monooxygenases. We then describe the DNA repair pathways engaged by the various DNA alkylation adducts, which include base excision repair, direct damage reversal by MGMT and ALKBH, as well as nucleotide excision repair. Their roles in the protection against the genotoxic and carcinogenic effects of nitrosamines are highlighted. Finally, we address DNA translesion synthesis as a DNA damage tolerance mechanism relevant to DNA alkylation adducts.

Analytical Method Capable of Quantifying Eight Nitrosamine Impurities from Five Different Commercially Available Metformin Formulations with Glipizide, Glibenclamide, Gliclazide, Evogliptin, and Glimepiride by Ultra High Performance Liquid Chromatography Tripple Quadrupole Mass Spectrometry

Metformin and its combinations are widely used to treat type 2 diabetes. The drugs commonly used in combination with Metformin are Glipizide, Glibenclamide, Gliclazide, Evogliptin, and Glimepiride. Combination therapy is preferred over monotherapy of Metformin in most diabetics. About eighteen pharmaceutical manufacturers have lately recalled metformin formulation batches from the U.S. market due to N-nitrosodimethylamine (NDMA) impurities based on the food and drug administration (USFDA) guideline "Control of Nitrosamine in Human Drugs." European Medicines Agency (EMA) and Health Canada have also established guidelines for nitrosamine impurities. Nitrosamines are well-known mutagenic impurities and probable human carcinogens found in pharmaceutical formulations. Thus, global regulatory agencies require pharmaceutical and formulation manufacturers to complete risk assessments for nitrosamine impurities for patient safety. Therefore, drug manufacturers must develop analytical techniques for monitoring trace nitrosamine impurities. Quantifying nitrosamine impurities in formulations requires modern equipment like LC-MS/MS and great intellect. The present study intends to give a single pre-packaged LC-MS/MS method parameters, including liquid chromatography and triple quadrupole mass spectrometer configuration. This method could quantify eight nitrosamine impurities from five different Metformin combinations (Metformin with Glipizide, Glibenclamide, Gliclazide, Evogliptin, and Glimepiride). The atmospheric pressure chemical ionisation (APCI) was used as an ionisation source, and the mass spectrometer was set to multiple reaction monitoring (MRM) mode for all eight nitrosamine impurities. A unified pre-packaged analytical setup allows analytical chemists to develop a reliable, sensitive, robust, and precise method for quantifying eight nitrosamine impurities from five different Metformin formulations of varying manufacturers. This analytical method saves time, money, and the environment using fewer pharmaceutical chemicals.

Chemometric-assisted surface-enhanced Raman spectroscopy for metformin determination using gold nanoparticles as substrate

A fast, simple, and reliable method for determination of metformin was developed by coupling surface-enhanced Raman spectroscopy (SERS) with chemometric methods. This relayed on the utilization of a portable Raman spectrometer and of citrate stabilized gold nanoparticles (AuNPs) as substrate, to carry out the measurement of SERS scattering signals, thus assuring improved sensitivity. The obtained datasets were analysed using principal component analysis (PCA) and partial least squares (PLS) regression. Upon optimization of the PLS model, in terms of latent variables, spectral region and pre-processing techniques, RMSECV and R²_CV values of 0.42 mg/L and 0.94, respectively, were obtained. The optimized PLS regression model was further validated with the projection of commercial pharmaceutical samples, providing good results in terms of R²_P (0.97), RE (4.54 %) and analytical sensitivity (2.13 mg/L).

Nitroso Impurities in Drug Products: An Overview of Risk Assessment, Regulatory Milieu, and Control Strategy

Many nitrosamines have been recognized to be carcinogenic for many decades. Despite the fact that several nitrosamine precursors are frequently used in the manufacturing of pharmaceutical products, their potential presence in pharmaceutical products has previously been overlooked due to a lack of understanding on how they form during the manufacturing process. From the risk assessment, it is clear that nitrosamines or their precursors may be present in any component of the finished dosage form. As a risk mitigation strategy, components with a high potential to form nitrosamine should be avoided. In the absence of suitable alternatives, sufficient measures to maintain nitrosamines below acceptable intake levels must be applied. Excipient manufacturing pathways must be extensively studied in order to identify probable excipient components that may contribute to nitrosamine formation. The manufacturers must not solely rely on pharmacopeial specifications for APIs and excipients, rather, they should also develop and implement additional strategies to control nitrosamine impurities. The formulation can be supplemented with nitrosating inhibitors, such as vitamin C, to stop the generation of nitrosamine. The purpose of this review is to identify key risk factors with regard to nitrosamine formation in pharmaceutical dosage forms and provide an effective control strategy to contain them below acceptable daily intake limits.

An update on the current status and prospects of nitrosation pathways and possible root causes of nitrosamine formation in various pharmaceuticals

Over the last two years, global regulatory authorities have raised safety concerns on nitrosamine contamination in several drug classes, including angiotensin II receptor antagonists, histamine-2 receptor antagonists, antimicrobial agents, and antidiabetic drugs. To avoid carcinogenic and mutagenic effects in patients relying on these medications, authorities have established specific guidelines in risk assessment scenarios and proposed control limits for nitrosamine impurities in pharmaceuticals. In this review, nitrosation pathways and possible root causes of nitrosamine formation in pharmaceuticals are discussed. The control limits of nitrosamine impurities in pharmaceuticals proposed by national regulatory authorities are presented. Additionally, a practical and science-based strategy for implementing the well-established control limits is notably reviewed in terms of an alternative approach for drug product N-nitrosamines without published AI information from animal carcinogenicity testing. Finally, a novel risk evaluation strategy for predicting and investigating the possible nitrosation of amine precursors and amine pharmaceuticals as powerful prevention of nitrosamine contamination is addressed.

Development of a sensitive LC-APCI-MS/MS method for simultaneous determination of eleven nitrosamines in valsartan and irbesartan with a simple extraction approach

Nitrosamines (NAs) are potent genotoxic agents (GAs) in several animal species, and some are classified as probable or possible human carcinogens by the International Agency for Research on Cancer (IARC). In July 2018, angiotensin II receptor blockers (ARBs) which are used to treat high blood pressure have been recalled owing to contamination with NAs. In this study, a simple and sensitive method for the determination of eleven NAs in a single analysis was developed, using atmospheric pressure chemical ionisation source coupled liquid chromatography tandem mass spectrometer (LC-APCI-MS/MS). By performing the 17 min-run in dynamic multiple reaction monitoring (dMRM) mode, eleven NAs were separated on a Poroshell HPH C18 (4.6 × 150 mm, 2.7 µm) column with gradient elution implementing mobile phase A consisting of 0.2 % formic acid in water and mobile phase B consisting of methanol. The developed analytical method was successfully applied in both active pharmaceutical ingredients (APIs) and finished products (FPs) of valsartan and irbesartan with straightforward and effective extraction procedures. Good linearity with a correlation coefficient (R²) > 0.996 was achieved over the concentration in a range of 0.5-50 ng/mL. The limits of detection (LODs) ranged in 0.001-0.008 ppm and limits of quantitation (LOQs) ranged in 0.008-0.05 ppm of the method fulfilled thresholds of US Food and Drug Administration (US-FDA) and European Medicines Agency (EMA) for testing of GAs in valsartan and irbesartan. The accuracy of the proposed method ranged from 73.1 % to 115.2 % for APIs and the relative standard deviation (RSD %) was ≤11.3 while these validation parameters were in the range of 80.2-128.5 % and ≤ 10.6 for FPs, respectively.

Does the Red Shift in UV-Vis Spectra Really Provide a Sensing Option for Detection of N-Nitrosamines Using Metalloporphyrins?

N-nitrosamines are widespread cancerogenic compounds in human environment, including water, tobacco products, food, and medicinal products. Their presence in pharmaceuticals has recently led to several recalls of important medicines from the market, and strict controls and tight limits of N-nitrosamines are now required. Analytical determination of N-nitrosamines is expensive, laborious, and time-inefficient making development of simpler and faster techniques for their detection crucial. Several reports published in the previous decade have demonstrated that cobalt porphyrin-based chemosensors selectively bind N-nitrosamines, which produces a red shift of characteristic Soret band in UV-Vis spectra. In this study, a thorough re-evaluation of metalloporphyrin/N-nitrosamine adducts was performed using various characterization methods. Herein, we demonstrate that while N-nitrosamines can interact directly with cobalt-based porphyrin complexes, the red shift in UV-Vis spectra is not selectively assured and might also result from the interaction between impurities in N-nitrosamines and porphyrin skeleton or interaction of other functional groups within the N-nitrosamine structure and the metal ion within the porphyrin. We show that pyridine nitrogen is the interacting atom in tobacco-specific N-nitrosamines (TSNAs), as pyridine itself is an active ligand and not the N-nitrosamine moiety. When using Co(II) porphyrins as chemosensors, acidic and basic impurities in dialkyl N-nitrosamines (e.g., formic acid, dimethylamine) are also UV-Vis spectra red shift-producing species. Treatment of these N-nitrosamines with K₂CO₃ prevents the observed UV-Vis phenomena. These results imply that cobalt-based metalloporphyrins cannot be considered as selective chemosensors for UV-Vis detection of N-nitrosamine moiety-containing species. Therefore, special caution in interpretation of UV-Vis red shift for chemical sensors is suggested.

Regulatory Experiences with Root Causes and Risk Factors for Nitrosamine Impurities in Pharmaceuticals

N-Nitrosamines (also referred to as nitrosamines) are a class of substances, many of which are highly potent mutagenic agents which have been classified as probable human carcinogens. Nitrosamine impurities have been a concern within the pharmaceutical industry and by regulatory authorities worldwide since June 2018, when regulators were informed of the presence of N-nitrosodimethylamine (NDMA) in the angiotensin-II receptor blocker (ARB) medicine, valsartan.  Since that time, regulatory authorities have collaborated to share information and knowledge on issues related to nitrosamines with a goal of promoting convergence on technical issues and reducing and mitigating patient exposure to harmful nitrosamine impurities in human drug products. This paper shares current scientific information from a quality perspective on risk factors and potential root causes for nitrosamine impurities, as well as recommendations for risk mitigation and control strategies.

Strategies for Assessing Acceptable Intakes for Novel N-Nitrosamines Derived from Active Pharmaceutical Ingredients

The detection of N-nitrosamines, derived from solvents and reagents and, on occasion, the active pharmaceutical ingredient (API) at higher than acceptable levels in drug products, has led regulators to request a detailed review for their presence in all medicinal products. In the absence of rodent carcinogenicity data for novel N-nitrosamines derived from amine-containing APIs, a conservative class limit of 18 ng/day (based on the most carcinogenic N-nitrosamines) or the derivation of acceptable intakes (AIs) using structurally related surrogates with robust rodent carcinogenicity data is recommended. The guidance has implications for the pharmaceutical industry given the vast number of marketed amine-containing drugs. In this perspective, the rate-limiting step in N-nitrosamine carcinogenicity, involving cytochrome P450-mediated α-carbon hydroxylation to yield DNA-reactive diazonium or carbonium ion intermediates, is discussed with reference to the selection of read-across analogs to derive AIs. Risk-mitigation strategies for managing putative N-nitrosamines in the preclinical discovery setting are also presented.

Assessment of a Diverse Array of Nitrite Scavengers in Solution and Solid State: A Study of Inhibitory Effect on the Formation of Alkyl-Aryl and Dialkyl N-Nitrosamine Derivatives

The ubiquitous presence of mutagenic and potentially carcinogenic N-nitrosamine impurities in medicines has become a major issue in the pharmaceutical industry in recent years. Rigorous mitigation strategies to limit their amount in drug products are, therefore, needed. The removal of nitrite, which is a prerequisite reagent for the N-nitrosation of amines, has been acknowledged as one of the most promising strategies. We have conducted an extensive literature search to identify nineteen structurally diverse nitrite scavengers and screened their activity experimentally under pharmaceutically relevant conditions. In the screening phase, we have identified six compounds that proved to have the best nitrite scavenging properties: ascorbic acid (vitamin C), sodium ascorbate, maltol, propyl gallate, para-aminobenzoic acid (PABA), and l-cysteine. These were selected for investigation as inhibitors of the formation of N-methyl-N-nitrosoaniline (NMA) from N-methylaniline and N-nitroso-N’-phenylpiperazine (NPP) from N-phenylpiperazine in both solution and model tablets. Much faster kinetics of NMA formation compared to NPP was observed, but the former was less stable at high temperatures. Vitamin C, PABA, and l-cysteine were recognized as the most effective inhibitors under most studied conditions. The nitrite scavenging activity does not directly translate into N-nitrosation inhibitory effectiveness, indicating other reaction pathways may take place. The study presents an important contribution to identifying physiologically acceptable chemicals that could be added to drugs to prevent N-nitrosation during manufacture and storage.

Current trends in read-across applications for chemical risk assessments and chemical registrations in the Republic of Korea

Read-across, an alternative approach for hazard assessment, has been widely adopted when in vivo data are unavailable for chemicals of interest. Read-across is enabled via in silico tools such as quantitative structure activity relationship (QSAR) modeling. In this study, the current status of structure activity relationship (SAR)-based read-across applications in the Republic of Korea (ROK) was examined considering both chemical risk assessments and chemical registrations from different sectors, including regulatory agencies, industry, and academia. From the regulatory perspective, the Ministry of Environment (MOE) established the Act on Registration and Evaluation of Chemicals (AREC) in 2019 to enable registrants to submit alternative data such as information from read-across instead of in vivo data to support hazard assessment and determine chemical-specific risks. Further, the Ministry of Food and Drug Safety (MFDS) began to consider read-across approaches for establishing acceptable intake (AI) limits of impurities occurring during pharmaceutical manufacturing processes under the ICH M7 guideline. Although read-across has its advantages, this approach also has limitations including (1) lack of standardized criteria for regulatory acceptance, (2) inconsistencies in the robustness of scientific evidence, and (3) deficiencies in the objective reliability of read-across data. The application and acceptance rate of read-across may vary among regulatory agencies. Therefore, sufficient data need to be prepared to verify the hypothesis that structural similarities might lead to similarities in properties of substances (between source and target chemicals) prior to adopting a read-across approach. In some cases, additional tests may be required during the registration process to clarify long-term effects on human health or the environment for certain substances that are data deficient. To improve the quality of read-across data for regulatory acceptance, cooperative efforts from regulatory agencies, academia, and industry are needed to minimize limitations of read-across applications.

Development and Validation of an HPLC-FLD Method for the Determination of NDMA and NDEA Nitrosamines in Lisinopril Using Pre-Column Denitrosation and Derivatization Procedure

In order to meet the analytical requirements of the European Medicines Agency (EMA), a new HPLC-FLD method was successfully developed using dansyl chloride for the derivatization and determination of the genotoxic impurities N-Nitrosodimethylamine (NDMA) and N-Nitrosodiethylamine (NDEA) in Lisinopril API and its final product. Samples’ pretreatment includes liquid–liquid microextraction, denitrosation, and derivatization steps. To optimize the process, the parameters contributing to high sensitivity and yielding reliable results were thoroughly studied and optimized using one-factor-at-a-time and experimental design approaches. The analytes were pre-column derivatized with Dansyl-Cl and analyzed by HPLC-fluorescence (λem/λem = 340/530) using a C18 column and a mixture of phosphate buffer (pH = 2.8; 20 mM)/acetonitrile 55:45 v/v as the mobile phase. The six-level concentration calibration was shown to be linear, with R equal to 0.9995 for both analytes. The limit of detection (LOD) was satisfactory and equal to 4.7 and 0.04 ng/mL for NDMA and NDEA, respectively. Precision was less than 13.4% in all cases, and the average recoveries were equal to 109.2 and 98.1% for NDMA and NDEA, respectively. The proposed procedure is relatively easy, rapid, and suitable for the determination of the two nitrosamines in routine analysis tests.

Genotoxicity evaluation of a valsartan-related complex N-nitroso-impurity

Recently, the formation of genotoxic and carcinogenic N-nitrosamines impurities during drug manufacturing of tetrazole-containing angiotensin-II blockers has been described. However, drug-related (complex) nitrosamines may also be generated under certain conditions, i.e., through nitrosation of vulnerable amines in drug substances in the presence of nitrite. An investigation of valsartan drug substance showed that a complex API-related N-nitrosamine chemically designated as (S)-2-(((2'-(1H-tetrazol-5-yl)-[1,1'-biphenyl]-4-yl)methyl)(nitroso)amino)-3-methylbutanoic acid (named 181-14) may be generated. 181-14 was shown to be devoid of a mutagenic potential in the Non-GLP Ames test. According to ICH M7 (R1) (2018), impurities that are not mutagenic in the Ames test would be considered Class 5 impurities and limited according to ICH Q3A (R2) and B (R2) (2006) guidelines. However, certain regulatory authorities raised the concern that the Ames test may not be sufficiently sensitive to detect a mutagenic potential of nitrosamines and requested a confirmatory in vivo study using a transgenic animal genotoxicity model. Our data show that 181-14 was not mutagenic in the transgenic gene mutation assay in Muta^TMMice. The data support the conclusion that the Ames test is an adequate and sensitive test system to assess a mutagenic potential of nitrosamines.

Development and evaluation of a HILIC-MS method for the determination of amino acid and non-amino acid impurities in histidine

Developing analytical methods to assure and control the quality of amino acids has long been a challenge for food ingredient, dietary supplement, and pharmaceutical industries due to the high polarity and the absence of chromophores in many amino acids; the situation worsens further by the lack of information of impurities that could potentially be introduced during the manufacturing processes. Herein we utilize a four-step strategy including impurity identification, method development, sample analysis, and targeted impurity detection and quantitation to demystify the impurity profiles of amino acids. The effectiveness of the approach is highlighted using histidine as an example. Analysis of histidine manufacturing and degradation processes led to the identification of 12 potential impurities of histidine, including amino acids (arginine, lysine, asparagine, aspartic acid, alanine, and glycine) and non-amino acid impurities (histamine, histidinol, 4-imidazoleacrylic acid, 4-imidazoleacetic acid, β-imidazolelactic acid, and urea). A HILIC method using Poroshell 120 HILIC-Z column (2.1 × 100 mm, 2.7 µm) and a mobile phase system consisting of ammonium formate buffer at pH 3.2 in water and 0.1% formic acid in acetonitrile coupled with a single quadrupole mass spectrometer was developed for the detection and quantitation of the proposed impurities. Evaluation of 11 commercial histidine samples using the developed method revealed distinct impurity profiles, as a fingerprint for each sample; seven of the 12 proposed impurities were detected in histidine samples tested. The developed method was evaluated in terms of specificity, linearity, range, accuracy, precision, and sensitivity (LOQ: 2.5-60.6 ng/mL) for its suitability for compendial applications. Given the high degree of overlap between the proposed and the detected impurities, the approach could be utilized to strengthen USP standards for controlling the quality of histidine. Extension of the strategy to the analysis of other amino acids is currently underway.

Mass spectrometry based fragmentation patterns of nitrosamine compounds

RATIONALE

Nitrosamines are a class of mutagenic substances that can display high carcinogenic potential. New chemical entities may have the potential to form unique nitrosamines specific to the drug substance. It is therefore essential to understand the gas-phase fragmentation behavior of nitrosamine compounds to enable the development of analytical methods to characterize novel nitrosamine compounds.

METHODS

The gas-phase fragmentation behavior of eight model nitrosamine compounds representing the common substructures seen in many small molecule pharmaceutical compounds was studied with positive electrospray ionization tandem mass spectrometry (ESI-MS/MS). The fragmentation patterns of these compounds under various collision parameters available in commercially available mass spectrometers were studied.

RESULTS

Protonated nitrosamine compounds produced diagnostic fragment ions upon MS/MS. Three primary structure-dependent fragmentation pathways were observed. The first pathway involves the loss of 30 Da which corresponds to the loss of the NO radical from the protonated nitrosamine compound (Group 1). The second and third fragmentation pathways, which have not been reported for nitrosamine compounds, proceed via the loss of H₂ O from the protonated nitrosamine compound (Group 2), and elimination and a loss of 46 Da (loss of NH₂ NO) from the nitrosamine compound (Group 3).

CONCLUSIONS

Results presented in this work provide an overview of the gas-phase fragmentation patterns of nitrosamine compounds and may be useful in identifying novel nitrosamine compounds in complex matrices.

Nitric Oxide Delivering Surfaces: An Overview of Functionalization Strategies and Efficiency Progress

An overview on the design of nitric oxide (NO) delivering surfaces for biomedical purposes is provided, with a focus on the advances of the past 5 years. A localized supply of NO is of a particular interest due to the pleiotropic biological effects of this diatomic compound. Depending on the generated NO flux, the surface can mimic a physiological release profile to provide an activity on the vascular endothelium or an antibacterial activity. Three requirements are considered to describe the various strategies leading to a surface delivering NO. Firstly, the coating must be selected in accordance with the properties of the substrate (nature, shape, dimensions…). Secondly, the releasing and/or generating kinetics of NO should match the targeted biological application. Currently, the most promising structures are developed to provide an adaptable NO supply driven by pathophysiological needs. Finally, the biocompatibility and the stability of the surface must also be considered regarding the expected residence time of the device. A critical point of view is proposed to help readers in the design of the NO delivering surface according to its expected requirement and therapeutic purpose.

Practical and Science-Based Strategy for Establishing Acceptable Intakes for Drug Product N-Nitrosamine Impurities

The potential for N-nitrosamine impurities in pharmaceutical products presents a challenge for the quality management of medicinal products. N-Nitrosamines are considered cohort-of-concern compounds due to the potent carcinogenicity of many of the structurally simple chemicals within this structural class. In the past 2 years, a number of drug products containing certain active pharmaceutical ingredients have been withdrawn or recalled from the market due to the presence of carcinogenic low-molecular-weight N,N-dialkylnitrosamine impurities. Regulatory authorities have issued guidance to market authorization holders to review all commercial drug substances/products for the potential risk of N-nitrosamine impurities, and in cases where a significant risk of N-nitrosamine impurity is identified, analytical confirmatory testing is required. A key factor to consider prior to analytical testing is the estimation of the daily acceptable intake (AI) of the N-nitrosamine impurity. A significant proportion of N-nitrosamine drug product impurities are unique/complex structures for which the development of low-level analytical methods is challenging. Moreover, these unique/complex impurities may be less potent carcinogens compared to simple nitrosamines. In the present work, our objective was to derive AIs for a large number of complex N-nitrosamines without carcinogenicity data that were identified as potential low-level impurities. The impurities were first cataloged and grouped according to common structural features, with a total of 13 groups defined with distinct structural features. Subsequently, carcinogenicity data were reviewed for structurally related N-nitrosamines relevant to each of the 13 structural groups and group AIs were derived conservatively based on the most potent N-nitrosamine within each group. The 13 structural group AIs were used as the basis for assigning AIs to each of the structurally related complex N-nitrosamine impurities. The AIs of several N-nitrosamine groups were found to be considerably higher than those for the simple N,N-dialkylnitrosamines, which translates to commensurately higher analytical method detection limits.

Trace Level Quantification of 4-Methyl-1-nitrosopiperazin in Rifampicin Capsules by LC-MS/MS

Rifampicin is a first-line anti-tuberculosis drug. However, in August 2020, the presence of 1-methyl-4-nitrosopiperazine (MNP), a nitrosamine impurity, was detected by the United Stated Food and Drug Administration (US FDA) in rifampicin capsules. Consequently, the development of efficient methods for the detection of MNP is an important objective. In this study, the MNP present in rifampicin capsules was detected using LC-MS/MS. A total of 27 batches from nine manufacturers in the Chinese market were tested, with MNP (0.33–2.36 ppm) being detected in all samples at levels exceeding the maximum acceptable intake limit of 0.16 ppm initially set by the FDA. However, after considering the associated benefits and risks, the FDA-approved limit was revised to 5 ppm; hence, all the samples examined herein exhibited MNP levels well below the required limit. Furthermore, the results of forced degradation experiments suggest that MNP is formed by the thermal degradation of rifampicin.

Estimated Cancer Risks Associated with Nitrosamine Contamination in Commonly Used Medications

Many nitrosamines are potent carcinogens, with more than 30 listed under California's Proposition 65. Recently, nitrosamine contamination of commonly used drugs for treatment of hypertension, heartburn, and type 2 diabetes has prompted numerous Food and Drug Administration (FDA) recalls in the US. These contaminants include the carcinogens NDMA (N-nitrosodimethylamine) and NDEA (N-nitrosodiethylamine) and the animal tumorigen NMBA (N-nitroso-N-methyl-4-aminobutyric acid). NMBA and NDEA are metabolically and/or structurally related to NDMA, an N-nitrosomethyl-n-alkylamine (NMA), and 12 other carcinogenic NMAs. These nitrosamines exhibit common genotoxic and tumorigenic activities, with shared target tumor sites amongst chemicals and within a given laboratory animal species. We use the drug valsartan as a case study to estimate the additional cancer risks associated with NDMA and NDEA contamination, based on nitrosamine levels reported by the US FDA, cancer potencies developed by California's Proposition 65 program and the US Environmental Protection Agency (EPA), and specific exposure scenarios. These estimates suggest that nitrosamine contamination in drugs that are used long-term can increase cancer risks and pose a serious concern to public health.

New 1H-benzimidazole-2-yl hydrazones with combined antiparasitic and antioxidant activity

Parasitic infections, caused mainly by the species Trichinella spiralis (T. spiralis), are widespread around the world and lead to morbidity and mortality in the population. Meanwhile, some studies have showed that these parasites induce oxidative stress in the infected host. With the aim of developing a class of compounds combining anthelmintic with antioxidant properties, a series of new benzimidazolyl-2-hydrazones 5a-l, bearing hydroxyl- and methoxy-groups, were synthesized. The anthelmintic activity on encapsulated T. spiralis was studied in vitro thus indicating that all hydrazones were more active than the clinically used anthelmintic drugs albendazole and ivermectin. 5b and 5d killed the total parasitic larvae (100% effectiveness) after 24 hours incubation period at 37 °C in both concentrations (50 and 100 μg ml⁻¹). The antioxidant activity of the target compounds was elucidated in vitro against stable free radicals DPPH and ABTS as well as iron induced oxidative damage in model systems containing biologically relevant molecules lecithin and deoxyribose. The two 2,3- and 3,4-dihydroxy hydrazones 5b and 5d were the most effective radical scavengers in all studied systems. DFT calculations were applied to calculate the reaction enthalpies in polar and nonpolar medium and estimate the preferred mechanism of antioxidant activity. The relative radical scavenging ability of compounds 5a-l showed a good correlation to the experimentally observed trends. It was found that the studied compounds are capable to react with various free radicals – ˙OCH₃, ˙OOH and ˙OOCH₃, through several possible reaction pathways – HAT in nonpolar medium, SPLET in polar medium and RAF in both media.

The design of new drug candidates that combine anthelmintic and antioxidant actions in one molecule offers a beneficial approach in the treatment of the tissue damages, immune system dysfunction and oxidative stress caused by trichinellosis.