Simultaneous determination of formic acid and formaldehyde in pharmaceutical excipients using headspace GC/MS

Investigation of the Formaldehyde-Catalyzed NNitrosation of Dialkyl Amines: An Automated Experimental and Kinetic Modelling Study Using Dibutylamine

The potential for drug substances and drug products to contain low levels of N-nitrosamines is of continued interest to the pharmaceutical industry and regulatory authorities. Acid-promoted nitrosation mechanisms in solution have been investigated widely in the literature and are supported by kinetic modelling studies. Carbonyl compounds, particularly formaldehyde, which may be present as impurities in excipients and drug product packaging components or introduced during drug substance manufacturing processes are also known to catalyze nitrosation, but their impact on the risk of N-nitrosamine formation has not been systematically investigated to date. In this study, we experimentally investigated the multivariate impact of formaldehyde, nitrite and pH on N-nitrosation in aqueous solution using dibutylamine as a model amine. We augmented a published kinetic model by adding formaldehyde-catalyzed nitrosation reactions. We validated the new kinetic model vs. the experimental data and then used the model to systematically investigate the impact of formaldehyde levels on N-nitrosamine formation. Simulations of aqueous solution systems show that at low formaldehyde levels the formaldehyde-catalyzed mechanisms are insignificant in comparison to other routes. However, formaldehyde-catalyzed mechanisms can become more significant at neutral and high pH under higher formaldehyde levels. Model-based sensitivity analysis demonstrated that under high nitrite levels and low formaldehyde levels (where the rate of formaldehyde-catalyzed nitrosation is low compared to the acid-promoted pathways) the model can be used with kinetic parameters for model amines in the literature without performing additional experiments to fit amine-specific parameters. For other combinations of reaction parameters containing formaldehyde, the formaldehyde-catalyzed kinetics are non-negligible, and thus it is advised that, under such conditions, additional experiments should be conducted to reliably use the model.

Influence of Cuticular Waxes from Triticale on Rumen Fermentation: A Metabolomic and Microbiome Profiling Study

Cuticular wax, a critical defense layer for plants, remains a relatively unexplored factor in rumen fermentation. We investigated the impact of cuticular wax on rumen fermentation using triticale as a model. In total, six wax classes were identified, including fatty acids, aldehydes, alkane, primary alcohol, alkyresorcinol, and β-diketone, with low-bloom lines predominated by 46.05% of primary alcohols and high-bloom lines by 35.64% of β-diketone. Low-wax addition (2.5 g/kg DM) increased the gas production by 19.25% (P < 0.05) and total volatile fatty acids by 6.34% (P > 0.05), and enriched key carbohydrate-fermenting rumen microbes like Saccharofermentans, Ruminococcus, and Prevotellaceae, when compared to non-wax groups. Metabolites linked to nucleotide metabolism, purine metabolism, and protein/fat digestion in the rumen showed a positive correlation with low-wax, benefiting rumen microbes. This study highlights the intricate interplay among cuticular wax, rumen microbiota, fermentation, and metabolomics in forage digestion, providing insights into livestock nutrition and forage utilization.

Impact of formaldehyde, acetaldehyde, and N-(3-(Dimethylamino)propyl)methacrylamide on the efficacy of the human derived coagulation factor IX

Polymer-borne leachables such as formaldehyde, acetaldehyde, and N-3-(Dimethylamino)propyl)methacrylamide (DMAPMA) may interact with therapeutic proteins. In this study, the leachables were spiked into human derived coagulation factor IX (FIX) at concentrations of 1, 10, 50, 100, and 500 µg/mL, corresponding to a leachable - FIX ratio of 0.5, 5, 25, 50 and 250 %, respectively. The spiked samples were visually inspected, and pH was measured. No visual effects were observed, and pH was within the drug product's specified range. Recovery experiments were performed and no loss of leachables was identified. Protein structure analysis revealed that formaldehyde reacted with lysine contained in two different positions of FIX, in a concentration-dependent manner starting at 10 µg/mL (5 %). The clotting activity of FIX was measured. The activity of the samples spiked with 500 µg/mL (250 %) of formaldehyde dropped by more than half. The activity of the samples spiked with acetaldehyde began to drop at 50 µg/mL (25 %) and continued to decline in concentration-dependent manner. DMAPMA did not impair the activity of FIX. The findings conclude that depending on the concentration, some leachables may react with or modify therapeutic proteins, potentially causing an undesired pharmacological effect however, this is specific to each protein.

Highly Sensitive and Selective Formaldehyde Gas Sensors Based on Polyvinylpyrrolidone/Nitrogen-Doped Double-Walled Carbon Nanotubes

A highly sensitive and selective formaldehyde sensor was successfully fabricated using hybrid materials of nitrogen-doped double-walled carbon nanotubes (N-DWCNTs) and polyvinylpyrrolidone (PVP). Double-walled carbon nanotubes (DWCNTs) and N-DWCNTs were produced by high-vacuum chemical vapor deposition using ethanol and benzylamine, respectively. Purified DWCNTs and N-DWCNTs were dropped separately onto the sensing substrate. PVP was then dropped onto pre-dropped DWCNT and N-DWCNTs (hereafter referred to as PVP/DWCNTs and PVP/N-DWCNTs, respectively). As-fabricated sensors were used to find 1,2-dichloroethane, dichloromethane, formaldehyde and toluene vapors in parts per million (ppm) at room temperature for detection measurement. The sensor response of N-DWCNTs, PVP/DWCNTs and PVP/N-DWCNTs sensors show a high response to formaldehyde but a low response to 1,2-dichloroethane, dichloromethane and toluene. Remarkably, PVP/N-DWCNTs sensors respond sensitively and selectively towards formaldehyde vapor, which is 15 times higher than when using DWCNTs sensors. This improvement could be attributed to the synergistic effect of the polymer swelling and nitrogen-sites in the N-DWCNTs. The limit of detection (LOD) of PVP/N-DWCNTs was 15 ppm, which is 34-fold higher than when using DWCNTs with a LOD of 506 ppm. This study demonstrated the high sensitivity and selectivity for formaldehyde-sensing applications of high-performance PVP/N-DWCNTs hybrid materials.

Trace Aldehydes in Solid Oral Dosage Forms as Catalysts for Nitrosating Secondary Amines

Nitrosamine impurities may form during drug substance manufacturing processes. Here, we focus on nitrosamine impurity level growth in oral drug products during long term stability studies. Nitrosamine growth mechanisms in oral dosage forms are typically framed as due to nitrosating agents that can be formed in solutions of nitrous acid with a required pH value of around pH 5 or below. We strive in this work to bring awareness to pharmaceutical scientists that formaldehyde, common in oral dosage form excipients, has previously been shown in solution to catalyze the reaction between secondary amines and nitrite ion to give nitrosamine products. This mechanism operates at pH ∼6 and higher. We attempt to re-frame the solution work as relevant to pharmaceutical solid dosage forms. Recent examples of solid dosage form product recalls are used to demonstrate the formaldehyde catalyzed nitrosation pathway operating in the solid state.

Novel Method of Analysis for the Determination of Residual Formaldehyde by High-Performance Liquid Chromatography

Formaldehyde is commonly used as an alkylating agent in the pharmaceutical industry. Consequently, its residual level in drug substances and/or their intermediates needs to be accurately quantified. Formaldehyde is a small, volatile molecule with a weak chromophore (the carbonyl group), and its direct analysis by GC-FID and HPLC-UV is difficult. For these reasons, the majority of papers found in the literature are based upon a derivatisation process (most commonly using the desensitised explosive 2,4-dinitrophenylhydrazine) prior to the analysis of formaldehyde. A novel high-performance liquid chromatography (HPLC) method with UV detection for its quantification in a pharmaceutical is described in this paper. The method proposed herein is based upon a derivatisation reaction between formaldehyde and 4-methylbenzenesulfonohydrazide (MBSH) before analysis by HPLC-UV. Selectivity, linearity, limit of quantification, accuracy, repeatability, intermediate precision, and solution stability were successfully assessed as per ICH guideline Q2(R1), and the method has also been validated in a good manufacturing practice (GMP) laboratory in the UK.

Oxidative Stability in Lipid Formulations: a Review of the Mechanisms, Drivers, and Inhibitors of Oxidation

The importance of lipid-based formulations in addressing solubility and ultimately the bioavailability issues of the emerging drug entities is undeniable. Yet, there is scarcity of literature on lipid excipient chemistry and performance, notably in relation to oxidative stability. While not all lipid excipients are prone to oxidation, those with sensitive moieties offer drug delivery solutions that outweigh the manageable oxidative challenges they may present. For example, caprylocaproyl polyoxylglycerides help solubilize and deliver cancer drug to patients, lauroyl polyoxylglycerides enhance the delivery of cholesterol lowering drug, and sesame/soybean oils are critical part of parenteral nutrition. Ironically, excipients with far greater oxidative propensity are omnipresent in pharmaceutical products, a testament to the manageability of oxidative challenges in drug development. Successful formulation development requires awareness of what, where, and how formulation stability may be impacted, and accordingly taking appropriate steps to circumvent or meet the challenges ahead. Aiming to fill the information gap from a drug delivery scientist perspective, this review discusses oxidation pathways, prooxidants, antioxidants, and their complex interplay, which can paradoxically take opposite directions depending on the drug delivery system.

Isolation, Identification and Structural Verification of a Methylene-Bridged Naloxone "Dimer" Formed by Formaldehyde

We report the isolation and characterization of a methylene bridged "dimer" of the opioid antagonist Naloxone, previously detected in experimental Buprenorphine-Naloxone oral films. This compound was found to form via an aldol addition followed by a condensation reaction under acidic conditions between two units of Naloxone and one unit of formaldehyde. HPLC-UV-HRMS analysis revealed the formation of three individual stereoisomers during this reaction, which were separately isolated using solid-phase extraction. These isomers were shown to freely react into one another in solvent, forming an equilibrium. The structure of the unknown compound was determined via HRMS spectrometry and 1D and 2D NMR spectroscopy.

Analytical Method Development for Determining Formaldehyde in Cream Cosmetics Using Hyphenated Gas Chromatography

Formaldehyde has been reported to be a potential human carcinogen due to its toxicity. However, formaldehyde releaser substances are still widely used as a preservative in cosmetics. Researchers have developed various methods for determining formaldehyde. One of the problems involved in the standard method is that of obtaining a derivatization agent, especially for routine analysis in the National Agency of Drug and Food, Indonesia. Therefore, this study aimed to develop a new method using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID). The significant modifications involved optimizations of five series of concentrations of p-toluenesulfonic (PTS) acid in ethanol (acidified ethanol), used as the derivatization agent, and the conditions of time and temperature of the reaction to yield the highest peak area. In addition, sample analysis was also carried out using the 2,4-dinitrophenylhydrazine (DNPH) method with high-performance liquid chromatography (HPLC) to compare the quantification results. The validated method showed intraday and interday precision, an accuracy (% RSD) of less than 3.7%, confidence interval 95.0-105.0%, a limit of detection and quantitation of 0.0099 and 0.0329 μg/mL (for DNPH by HPLC-DAD), 0.0158 and 0.0528 μg/mL (for PTS by SHS-GC-MS), and 1.1287 and 3.7625 μg/mL (for PTS liquid by GC-FID), respectively. These results have met the requirements for a validated analytical method and could be applied for routine analysis.

Shorter and Rugged Analytical GC Method for Residual Solvents Content in Active Pharmaceutical Ingredient

This work describes the highly selective and sensitive robust analytical method (gas chromatography) for the qualitative and quantitative analysis of commonly used residual solvents (like methanol, ethanol, acetonitrile, dichloromethane, methyl tert-butyl ether, n-hexane, 1-propanol, ethyl acetate, tetrahydrofuran, N,N-diisopropylethylamine (DIPEA) and dimethylformamide), in an active pharmaceuticals ingredients. The developed method was optimized with good resolution (>1.9 between close eluting solvents) and a shorter run time (20 min). All the solvents were separated using GC column DB-624, 30-m length, 0.32-mm diameter, 1.8-μm particle size, nitrogen as a carrier gas and recorded the signals using flame ionization detector (FID). Further, analytical method validation has been performed for the developed analytical method and the validation results demonstrated its routine application for the determination of residual solvents content by GC-head space (HS). The practical application was demonstrated by the suitable API batch analysis (having sample Con. 40 mg/mL). The present developed method has more advantages than the other methods for the qualitative and quantitative applications, such as shorter runtime, selective for multiple solvents (11 organic solvents) analysis at a time, highly sensitive at ppm levels. This GC-HS method could be used for the qualitative and quantitative determination of the residual solvents content in APIs.

Mass spectrometric and kinetics characterization of modified species of Growth Hormone Releasing Hexapeptide generated under thermal stress in different pH and buffers

Growth Hormone Releasing Peptide-6 (GHRP-6) is a promising molecule (H-His¹-d-Trp- Ala-Trp-d-Phe-Lys⁶-NH₂) for the treatment of several diseases. Studies on the degradation pathways of this molecule under stressed conditions are needed to develop appropriate formulations. Degradation products (DPs) of GHRP-6, generated by heating in the dark at 60 °C with pH ranging from 3.0 to 8.0 and in presence of common buffers, were isolated by RP-HPLC and characterized by ESI-MS/MS. C-terminal deamidation of GHRP-6 was generated preferentially at pH 3.0 and 8.0. Hydrolysis and head-to-tail cyclization were favored at pH ranging from 6.0 to 7.0 in phosphate containing buffers. A DP with +12 Da molecular mass was presumably originated by the reaction with formaldehyde derived from some of the additives and/or elastomeric closures. Certain DPs derived from the acylation reaction of the tri- and di-carboxylic buffering species were favored at pH 3.0-6.0 and indicate that buffer components, including those "Generally Recognized as Safe", may potentially introduce chemical modifications and product heterogeneity. Nano LC-MS/MS analysis revealed GHRP-6 was also detected as a low-abundance species with Trp oxidized to 5-hydroxy, kynurenine, and N-formylkynurenine. The kinetics for the formation of the major degradation products was also studied by RP-HPLC.

Formation of a Thiol-Ene Addition Product of Asthma Medication Montelukast Caused by a Widespread Tin-Based Thermal Stabilizer

We report the formation and characterization of two diastereomeric thiol-ene addition products of the asthma medication Montelukast within chewing tablets. Widespread tin-based thermal stabilizers dioctyltin bis(2-ethylhexyl thioglycolate) and monooctyltin tris(2-ethylhexyl thioglycolate), used in the manufacturing process of the medication's forming foil, were identified as the source of the thiol reactant, showing that these stabilizers may play a part in the degradation of Montelukast and APIs with functionalities similar to those of Montelukast, which should be considered during development of medication. The isolation and analysis of these impurities was performed by HPLC and UV-vis spectroscopy. HRMS and NMR data were collected to characterize and determine the structures of these compounds.

Formation of formaldehyde as an artifact peak in head space GC analysis resulting from decomposition of sample diluent DMSO: A GC-MS investigation with deuterated DMSO

During our method development for residual formaldehyde detection in a drug substance, unusually high levels of formaldehyde were detected when using a mixed solvent of EtOH/DMSO (4:1, v/v) as sample diluent in headspace GC analysis (HS-GC). Initial investigation found that formaldehyde is used in the preparation for one of the starting materials of the drug substance. Nevertheless, there is neither other source of formaldehyde in the manufacturing process of the drug substance, nor would formaldehyde be generated during the process. In the ensuing root cause investigation, it was found that once the solvent DMSO is replaced by other solvent [e.g., N,N-dimethylformamide (DMF)], while keeping other method parameters unchanged in the HS-GC analysis, the level of formaldehyde in the same batch of the drug substance became undetectable (LOD: 3 ppm). All the evidence suggested that the observed formaldehyde in the HS-GC analysis might be due to the decomposition of DMSO, which could be facilitated by the presence of this particular drug substance. In other words, the presence of the drug substance (in the form of HCl salt) would cause a minor decomposition of DMSO to produce formaldehyde. To prove this hypothesis, a GC-MS experiment of the drug substance was conducted in which deuterated DMSO (DMSO-_d6) was used in place of regular DMSO; the expected deuterated derivatization product, i.e., diethoxymethane-_d2 (C₂H₅OCD₂OC₂H₅), was observed in the HS-GC-MS analysis. Therefore, it became clear that this drug substance facilitates the minor decomposition of DMSO in the HS-GC analysis. In such a case, formaldehyde is an artifact peak, or ghost peak, rather than a true impurity of the drug substance. The false positive results of formaldehyde were also found in other four compounds (three drug substances and one reagent) which are all in the form of HCl or HBr salts, suggesting that generation of formaldehyde from DMSO could be a widely occurred phenomenon in HS-GC analysis of alkyl amines in the form of HCl or HBr salts, when DMSO-containing diluents are used during sample preparation.

Structure elucidation and formation mechanistic study of a methylene-bridged pregabalin dimeric degradant in pregabalin extended-release tablets

During the pharmaceutical development of pregabalin extended-release tablets, an unknown degradant at a relative retention time (RRT) of 11.7 was observed and its nominal amount exceeded the ICH identification threshold in an accelerated stability study. The aim of this study is to identify the structure and investigate the formation mechanism of this impurity for the purpose of developing a chemically stable pharmaceutical product. By utilizing multi-stage LC-MS analysis in conjunction with mechanism-based stress study, the structure of the RRT 11.7 impurity was rapidly identified as a dimeric degradant that is caused by dimerization of two pregabalin molecules with a methylene bridging the two pregabalin moieties. The structure of the dimer was confirmed by 1D and 2D NMR measurement. The formation pathway of the dimeric degradant was also inferred from the mechanism-based stress study, which implicated that the bridging methylene could originate from formaldehyde which might be the culprit that triggers the dimerization in the first place. The subsequent API-excipients compatibility study indicated that the degradant was indeed formed in the compatibility experiments between pregabalin API and two polymeric excipients (PEO and PVPP) that are known to contain residual formaldehyde, but only in the co-presence of another excipient, colloidal silicon dioxide (SiO₂). The kinetic behavior of the degradant formation was also investigated and two kinetic models were utilized based on the Arrhenius and Eyring equations, respectively, to calculate the activation energy (E_a) as well as the enthalpy of activation (△H^‡), entropy of activation (△S^‡), and Gibbs free energy (△G^‡) of the degradation reaction. The results of this study would be useful for the understanding of similar dimeric degradant formation in finished products of drug substances containing primary or secondary amine moieties.

Molecular cobalt corrole complex for the heterogeneous electrocatalytic reduction of carbon dioxide

Electrochemical conversion of CO2 to alcohols is one of the most challenging methods of conversion and storage of electrical energy in the form of high-energy fuels. The challenge lies in the catalyst design to enable its real-life implementation. Herein, we demonstrate the synthesis and characterization of a cobalt(III) triphenylphosphine corrole complex, which contains three polyethylene glycol residues attached at the meso-phenyl groups. Electron-donation and therefore reduction of the cobalt from cobalt(III) to cobalt(I) is accompanied by removal of the axial ligand, thus resulting in a square-planar cobalt(I) complex. The cobalt(I) as an electron-rich supernucleophilic d8-configurated metal centre, where two electrons occupy and fill up the antibonding dz2 orbital. This orbital possesses high affinity towards electrophiles, allowing for such electronically configurated metals reactions with carbon dioxide. Herein, we report the potential dependent heterogeneous electroreduction of CO2 to ethanol or methanol of an immobilized cobalt A3-corrole catalyst system. In moderately acidic aqueous medium (pH = 6.0), the cobalt corrole modified carbon paper electrode exhibits a Faradaic Efficiency (FE%) of 48 % towards ethanol production.

Conductomeric Evaluation of the Release Kinetics of Active Substances from Pharmaceutical Preparations Containing Iron Ions

The aim of this study was to verify the effect of the formulation on the release kinetics of active substances from preparations containing iron ions using in-line conductivity measurements. A simple, fast method was developed and may be applied for detailed evaluation of some kinetics factors obtained from the release data. Four different equations were used: zero-order equation, first-order equation, models: Korsmeyer–Peppas and Hixson–Crowell. Values of the determined half-time release for zero and first-order kinetic models ranged from 11.56 to 89.97 min. In the case of analysis according to these typical models, the values of the square root of the correlation coefficients were included between 0.9916 and 0.9995. The results transformed for the Hixson–Crowell model as constant release Ks, ranged between 0.0160 and 0.0437. The values of the respective calculated squares of the correlation coefficient ranged from 0.9933 to 0.9959. The determined release rate constants according to the Korsmeyer–Peppas model were between 0.0023 and 0.1630. The coefficients ‘n’ of the Korsmeyer–Peppas equation did not exceed 1.2 with the corresponding r² values 0.9408–0.9960. Obtained results confirmed that the method is applicable for evaluation of selected drug compositions containing iron ions.

Lab-simulated downhole leaching of formaldehyde from proppants by high performance liquid chromatography (HPLC), headspace gas chromatography-vacuum ultraviolet (HS-GC-VUV) spectroscopy, and headspace gas chromatography-mass spectrometry (HS-GC-MS)

The ability of different methods to analyze formaldehyde and other leachates from proppants was investigated under lab-simulated downhole conditions. These methods include high performance liquid chromatography (HPLC), headspace gas chromatography-vacuum ultraviolet spectroscopy (HS-GC-VUV), and headspace gas chromatography-mass spectrometry (HS-GC-MS). Two different types of resin-coated proppants, phenol-formaldehyde- and polyurethane-based, were examined. Each proppant was tested at different time intervals (1, 4, 15, 20, or 25 hours) to determine the timeframe for chemical dissolution. Analyses were performed at room temperature and heated (93 °C) to examine how temperature affected the concentration of leachates. Multiple matrices were examined to mimic conditions in subsurface environment including deionized water, a solution surrogate to mimic the ionic concentration of produced water, and recovered produced water. The complexity of these samples was further enhanced to simulate downhole conditions by the addition of shale core. The influence of matrix components on the analysis of formaldehyde was greatly correlated to the quantity of formaldehyde measured. Of the three techniques surveyed, HS-GC-MS was found to be better suited for the analysis of formaldehyde leachates in complex samples. It was found that phenol-formaldehyde resin coated proppants leached higher concentrations of formaldehyde than the polyurethane resin coated proppants.

A Robust Static Headspace GC-FID Method to Detect and Quantify Formaldehyde Impurity in Pharmaceutical Excipients

Formaldehyde is a highly reactive impurity that can be found in many pharmaceutical excipients. Trace levels of this impurity may affect drug product stability, safety, efficacy, and performance. A static headspace gas chromatographic method was developed and validated to determine formaldehyde in pharmaceutical excipients after an effective derivatization procedure using acidified ethanol. Diethoxymethane, the derivative of formaldehyde, was then directly analyzed by GC-FID. Despite the simplicity of the developed method, however, it is characterized by its specificity, accuracy, and precision. The limits of detection and quantification of formaldehyde in the samples were of 2.44 and 8.12 µg/g, respectively. This method is characterized by using simple and economic GC-FID technique instead of MS detection, and it is successfully used to analyze formaldehyde in commonly used pharmaceutical excipients.

Simultaneous measurement of formic acid, methanol and ethanol in vitreous and blood samples of postmortem by headspace GC-FID

Background

Formic acid (formate) is the main reason for toxicity and death through methanol poisoning. The simultaneous determination of methanol, ethanol, and formate in the body can help to discover the cause of death and is useful in the diagnosis of acute methanol poisoning. The measurement of formate is not yet available in Iran. With regard to the increasing rate of methanol poisoning and its related mortality in Iran, as well as the main role of formate in methanol poisoning, this study was designed to set up an analytical method for the concurrent determination of ethanol, methanol, and formate.

Methods

Following the modification of a previously developed gas chromatography method, vitreous and blood samples of 43 postmortem cases with a history of methanol intoxication were collected over a period of 2 years at the Legal Medicine Organization of Mashhad. Thereafter, ethanol, methanol, and formate concentrations were measured by headspace GC/FID. Formate esterification was performed by the methylation of formate with sulfuric acid and methanol. In order to confirm the esterification method for the production of methyl formate, we used gas chromatography with a mass detector (GC/MS) because of its higher sensitivity and accuracy. Furthermore, the correlations between formate and methanol concentrations in blood and vitreous samples, and between formate and methanol were investigated.

Results

A significant relationship was found only between methanol concentrations in blood and vitreous samples (P < 0.03).

Conclusions

In postmortems, with the passage of time since alcohol ingestion, the measurement of only methanol concentration cannot determine the degree of toxicity or the cause of death. Therefore, using the present analytical method and measurement of formic acid, we can estimate the degree of toxicity and cause of death.

Effect of surfactants and hydrophilic polymers on the stability of an antihypertensive drug candesartan cilexetil: Evaluation by HPLC

OBJECTIVES

The objective of this study is to investigate the effect of surfactants (polysorbate 80 and sodium lauryl sulphate) and hydrophilic polymers (polyvinylpyrrolidone and polyethylene glycol 6000) on the stability of candesartan cilexetil under isothermal stress conditions (100°C, 48h).

METHODS

HPLC method was employed to evaluate the drug content and formation of degradation products in stress samples. Drug and degradation products were separated on Hypersil BDS C18 (250×4.6mm, 5μ) column using acetonitrile-water (pH 2.8) in the ratio of 85:15% v/v as a mobile phase.

RESULT

Similar degradation behaviour of drug was observed with polyvinylpyrrolidone, polyethylene glycol 6000 and polysorbate 80; four common degradation peaks were observed at the retention time of 3.7, 4.5, 7.8 and 11minutes. One extra common degradation peak of very low intensity was also observed with polyethylene glycol 6000 and polysorbate 80 at the retention time of 4.2min. The drug was eluting at the retention time of 5.4min. In the case of sodium lauryl sulphate, two prominent degradation peaks were observed at the retention time of 3.7 and 13.25min along with few very low-intensity degradation peaks.

CONCLUSION

The drug showed 41%, 64%, 72% and 98% degradation in presence of polyvinylpyrrolidone, polyethylene glycol 6000, polysorbate 80 and sodium lauryl sulphate, respectively.

Metabolomic signature of brain cancer

Despite advances in surgery and adjuvant therapy, brain tumors represent one of the leading causes of cancer-related mortality and morbidity in both adults and children. Gliomas constitute about 60% of all cerebral tumors, showing varying degrees of malignancy. They are difficult to treat due to dismal prognosis and limited therapeutics. Metabolomics is the untargeted and targeted analyses of endogenous and exogenous small molecules, which charact erizes the phenotype of an individual. This emerging "omics" science provides functional readouts of cellular activity that contribute greatly to the understanding of cancer biology including brain tumor biology. Metabolites are highly informative as a direct signature of biochemical activity; therefore, metabolite profiling has become a promising approach for clinical diagnostics and prognostics. The metabolic alterations are well-recognized as one of the key hallmarks in monitoring disease progression, therapy, and revealing new molecular targets for effective therapeutic intervention. Taking advantage of the latest high-throughput analytical technologies, that is, nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS), metabolomics is now a promising field for precision medicine and drug discovery. In the present report, we review the application of metabolomics and in vivo metabolic profiling in the context of adult gliomas and paediatric brain tumors. Analytical platforms such as high-resolution (HR) NMR, in vivo magnetic resonance spectroscopic imaging and high- and low-resolution MS are discussed. Moreover, the relevance of metabolic studies in the development of new therapeutic strategies for treatment of gliomas are reviewed.

Mechanistic Studies of the N-formylation of Edivoxetine, a Secondary Amine-Containing Drug, in a Solid Oral Dosage Form

Edivoxetine (LY2216684 HCl), although a chemically stable drug substance, has shown the tendency to degrade in the presence of carbohydrates that are commonly used tablet excipients, especially at high excipient:drug ratios. The major degradation product has been identified as N-formyl edivoxetine. Experimental evidence including solution and solid-state investigations, is consistent with the N-formylation degradation pathway resulting from a direct reaction of edivoxetine with (1) formic acid (generated from decomposition of microcrystalline cellulose or residual glucose) and (2) the reducing sugar ends (aldehydic carbons) of either residual glucose or the microcrystalline cellulose polymer. Results of labeling experiments indicate that the primary source of the formyl group is the C1 position from reducing sugars. Presence of water or moisture accelerates this degradation pathway. Investigations in solid and solution states support that the glucose Amadori Rearrangement Product does not appear to be a direct intermediate leading to N-formyl degradation of edivoxetine, and oxygen does not appear to play a significant role. Solution-phase studies, developed to rapidly assess propensity of amines toward Maillard reactivity and formylation, were extended to show comparative behavior with example systems. The cyclic amine systems, such as edivoxetine, showed the highest propensity toward these side reactions.

Use of Activated Carbon in Packaging to Attenuate Formaldehyde-Induced and Formic Acid-Induced Degradation and Reduce Gelatin Cross-Linking in Solid Dosage Forms

Formaldehyde and formic acid are reactive impurities found in commonly used excipients and can be responsible for limiting drug product shelf-life. Described here is the use of activated carbon in drug product packaging to attenuate formaldehyde-induced and formic acid-induced drug degradation in tablets and cross-linking in hard gelatin capsules. Several pharmaceutical products with known or potential vulnerabilities to formaldehyde-induced or formic acid-induced degradation or gelatin cross-linking were subjected to accelerated stability challenges in the presence and absence of activated carbon. The effects of time and storage conditions were determined. For all of the products studied, activated carbon attenuated drug degradation or gelatin cross-linking. This novel use of activated carbon in pharmaceutical packaging may be useful for enhancing the chemical stability of drug products or the dissolution stability of gelatin-containing dosage forms and may allow for the 1) extension of a drug product's shelf-life when the limiting attribute is a degradation product induced by a reactive impurity, 2) marketing of a drug product in hotter and more humid climatic zones than currently supported without the use of activated carbon, and 3) enhanced dissolution stability of products that are vulnerable to gelatin cross-linking.

Surface acidity and solid-state compatibility of excipients with an acid-sensitive API: case study of atorvastatin calcium

The objectives of this study were to measure the apparent surface acidity of common excipients and to correlate the acidity with the chemical stability of an acid-sensitive active pharmaceutical ingredient (API) in binary API-excipient powder mixtures. The acidity of 26 solid excipients was determined by two methods, (i) by measuring the pH of their suspensions or solutions and (ii) the pH equivalent (pHeq) measured via ionization of probe molecules deposited on the surface of the excipients. The chemical stability of an API, atorvastatin calcium (AC), in mixtures with the excipients was evaluated by monitoring the appearance of an acid-induced degradant, atorvastatin lactone, under accelerated storage conditions. The extent of lactone formation in AC-excipient mixtures was presented as a function of either solution/suspension pH or pHeq. No lactone formation was observed in mixtures with excipients having pHeq > 6, while the lactone levels were pronounced (> 0.6% after 6 weeks at 50°C/20% RH) with excipients exhibiting pHeq < 3. The three pHeq regions (> 6, 3-6, and < 3) were consistent with the reported solution pH-stability profile of AC. In contrast to the pHeq scale, lactone formation did not show any clear trend when plotted as a function of the suspension/solution pH. Two mechanisms to explain the discrepancy between the suspension/solution pH and the chemical stability data were discussed. Acidic excipients, which are expected to be incompatible with an acid-sensitive API, were identified based on pHeq measurements. The incompatibility prediction was confirmed in the chemical stability tests using AC as an example of an acid-sensitive API.

Determination of trace amount of formaldehyde base on a bromate-Malachite Green system

A novel catalytic kinetic spectrophotometric method for determination of trace amount of formaldehyde (FA) has been established, based on catalytic effect of trace amount of FA on the oxidation of Malachite Green (MG) by potassium bromate in presence of sulfuric acid medium, and was reported for the first time. The method was monitored by measuring the decrease in absorbance of MG at 617 nm and allowed a precise determination of FA in the range of 0.003-0.08 μg mL(-1), with a limit of detection down to 1 ng mL(-1). The relative standard deviation of 10 replicate measurements was 1.63%. The method developed was approved to be sensitive, selective and accurate, and adopted to determinate free FA in samples directly with good accuracy and reproducibility.

Risk evaluation of impurities in topical excipients: The acetol case

Pharmaceutical excipients for topical use may contain impurities, which are often neglected from a toxicity qualification viewpoint. The possible impurities in the most frequently used topical excipients were evaluated in-silico for their toxicity hazard. Acetol, an impurity likely present in different topical pharmaceutical excipients such as propylene glycol and glycerol, was withheld for the evaluation of its health risk after dermal exposure.

An ex-vivo in-vitro permeation study using human skin in a Franz Diffusion Cell set-up and GC as quantification methodology showed a significant skin penetration with an overall K_p value of 1.82×10⁻³ cm/h. Using these data, limit specifications after application of a dermal pharmaceutical product were estimated. Based on the TTC approach of Cramer class I substances, i.e. 1800 µg/(day∙person), the toxicity-qualified specification limits of acetol in topical excipients were calculated to be 90 µg/mL and 180 µg/mL for propylene glycol and glycerol, respectively.

It is concluded that setting specification limits for impurities within a quality-by-design approach requires a case-by-case evaluation as demonstrated here with acetol.

The catalytic kinetic method for the determination of trace formaldehyde (FA) base on a bromate-eosin Y system

A new simple and highly sensitive catalytic kinetic method for the determination of trace amount of FA in food sample has been established. The method was based on the catalytic effect of FA on the oxidation of eosin Y by potassium bromate in present of phosphoric acid. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of eosin Y at 518 nm. Under the optimized experimental conditions, the developed method allowed the determination of FA in the range of 0.03-0.6 μg mL(-1) with a good precision, and the limit of detection was down to 0.00988 μg mL(-1). The relative standard deviation of five replicate measurements for the determination of FA in concentration 0.12 μg mL(-1) was 1.8%. The proposed method was successfully applied to the determination of FA in food directly and satisfactory results were obtained.

Self-microemulsifying drug delivery system (SMEDDS)--challenges and road ahead

Self-microemulsifying drug delivery system (SMEDDS) has emerged as a vital strategy to formulate poor water soluble compounds for bioavailability enhancement. However, certain limitations are associated with SMEDDS formulations which include in vivo drug precipitation, formulation handling issues, limited lymphatic uptake, lack of predictive in vitro tests and oxidation of unsaturated fatty acids. These limitations restrict their potential usage. Inclusion of polymers or precipitation inhibitors within lipid based formulations helps to maintain drug supersaturation after dispersion. This, thereby, improves the bioavailability and reduces the variability on exposure. Also, formulating solid SMEDDS helps to overcome liquid handling and stability problems. Usage of medium chain triglycerides (MCT) and suitable antioxidants to minimize oxidation of unsaturated fatty acids are few of the steps to overcome the limitations associated with SMEDDS. The review discussed here, in detail, the limitations of SMEDDS and suitable measures that can be taken to overcome them.

Stability of benzocaine formulated in commercial oral disintegrating tablet platforms

Pharmaceutical excipients contain reactive groups and impurities due to manufacturing processes that can cause decomposition of active drug compounds. The aim of this investigation was to determine if commercially available oral disintegrating tablet (ODT) platforms induce active pharmaceutical ingredient (API) degradation. Benzocaine was selected as the model API due to known degradation through ester and primary amino groups. Benzocaine was either compressed at a constant pressure, 20 kN, or at pressure necessary to produce a set hardness, i.e., where a series of tablets were produced at different compression forces until an average hardness of approximately 100 N was achieved. Tablets were then stored for 6 months under International Conference on Harmonization recommended conditions, 25°C and 60% relative humidity (RH), or under accelerated conditions, 40°C and 75% RH. Benzocaine degradation was monitored by liquid chromatography-mass spectrometry. Regardless of the ODT platform, no degradation of benzocaine was observed in tablets that were kept for 6 months at 25°C and 60% RH. After storage for 30 days under accelerated conditions, benzocaine degradation was observed in a single platform. Qualitative differences in ODT platform behavior were observed in physical appearance of the tablets after storage under different temperature and humidity conditions.