Oxidation of Drugs during Drug Product Development: Problems and Solutions

A comprehensive study of the colloidal properties, biocompatibility, and synergistic antioxidant actions of Antarctic krill phospholipids

Excipient selection is crucial to address the oxidation and solubility challenges of bioactive substances, impacting their safety and efficacy. AKPL, a novel ω-3 polyunsaturated fatty acids (PUFAs) esterified phospholipid derived from Antarctic krill, demonstrates unique antioxidant capabilities and synergistic effects. It exhibits pronounced surface activity and electronegativity at physiological pH, as evidenced by a critical micelle concentration (CMC) of 0.15 g/L and ζ-potential of -49.9 mV. In aqueous environments, AKPL self-assembles into liposomal structures, offering high biocompatibility and promoting cell proliferation. Its polyunsaturated bond-rich structure provides additional oxidation sites, imparting antioxidant properties superior to other phospholipids like DSPC and DOPC. Additionally, AKPL augments the efficacy of lipophilic antioxidants, such as alpha-tocopherol and curcumin, in aqueous media through both intermolecular and intramolecular interactions. In sum, AKPL emerges as an innovative unsaturated phospholipid, offering new strategies for encapsulating and delivering oxygen-sensitive agents.

Drug product formulation and fill/finish manufacturing process considerations for AAV-based genomic medicines

Adeno-associated viruses (AAVs) have become the delivery medium of choice for a variety of genomic medicine applications i.e., gene therapy, gene editing/regulation, and ex-vivo cell therapy. AAVs are protein-DNA complexes which have unique stability characteristics that are susceptible to various stress exposure conditions commonly seen in the drug product (DP) life cycle. This review takes a comprehensive look at AAV DP formulation and process development considerations that could impact critical quality attributes (CQAs) during manufacturing, packaging, shipping, and clinical use. Additional aspects related to AAV development reviewed herein are: (1) Different AAV serotypes with unique protein sequences and charge characteristics potentially leading to discrete stability profiles; (2) Manufacturing process challenges and optimization efforts to improve yield, recovery and purity especially during early development activities; and (3) Defining and identifying CQAs with analytical methods which are constantly evolving and present unique characterization challenges for AAV-based products.

Recent Advances in Material Technology for Leukemia Treatments

Leukemia is a widespread hematological malignancy characterized by an elevated white blood cell count in both the blood and the bone marrow. Despite notable advancements in leukemia intervention in the clinic, a large proportion of patients, especially acute leukemia patients, fail to achieve long-term remission or complete remission following treatment. Therefore, leukemia therapy necessitates optimization to meet the treatment requirements. In recent years, a multitude of materials have undergone rigorous study to serve as delivery vectors or direct intervention agents to bolster the effectiveness of leukemia therapy. These materials include liposomes, protein-based materials, polymeric materials, cell-derived materials, and inorganic materials. They possess unique characteristics and are applied in a broad array of therapeutic modalities, including chemotherapy, gene therapy, immunotherapy, radiotherapy, hematopoietic stem cell transplantation, and other evolving treatments. Here, an overview of these materials is presented, describing their physicochemical properties, their role in leukemia treatment, and the challenges they face in the context of clinical translation. This review inspires researchers to further develop various materials that can be used to augment the efficacy of multiple therapeutic modalities for novel applications in leukemia treatment.

Determination of trace elements in ibuprofen drug products using microwave-assisted acid digestion and inductively coupled plasma-mass spectrometry

Trace elements are found in most drugs as a result of the drug formulation and drug production methods. An inductively coupled plasma-mass spectrometry method for the determination of 24 trace elements (Mg, Ti, V, Cr, Mn, Cu, Fe, Co, Ni, Zn, As, Se, Mo, Ru, Rh, Pd, Ag, Cd, Sb, Ba, Ir, Pt, Au, and Pb) in solid ibuprofen tablets was established in relation to the ICH Q3D(R1) guideline, to evaluate the possibility of linking trace elemental profiles to drug formulation strategies, and to differentiate between drug products based on the trace elemental profiles. Ten European ibuprofen drug products were evaluated (n=3). The sample preparation was performed by microwave-assisted acid digestion using only 10 mg of homogenized sample and 900 μL of a mix of 65% HNO3, 37% HCl, and 30% H2O2. Solid residuals primarily composed of insoluble SiO2 excipients were removed by centrifugation. Only concentrations of Mg, Fe, Ti, Mn, Cr, and Ni were detected above the limits of detection and did not exceed the ICH Q3D(R1) guideline permitted daily exposure limits. The trace elemental profiles were evaluated through principal component analysis. Three principal components describing 96% of the variance were useful in grouping the ibuprofen drug products, and the detected trace elemental remnants could be related to drug formulation and drug production strategies. An in-house quality control material was used in lack of certified reference materials and was in combination with spike recoveries used for method validation. Good spike recoveries (94-119%) were obtained for all measured trace elements except Mg. Mg showed acceptable spike recoveries (75-155%) for mid and high-spike concentrations, but poor recoveries (30-223%) were detected with low spike concentrations in spike matrices containing high amounts of Mg. Overall, the method is suggested applicable for solid drugs containing insoluble SiO2 excipients and drugs comparable to ibuprofen.

Influence of Crystal Disorder on the Forced Oxidative Degradation of Vortioxetine HBr

The present study investigates the impact of the solid-state disorder of vortioxetine hydrobromide (HBr) on oxidative degradation under accelerated conditions. A range of solid-state disorders was generated via cryogenic ball milling. The solid-state properties were evaluated by calorimetry, infrared-, and Raman spectroscopies. While salt disproportionation occurred upon milling, no chemical degradation occurred by milling. The amorphous fraction remained physically intact under ambient storage conditions. Subsequently, samples with representative disordered fractions were mixed with a solid oxidative stressor (PVP-H2O2 complex) and were compressed to compacts. The compacts were exposed to 40°C/75% RH for up to 6 h. The sample was periodically withdrawn and analyzed for the physical transformations and degradation. Two oxidative degradation products (DPs) were found to be formed, for which dissimilar relations to the degree of disorder and kinetics of formation were observed. The degradation rate of the major DP formation obtained by fitting the exponential model to the experimental data was found to increase up to a certain degree of disorder and decrease with a further increase in the disordered fraction. In contrast, the minor DP formation kinetics was found to increase monotonically with the increase in the disorder content. For the similar crystallinity level, the degradation trend (rate and extent) differed between the single-phase disorder generated by milling and physically mixed two-phase systems. Overall, the study demonstrates the importance of evaluating the physical and chemical (in)stabilities of the disordered solid state of a salt form of a drug substance, generated through mechano-activation.

Synthesis, in silico modelling, and in vitro biological evaluation of substituted pyrazole derivatives as potential anti-skin cancer, anti-tyrosinase, and antioxidant agents

Twenty-five azole compounds (P1-P25) were synthesised using regioselective base-metal catalysed and microwave-assisted approaches, fully characterised by high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), and infrared spectra (IR) analyses, and evaluated for anticancer, anti-tyrosinase, and anti-oxidant activities in silico and in vitro. P25 exhibited potent anticancer activity against cells of four skin cancer (SC) lines, with selectivity for melanoma (A375, SK-Mel-28) or non-melanoma (A431, SCC-12) SC cells over non-cancerous HaCaT-keratinocytes. Clonogenic, scratch-wound, and immunoblotting assay data were consistent with anti-proliferative results, expression profiling therewith implicating intrinsic and extrinsic apoptosis activation. In a mushroom tyrosinase inhibition assay, P14 was most potent among the compounds (half-maximal inhibitory concentration where 50% of cells are dead, IC50 15.9 μM), with activity greater than arbutin and kojic acid. Also, P6 exhibited noteworthy free radical-scavenging activity. Furthermore, in silico docking and absorption, distribution, metabolism, excretion, and toxicity (ADMET) simulations predicted prominent-phenotypic actives to engage diverse cancer/hyperpigmentation-related targets with relatively high affinities. Altogether, promising early-stage hits were identified - some with multiple activities - warranting further hit-to-lead optimisation chemistry with further biological evaluations, towards identifying new skin-cancer and skin-pigmentation renormalising agents.

Carbohydrate Core-Shell Electrosprayed Microcapsules for Enhanced Oxidative Stability of Vitamin A Palmitate

Vitamin A is an essential micronutrient that is readily oxidized. In this study, the encapsulation of vitamin A palmitate (AP) within a core-shell carbohydrate matrix by co-axial electrospray and its oxidative stability was evaluated. The electrosprayed core-shell microcapsules consisted of a shell of octenyl succinic anhydride (OSA) modified corn starch, maltose (Hi-Cap), and a core of ethyl cellulose-AP (average diameter of about 3.7 µm). The effect of different compounds (digestion-resistant maltodextrin, soy protein hydrolysate, casein protein hydrolysate, and lecithin) added to the base core-shell matrix formulation on the oxidative stability of AP was investigated. The oxidative stability of AP was evaluated using isothermal and non-isothermal differential scanning calorimetry (DSC), and Raman and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy methods. The core-shell carbohydrate matrix minimizes the amount of AP present at the microparticle surface, thus protecting AP from oxidation. Furthermore, the most effective oxidation protection was achieved when casein protein hydrolysate was added to the core of the microcapsule due to hydrophobic and hydrogen bond interactions with AP and by the resistant maltodextrin in the shell, which acted as a filler. The utilization of ethanol as a solvent for the dispersion of the core compounds increased the hydrophobicity of the hydrolyzed proteins and contributed to the enhancement of their antioxidant ability. Both the carbohydrate core-shell microcapsule prepared by co-axial electrospray and the addition of oxidation protection compounds enhance the oxidative stability of the encapsulated AP.

Ionic Liquids: New Forms of Active Pharmaceutical Ingredients with Unique, Tunable Properties

This Review aims to summarize advances over the last 15 years in the development of active pharmaceutical ingredient ionic liquids (API-ILs), which make up a prospective game-changing strategy to overcome multiple problems with conventional solid-state drugs, for example, polymorphism. A critical part of the present Review is the collection of API-ILs and deep eutectic solvents (DESs) prepared to date. The Review covers rules for rational design of API-ILs and tools for API-IL formation, syntheses, and characterization. Nomenclature and ionic speciation, and the confusion that these may cause, are highlighted, particularly for speciation in both ILs and DESs of intermediate ionicity. We also highlight in vivo and in vitro pharmaceutical activity studies, with differences in pharmacokinetic/pharmacodynamic depending on ionicity of API-ILs. A brief overview is provided for the ILs used to deliver drugs, and the Review concludes with key prospects and roadblocks in translating API-ILs into pharmaceutical manufacturing.

Drug in Therapeutic Polymer: Sinomenine-Loaded Oxidation-Responsive Polymeric Nanoparticles for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease that frequently involves cartilage damage and the destruction of the bone structure, ultimately resulting in disability and long-term pain. It is clear that overexpression of reactive oxygen species (ROS) and the complex inflammatory microenvironment are the main causes of RA pathogenesis; thereby, the efficacy of any single-drug treatment is limited. Herein, we formulated a therapeutic hyaluronic acid derivative (PAM-HA) with adsorption capacity to the subchondral bone, a long retention time within inflamed joints, and ROS-scavenging capacity, which was used as a drug carrier for realizing the controlled release of sinomenine (Sin) within arthritic joints. This "drug in therapeutic polymer" design strategy was aimed at realizing antioxidant and anti-inflammatory combination therapy for RA. In vivo experiments suggest that PAM-HA@Sin NPs can be retained in the inflamed joints of rats for a long time compared with commercially available free Sin injections. As expected, therapeutic PAM-HA polymeric carriers can increase joint lubrication and reduce oxidative stress, while the released Sin induces downregulation of proinflammatory factors (TNF-α and IL-1β) and upregulation of anti-inflammatory factors (Arg-1 and IL-10) via the NF-κB pathway. In summary, a ROS-scavenging hyaluronic acid (HA) derivative was developed as the nanocarrier for Sin delivery to simultaneously remodel the oxidative/inflammatory microenvironment in RA, which opens up new horizons for the development of therapeutic polymers and the combined therapeutic strategies.

Temperature variations in pharmaceutical storage facilities and knowledge, attitudes, and practices of personnel on proper storage conditions for medicines in southern Malawi

Objective

We assessed the temperature variations in pharmacies and medicine storage areas in southern Malawi and conducted a knowledge, attitude and practices survey for personnel who manage medicine stores in various health facilities.

Methods

This was a longitudinal study design that used installed Tempmate® thermometers in 27 selected health facilities to record temperatures every 15 min for a period of 9 months. In addition, a questionnaire was used to assess the knowledge, attitude, and practices regarding good pharmaceutical storage. Observations were also made on the storage structures of the facilities and compared with the mean kinetic temperature.

Results

Storage temperature ranged from 13.8°C to 42°C with mean kinetic temperature (MKT) being 25.3°C (95% CI 24.4-26.2°C). Mean temperature for public facilities was lower (23.8°C) than the faith-based facilities (25.2°C) and private facilities (26.6°C). In terms of level of health care, lower temperatures were recorded in facilities offering tertiary level of care as compared to secondary and primary care facilities, p < 0.001. For the type of storage facilities, storage-in-a-box unit (SIAB) presented lower temperatures than ordinary storage areas (non-SIAB), p < 0.001. Majority of health workers (69%) had good knowledge on proper storage conditions. Air conditioners and thermometers were available in 88.4 and 76.9% of the facilities, respectively. However, few facilities utilized the air conditioners due to electricity problems. About 46.15% of the participants were able to correctly record temperatures (at least twice a day) for the storage facilities, 23.07% did not properly record while 30.77% of the personnel did not keep temperature records at all. Limited storage space was among the challenges that facilities encounter to maintain proper storage conditions.

Conclusion

Despite having the necessary knowledge on proper storage conditions, the pharmacy personnel failed to adhere to good pharmaceutical storage practices due to resource limitations. There is a need for stakeholder interventions such as increasing budget allocation to address the challenges faced by the health facilities.

Molecular Mechanisms Involved in the Chemical Instability of ONC201 and Methods to Counter Its Degradation in Solution

Glioblastoma is one of the most common and aggressive forms of brain tumor, a rare disease for which there is a great need for innovative therapies. ONC201, a new drug substance, has been used in a compassionate treatment program where the choice of dosage form and regimen have yet to be justified. The prior knowledge needed to anticipate ONC201 stability problems has recently been partially addressed, by (i) showing that ONC201 is sensitive to light and oxidation and (ii) identifying the molecular structures of the main degradation products formed. The aim of the work presented here was to improve our understanding of the degradation pathways of ONC201 using data from ab initio calculations and experimental work to supplement the structural information we already published. The C-H bonds located αto the amine of the tetrahydropyridine group and those located alpha to the imine function of the dihydroimidazole group exhibit the lowest bond dissociation energies (BDEs) within the ONC201 molecule. Moreover, these values drop well below 90 kcal.mol-1 when ONC201 is in an excited state (S1; T1). The structures of the photoproducts we had previously identified are consistent with these data, showing that they would have resulted from radical processes following the abstraction of alpha hydrogens. Concerning ONC201's sensitivity to oxidation, the structures of the oxidation products matched the critical points revealed through mapped electrostatic potential (MEP) and average local ionization energy (ALIE). The data obtained from ab initio calculations and experimental work showed that the reactivity of ONC201 to light and oxidation conditions is highly dependent on pH. While an acidic environment (pH < 6) contributes to making ONC201 quantitatively more stable in solution in the face of oxidation and photo-oxidation, it nevertheless seems that certain chemical groups in the molecule are more exposed to nucleophilic attacks, which explains the variation observed in the profile of degradation products formed in the presence of certain antioxidants tested. This information is crucial to better understand the stability results in the presence of antioxidant agents and to determine the right conditions for them to act.

Applying Material Science Principles to Chemical Stability: Modelling Solid State Autoxidation in Mifepristone Containing Different Degrees of Crystal Disorder

Ball-milling and harsh manufacturing processes often generate crystal disorder which have practical implications on the physical and chemical stabilities of solid drugs during subsequent storage, transport, and handling. The impact of the physical state of solid drugs, containing different degrees/levels of crystal disorder, on their autoxidative stability under storage has not been widely investigated. This study investigates the impact of differing degrees of crystal disorder on the autoxidation of Mifepristone (MFP) to develop a predictive (semi-empirical) stability model. Crystalline MFP was subjected to different durations of ambient ball milling, and the resulting disorder/ amorphous content was quantified using a partial least square (PLS) regression model based on Raman spectroscopy data. Samples of MFP milled to generate varying levels of disorder were subjected to a range of (accelerated) stability conditions, and periodically sampled to examine their recrystallization and degradation extents. Crystallinity was monitored by Raman spectroscopy, and the degradation was evaluated by liquid chromatography. The analyses of milled samples demonstrated a competition between recrystallization and degradation via autoxidation of MFP, to different extents depending on stability conditions/exposure time. The degradation kinetics were analyzed by accounting for the preceding amorphous content, and fitted with a diffusion model. An extended Arrhenius equation was used to predict the degradation of stored samples under long-term (25°C/60% RH) and accelerated (40°C/75% RH, 50°C/75% RH) stability conditions. This study highlights the utility of such a predictive stability model for identifying the autoxidative instability in non-crystalline/partially crystalline MFP, owing to the degradation of the amorphous phases. This study is particularly useful for identifying drug-product instability by leveraging the concept of material sciences.

A versatile method to fingerprint and compare the oxidative behaviour of lipids beyond their oxidative stability

In this work we propose the use of isothermal thermogravimetry to evaluate the oxidative stability of a lipid and to evaluate how the glyceride composition affects the entire oxidative process, to quantify the oxidation undertaken by the lipid, and numerically compare the oxidative behaviour of different lipids. The innovative aspect of the present method lies in the acquisition of a prolonged "oxygen uptake" curve (4000-10,000 min) of a lipid under oxygen and in the development of a semi-empirical fitting equation for the experimental data. This provides the induction period (oxidative stability), and allows to evaluate the rate of oxidation, the rate and the magnitude of oxidative degradation, the overall mass loss and the mass of oxygen taken by the lipid upon time. The proposed approach is used to characterize the oxidation of different edible oils with different degrees of unsaturation (linseed oil, sunflower oil, and olive oil) as well as chemically simpler compounds used in the literature to model the autoxidation of vegetable oils and lipids in general: triglycerides (glyceryl trilinolenate, glyceryl trilinoleate and glyceryl trioleate) and methyl esters (methyl linoleate and methyl linolenate). The approach proves very robust and very sensitive to changes in the sample composition.

Azobisisobutyronitrile loaded on mesoporous silica particles: A new stressor for solid-state oxidative forced degradation studies

A new approach for testing drug sensitivity to autooxidative degradation in the solid state is demonstrated in this work. A novel solid-state form of stressing agent for autooxidation has been proposed, based on azobisisobutyronitrile loaded into mesoporous silica carrier particles. The new solid-state form of the stressing agent was applied in degradation studies of two active pharmaceutical ingredients: bisoprolol and abiraterone acetate. The effectiveness and predictivity of the method were evaluated by comparing impurity profiles with those obtained by traditional stability testing of commercial tablets containing the investigated APIs. The results obtained by the new solid-state stressor were also compared with those obtained by an existing method for testing peroxide oxidative degradation in the solid state using a complex of polyvinylpyrrolidone with hydrogen peroxide. It was found that the new silica particle-based stressor was able to effectively predict which impurities could be formed by autooxidation in tablets and that this new approach is complementary to methods for testing peroxide oxidative degradation known from the literature.

Screening Autoxidation Propensities of Drugs in the Solid-State Using PVP and in the Solution State Using N-Methyl Pyrrolidone

Oxidative degradation of drugs is one of the major routes of drug substance and drug product instability. Among the diverse routes of oxidation, autoxidation is considered to be challenging to predict and control, potentially due to the multi-step mechanism involving free radicals. C–H bond dissociation energy (C–H BDE) is evidenced to be a calculated descriptor shown to predict drug autoxidation. While computational predictions for the autoxidation propensity of drugs are both swift and possible, no literature to date has highlighted the relationship between the computed C–H BDE and the experimentally-derived autoxidation propensities of solid drugs. The objective of this study is to investigate this missing relationship. The present work is an extension to the previously reported novel autoxidation approach that involves subjecting a physical mixture of pre-milled polyvinyl pyrrolidone (PVP) K-60 and a crystalline drug under high temperature and pressurized oxygen setup. The drug degradation was measured using chromatographic methods. An improved trend between the extent of solid autoxidation and C–H BDE could be observed after normalizing the effective surface area of drugs in the crystalline state, pointing to a positive relationship. Additional studies were conducted by dissolving the drug in N-methyl pyrrolidone (NMP) and exposing the solution under a pressurized oxygen setup at diverse elevated temperatures. Chromatographic results of these samples indicated a similarity in the formed degradation products to the solid-state experiments pointing to the utility of NMP, a PVP monomer surrogate, as a stressing agent for faster and relevant autoxidation screening of drugs in formulations.

Isolation and structural characterization of two novel oxidative degradation products of losartan potassium active pharmaceutical ingredient using advanced analytical techniques

RATIONALE

Losartan potassium (losartan) is the most frequently utilized antihypertensive medication in the world. However, partial oxidation of losartan produces toxic by-products that could be harmful to living organisms. Therefore, it is necessary to degrade the losartan and identify the potential toxic oxidative degradation products to minimize their formation during manufacturing, formulation, storage, and packing conditions.

METHODS

Oxidative degradation experiments of losartan were performed according to ICH guidelines. The degradation products were detected using ultra-high-performance liquid chromatography-mass spectrometry analysis, isolated by using preparative HPLC, and identified by using high-resolution mass spectrometry and nuclear magnetic resonance spectroscopic techniques.

RESULTS

The degradation products (DP-1, DP-2, and DP-3) were identified as (((2'-(2H-tetrazol-5-yl)-[1,1'-biphenyl]-4-yl)methyl)amino)-2-oxoethylpentanoate, 5-(4'-((2 butyl-4-chloro-5-(hydroxymethyl)-1H-imidazol-1-yl)methyl)-[1,1'-biphenyl]-2-yl)-1H tetrazol-1-ol, and 5-(4'-((2-butyl-4-chloro-5-(hydroxymethyl)-1H-imidazol-1 yl)methyl)-[1,1'-biphenyl]-2-yl)-2H-tetrazol-2-ol, respectively.

CONCLUSIONS

Forced degradation of losartan potassium API under oxidative condition indicates the formation of two major novel oxidative degradation products (DP-2 and DP-3) and one minor known degradation product (DP-1).Preparative HPLC used for the isolation of the resultant DPs and their structures were successfully established using UHPLC-MS, 1H NMR, 13C NMR, HSQC, HMBC, and HRMS spectroscopic techniques.

Application of Design of Experiments in the Development of Self-Microemulsifying Drug Delivery Systems

Oral delivery has become the route of choice among all other types of drug administrations. However, typical chronic disease drugs are often poorly water-soluble, have low dissolution rates, and undergo first-pass metabolism, ultimately leading to low bioavailability and lack of efficacy. The lipid-based formulation offers tremendous benefits of using versatile excipients and has great compatibility with all types of dosage forms. Self-microemulsifying drug delivery system (SMEDDS) promotes drug self-emulsification in a combination of oil, surfactant, and co-surfactant, thereby facilitating better drug solubility and absorption. The feasible preparation of SMEDDS creates a promising strategy to improve the drawbacks of lipophilic drugs administered orally. Selecting a decent mixing among these components is, therefore, of importance for successful SMEDDS. Quality by Design (QbD) brings a systematic approach to drug development, and it offers promise to significantly improve the manufacturing quality performance of SMEDDS. Furthermore, it could be benefited efficiently by conducting pre-formulation studies integrated with the statistical design of experiment (DoE). In this review, we highlight the recent findings for the development of microemulsions and SMEDDS by using DoE methods to optimize the formulations for drugs in different excipients with controllable ratios. A brief overview of DoE concepts is discussed, along with its technical benefits in improving SMEDDS formulations.

Comprehensive study on degradation profile of firocoxib and structural elucidation of its key degradation products

Firocoxib is widely used in veterinary medicine as a non-steroidal analgesic and anti-inflammatory drug substance. Herein, a comprehensive study on the degradation profile of firocoxib was performed through force degradation studies to understand its degradation profile and characterize its major degradation products (DPs). Firocoxib drug substance was subjected to acidic, alkaline, oxidation (H₂O₂, KMnO₄, and K₂Cr₂O₇), thermal (solid and solution state), and photolytic (solid and solution state) stress degradation, as recommended in the ICH guidelines. Firocoxib and its major DPs were adequately separated by investigational HPLC method, which utilized a HALO C18 (100 × 2.1 mm, 2.0 µm) column. Mobile phase-A for the HPLC method is composed of 0.1% formic acid in water and mobile phase-B acetonitrile. A total of six major DPs were observed for firocoxib drug substance under these stress degradation conditions. Structural elucidation of the DPs performed using liquid chromatography-high resolution mass spectrometry and comparison of their fragmentation profile with that of the parent compound. For further structural confirmation of two major DPs, DP-2 and DP-6 were isolated and purified from the stressed samples using a preparative HPLC and analyzed by comprehensive nuclear magnetic resonance (NMR) spectroscopy studies. Most probable mechanistic pathways for the formation of DPs of firocoxib under various stress degradation conditions were postulated to understand its degradation profile. Based on the results from forced degradation, firocoxib was found to be quite stable under basic and thermal conditions, and somewhat unstable under acidic, oxidative, and photolytic conditions. The results of this study should facilitate quality monitoring and establish a stability profile of firocoxib drug substance and drug products. These results may also assist in the design and development of new formulations made with firocoxib drug substance with desired shelf life.

The Impact of the Water Evaporation Rate and Saccharide Excipients on the Oxidative Degradation of Polysorbates During Oven Drying and Spray Drying

In recent years, many fast drying techniques such as spray-drying are being explored as alternatives to biopharmaceutical freeze-drying. Thus, it is essential to understand how the processability of commonly used excipients will be affected when these new techniques are employed. This study reports a series of observations outlining how the thermally-induced oxidative degradation of polysorbates (PS) evolves in liquid to solid transitions, such as those expected in spray-drying. Firstly, the impact of different evaporation rates on the oxidative degradation of aqueous solutions of two different PS types namely, PS20 and PS80, were screened via evaporative solvent casting. The latter revealed that the evaporation rate could critically impact the rate-limiting steps of PS thermal oxidation. In addition, the potential of saccharides as excipients to mitigate the thermal oxidation of PS80 under slow and fast evaporation conditions was investigated. Five different saccharide excipients were screened, i.e., trehalose dihydrate, maltodextrin, hydroxypropyl-β-cyclodextrin, and Dextran 40. Under slow evaporation conditions, only trehalose dihydrate seemed to be beneficial in avoiding the thermal oxidation of PS80. For fast evaporation conditions, hydroxypropyl-β-cyclodextrin prevented the oxidative degradation of PS80. This implies that distinct strategies to mitigate PS oxidative degradation might be necessary depending on the drying process and rates.

Determination of hydroquinone and benzoquinone in pharmaceutical formulations: critical considerations on quantitative analysis of easily oxidized compounds

Hydroquinone is a skin-lightening agent used as an active ingredient in topical dermatological formulations prescribed for treating cutaneous diseases caused by hyperpigmentation. Despite being widely used, some toxicological aspects have been associated with these products, mainly due to overdosage and long-term use combined with the easy oxidation of hydroquinone. In this work, an investigative study has been done to gather enough data for selecting a quantitative analytical method for quality control purposes that considers the ease of oxidation not only within the product but also during the experimental procedures. After studying the influence of pH, reversibility, sampling, and standard solution preparation on the redox reaction between hydroquinone and benzoquinone by using spectroscopic, electrophoretic, and electroanalytical measurements, a reliable, fast, and selective chronoamperometric method was achieved. The optimized method was used for the analysis of samples, previously diluted in Britton-Robinson (BR) buffer (pH 5.5) and methanol (1 : 9, v/v), by applying a potential fixed at 0.4 V. A glassy-carbon working electrode, lab-made Ag/AgCl_(sat) and platinum wire as a reference electrode and auxiliary electrodes, respectively, and BR buffer (pH 5.5) as supporting electrolyte were the additional experimental conditions used. Analytical performance parameters were verified to confirm the applicability of the new method (LOD 4.22 μmol L^-1 and LOQ 14.1 μmol L^-1; recovery mean value of 100% with 0.22% RSD). A gel topical formulation containing 4% (w/w) hydroquinone was analyzed through the developed method for determination of dosage and oxidation traces, and a content of 3.53 ± 0.095% (w/w) was found with no indications of degradation.

Photoexcited Nitroarenes for the Oxidative Cleavage of Alkenes

The oxidative cleavage of alkenes is an integral process that converts feedstock materials into high-value synthetic intermediates^1,2,3. The most viable method to achieve this in one chemical step is with ozone^4,5,6,7, which however poses technical and safety challenges owing to the explosive nature of ozonolysis products^8,9. Herein, we disclose an alternative approach to achieve oxidative cleavage of alkenes using nitroarenes and purple light irradiation. We demonstrate that photoexcited nitroarenes are effective ozone surrogates that undergo facile radical [3+2] cycloaddition with alkenes. The resulting "N-doped" ozonides are safe to handle and lead to the corresponding carbonyl products under mild hydrolytic conditions. These features have enabled the controlled cleavage of all types of alkenes in the presence of a broad array of commonly used organic functionalities. Furthermore, by harnessing electronic, steric, and mediated polar effects, the structural and functional diversity of nitroarenes has provided a modular platform to obtain site-selectivity in substrates containing more than one alkene.