Development and validation of stability indicating HPLC methods for related substances and assay analyses of amoxicillin and potassium clavulanate mixtures

Investigation of aclidinium bromide degradation by stability-indicating HPLC methods, characterization of impurities by NMR, and identification of degradation products by LC-MS

Aclidinium bromide (ACL) is a long-acting muscarinic receptor antagonist used for the long-term treatment of chronic obstructive pulmonary disease (COPD). The aim of this study was to investigate the degradation of aclidinium bromide under stress and stability testing conditions, for which we developed and validated the first stability-indicating, specific, precise, accurate, and robust assay and related substances HPLC methods. Nine of the compounds used as reference standards were synthesized and fully characterized by 1H and 13C NMR, MS, and FTIR techniques. Two of these molecules, namely ACL-dimer and ACL-desphenyl, are novel compounds and reported herein for the first time. Hydrolysis of aclidinium resulted in major degradation via the formation of ACL-desDTG and DTGA metabolites. ACL-desphenyl and phenol were observed only under oxidative conditions at very low levels (< 0.10%), while ACL-hydroxy, known as a metabolite of aclidinium and confirmed by LC/QDa and LC/Q-TOF m/z data, formed under oxidative stress-testing conditions, UV light, and daylight. The identification of two impurities formed only when aclidinium bromide was treated with hydrogen peroxide was done by LC/QDa and LC/Q-TOF studies and the novel structures were proposed as ACL-bromophenoxy and ACL-bromothiophenyl formed via bromination of the phenyl and thiophene ring on the aclidinium, respectively. The stress and photostability testing studies showed that the aclidinium bromide drug substance is not sensitive to elevated temperature (105 °C, 10 days), slightly sensitive to daylight and UV-radiation, and it showed significant degradation under all hydrolysis and oxidizing conditions. The related substances HPLC method reported herein is also capable to monitor the potential genotoxic impurity 3-bromopropoxybenzene (3-BPB), a class 2 impurity according to ICH M7, and ensures that the impurity remains below the threshold of toxicological concern (TTC) limit, making it safe for patients.

Development and validation of stability indicating UPLC methods for related substances and assay analyses of ricobendazole hydrochloride

Ricobendazole hydrochloride is an active ingredient of a veterinary antiparasitic drug. The aim of this study was to investigate the degradation of ricobendazole hydrochloride under stress and stability testing conditions, for which we developed and validated the first stability indicating, specific, precise, accurate, and robust assay and related substances UPLC methods. The Acquity UPLC BEH C18 column was used for the related substances and assay analyses of ricobendazole hydrochloride, and the analyses were performed at 25 °C sample and 30 °C column temperatures with a 2 µL injection volume. In both methods, a mixture of water and methanol (60:40, v/v) was used as the diluent, mobile phase A was a phosphate buffer (50 mM potassium dihydrogen phosphate solution, pH 3.2 ± 0.05, adjusted with 10% o-phosphoric acid), and mobile phase B was a mixture of mobile phase A and acetonitrile (50:50, v/v). For the analysis of related substances, a gradient elution system was used at a flow rate of 0.4 mL/min for 35 min with a detection wavelength of 220 nm, while for the assay analysis; a gradient elution system was used at a flow rate of 0.3 mL/min for 15 min with a detection wavelength of 290 nm. The calibration curves showed excellent linearity with high R-squared (R2) values for each compound, ricobendazole (0.9998, 0.249 - 3.740 µg/mL), ricobendazole amine (0.9998, 0.255 - 3.819 µg/mL), albendazole (0.9998, 0.255 - 7.646 µg/mL), and albendazole sulfone (1.0000, 0.251 - 15.090 µg/mL) indicating a strong correlation between the concentrations of the compounds and their respective peak areas in the UPLC analysis. The method showed excellent accuracy with relative standard deviation values of less than 2.5%. The stress and photostability studies showed that ricobendazole hydrochloride was insensitive to daylight and UV radiation and showed significant degradation at elevated temperature (85 °C, 9 days) and under all hydrolysis and oxidation conditions. The major impurity was ricobendazole amine under thermal and hydrolysis conditions, while albendazole sulfone was the major oxidative impurity.

Advanced Analytical Approach Based on Combination of FT-IR and Chemometrics for Quality Control of Pharmaceutical Preparations

Background: The present work represents a feasibility study for the realization of an analytical method finalized to the detection of expired antibiotic tablets. The work focuses on a specific antibiotic drug and represents the preliminary study upstream of a larger-scale work. Methods: attenuated Total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) spectra coupled with sequential preprocessing through an orthogonalization (SPORT) chemometric approach were used to discriminate between expired and compliant tablets. Conclusions: The highest predictive accuracy (93.3% of correct classification rate in external validation, corresponding to 1 misclassified test sample over 15) was achieved by analyzing intact tablets. This represents an excellent result because it gives indications regarding the possibility of determining, in a completely non-destructive way, the presence of expired drugs.

Direct injection green chromatographic method for simultaneous quantification of amoxicillin and amikacin in maternity hospital wastewater (Sagar, India)

Amoxicillin (AMO) and amikacin (AMK) are broad-spectrum antibiotics that are most preferably given post-delivery (normal and cesarian) in the maternity hospitals located in Sagar city (Madhya Pradesh), India. Both the antibiotics make their way through sewage/drainage systems into the environment in the form of metabolized and unmetabolized compounds. Growing concern about the contamination of wastewater by antibiotics requires fast, sensitive and eco-friendly techniques. Therefore a simple, rapid and environmental friendly chromatographic method has been developed for simultaneous determination of AMO and AMK in maternity hospital wastewater samples. A micellar liquid chromatographic (MLC) method was developed with a C₁₈ column (250 mm × 4.6 mm), sodium dodecyl sulphate (SDS; 0.15 M), 1-butanol (7%) as a modifier, pH 5 and photo diode detector (PDA) at 270 nm and 256 nm for AMO and AMK respectively. The method was fast with analysis time below 9 min. In the present MLC method, linearities (r > 0.998), limits of quantification in the range of 0.02-0.04 μg/mL, repeatabilities, and intermediate precision below 4.9% were adequate for the quantification of AMO and AMK. The proposed method can be utilized to detect and quantify both the antibiotics in various samples by hospitals, pharmaceutical companies, pollution control board, municipal corporations, etc.

Oxidation of Drugs during Drug Product Development: Problems and Solutions

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

Amoxicillin chewable tablets intended for pediatric use: formulation development, stability evaluation and taste assessment

To cover the unpleasant taste of amoxicillin (250 mg), maize starch (baby food) and milk chocolate were co-formulated. The raw materials and the final formulations were characterized by means of Dynamic Light Scattering (DLS), Differential Scanning Calorimetry (DSC) and Fourier-Transform Infrared (FT-IR) spectroscopy. To evaluate the taste masking two different groups of volunteers were used, according to the Ethical Research Committee of the Aristotle University of Thessaloniki. The optimization of excipients' content in the tablet was determined by experimental design methodology (crossed D-optimal). Due to the matrix complexity, amoxicillin was extracted using liquid extraction and analyzed isocratically by HPLC. The developed chromatographic method was validated (%Recovery 98.7-101.3, %RSD = 1.3, LOD and LOQ 0.15 and 0.45 μg mL^-1 respectively) according to the International Conference on Harmonization (ICH) guidelines. The physicochemical properties of the tablets were also examined demonstrating satisfactory quality characteristics (diameter: 15 mm, thickness: 6 mm, hardness <98 Newton, loss of mass <1.0%, disintegration time ∼25min). Additionally, dissolution (%Recovery >90) and in vitro digestion tests (%Recovery >95) were carried out. Stability experiments indicated that amoxicillin is stable in the prepared formulations for at least one year (%Recovery <91).

Synthesis and characterization of oxitropium bromide related substances and novel stability indicating HPLC methods

The European Pharmacopoeia (Ph. Eur.) described two separate HPLC methods for determination of organic impurities in oxitropium bromide, a synthetic anticholinergic agent used by inhalation in the treatment of asthma and other bronchial disorders, and a potentiometric titration assay method which is not a stability indicating method. During synthetic process development and analytical studies of oxitropium; besides known Ph. Eur.-impurities new process related and degradation impurities were determined, identified by LC-MS, synthesized, characterized, and then used in development and validation studies of oxitropium analytical methods. As a result of these studies, a single HPLC related substances method was developed and validated according to international conference on harmonisation (ICH) guidelines for determination of all oxitropium related substances by using an inertsil ODS-4 (250 mm × 4.6 mm, 5 μm) column at 15 °C with 50 μL injection volume at a wavelength of 210 nm with gradient elution of phosphate-buffer/acetonitrile mixture flowing at a rate of 1.2 mL/min during 60 min. Also, a stability indicating HPLC assay method was developed and validated by using an XBridge C₁₈ (150 mm × 4.6 mm, 3.5 μm) column at 25 °C with 10 μL injection volume at a wavelength of 210 nm and with phosphate-buffer/acetonitrile (85/15) mixture flowing at a rate of 1.0 mL/min during 10 min. Stress-testing and stability studies of oxitropium bromide was carried out and samples were analyzed by using newly developed stability-indicating HPLC assay and related substances methods.

Determination of flibanserin in the presence of confirmed degradation products by a third derivative emission spectrofluorometric method: Application to pharmaceutical formulation

Flibanserin is a new drug used for the treatment of hypoactive sexual desire disorder. This work is considered the first study concerning the fluorimetric behaviour of flibanserin and its new florescent degradation products. A fast, cost-effective, stability-indicating spectrofluorometric method was developed and validated for the determination of flibanserin in the presence of oxidative degradation products. Stability studies are performed to predict the behaviour of substances under various harsh conditions. Thus, flibanserin was subjected to degradation using hydrogen peroxide. The stability-indicating method was developed and validated per ICH guidelines; it was linear in the range of 0.1-3 μg/mL. The method was accurate and precise as it showed good recoveries between 98.50 and 100.90% and relative standard deviation less than 2%, respectively, and no significant differences were found after statistical comparison with the in-house HPLC method. In addition, the structures of the oxidative degradation products were confirmed using infrared spectroscopy and mass spectrometry, and the proposed degradation pathway was predicted.

Cold Chain-Free Storable Hydrogel for Infant-Friendly Oral Delivery of Amoxicillin for the Treatment of Pneumococcal Pneumonia

Pneumonia is the major cause of death in children under five, particularly in developing countries. Antibiotics such as amoxicillin greatly help in mitigating this problem. However, there is a lack of an infant/toddler-friendly formulation for countries with limited clean water orr electricity. Here, we report the development of a shear-thinning hydrogel system for the oral delivery of amoxicillin to infant/toddler patients, without the need of clean water and refrigeration. The hydrogel formulation consists of metolose (hydroxypropyl methylcellulose) and amoxicillin. It preserves the structural integrity of antibiotics and their antibacterial activity over 12 weeks at room temperature. Pharmacokinetic profiling of mice reveals that the hydrogel formulation increases the bioavailability of drugs by ∼18% compared to that with aqueous amoxicillin formulation. More importantly, oral gavage of this formulation in a mouse model of secondary pneumococcal pneumonia significantly ameliorates inflammatory infiltration and tissue damage in lungs, with a 10-fold reduction in bacterial counts compared to those in untreated ones. Given the remarkable antibacterial efficacy as well as the use of FDA-regulated ingredients (metolose and amoxicillin), the hydrogel formulation holds great promise for rapid clinical translation.