Fesoterodine stress degradation behavior by liquid chromatography coupled to ultraviolet detection and electrospray ionization mass spectrometry

Stability-Indicating RP-HPLC Method for the Estimation of Process-Related Impurities and Degradation Products in Fesoterodine Fumarate by Using a Mass Spectrometric Compatible Mobile Phase

The objective of the present work was to develop a sensitive, selective, accurate and precise stability-indicating HPLC method for quantification of degradation products and process-related impurities in fesoterodine fumarate extended-release tablets. The degradation profile was studied by conducting forced degradation studies and all the degradation products formed during degradation were separated. A chromatographic separation was achieved by using Waters Symmetry C18, 250 × 4.6 mm, 5 μm column, maintained at 30°C. Mobile phase A (0.05% trifluoroacetic acid in water) and mobile phase B (90% of 0.02% TFA in methanol and 10% of water) were used in gradient elution mode. A total of 75 μL of each solution was injected and peak responses were quantified at 220 nm. The method was found specific, precise, accurate, linear, rugged, robust and sensitive. During stability studies of fesoterodine fumarate extended-release tablets, one unknown impurity at relative retention time 1.37 was found increasing beyond the identification threshold. This impurity was isolated by using Preparative HPLC and structure was elucidated using mass and NMR spectroscopy. This method is a simple, inexpensive HPLC method that can be used as a routine quality control test for the estimation of impurities in fesoterodine fumarate extended-release tablets.

Comparison of static and dynamic mode in the electrochemical oxidation of fesoterodine with the use of experimental design approach

Electrochemical conversion of fesoterodine to one of its oxidation products was evaluated with the application of the wall-jet flow cell. A traditional, "static" mode of electrolysis was compared with the "dynamic" mode of cell performance. For statistical assessment of the data, experiments were planned and performed with the application of design of experiments approach, namely Taguchi L18 design. After screening phase, the experimental settings were broadened or adjusted according to the results and optimization was performed. All of the samples were electrolysed with the use of chronoamperometric method in a three electrode system. The electrolysed samples were analysed using UHPLC-PDA-QDA method. The chromatographic run was performed in gradient elution with the application of C8 column. The response was expressed as % area of the main peak found with the PDA detection method whereas QDA detector was used in positive SIM mode for structural confirmation. All data obtained for both screening and optimization were treated together and linear models were adjusted. The use of large-surface glassy carbon electrode along with pH~7 were found to be the most significant factors influencing electrochemical oxidation of fesoterodine in both modes. The major differences were identified in terms of voltage applied to the electrodes which yielded the highest amounts of oxidation product. Evolution of electrochemical methods may serve as complementary technique in stress degradation studies in pharmaceutical industry.

Stability Study of Finasteride: Stability-Indicating LC Method, In Silico and LC-ESI-MS Analysis of Major Degradation Product, and an In Vitro Biological Safety Study

Stability studies of the pharmaceutically important compound finasteride were conducted in order to evaluate decomposition of the drug under forced degradation conditions. A simple stability-indicating liquid chromatography method was developed and validated for the evaluation of finasteride and degradation products formed in pharmaceutical preparations and the raw material. Isocratic LC separation was achieved on a C18 column using a mobile phase of o-phosphoric acid (0.1% v/v), adjusted to pH 2.8 with triethylamine (10% v/v) and acetonitrile (52:48 v/v), with a flow rate of 1.0 mL min-1. The alkaline degradation kinetics of the drug were also evaluated and could be best described as second-order kinetics under the experimental conditions applied for the tablets and raw material. Based on in silico studies and molecular weight confirmation, a comprehensive degradation pathway for the drug and the identity of its major product could be suggested without complicated isolation or purification processes. Furthermore, a biological safety study was performed to evaluate the effect of the degraded sample in relation to the intact molecule. The results showed that the degraded sample affected the cell proliferation. Therefore, these studies show that special care must be taken during the manipulation, manufacture and storage of this pharmaceutical drug.

Monolithic LC method applied to fesoterodine fumarate low dose extended-release tablets: Dissolution and release kinetics

A dissolution test for fesoterodine low dose extended-release tablets using liquid chromatographic (LC) method equipped with a C₁₈ monolithic column was developed and validated. LC system was operated isocratically at controlled temperature (40 °C) using a mobile phase of acetonitrile:methanol:0.03 M ammonium acetate (pH 3.8) (30:15:55, v/v/v), run at a flow rate of 1.5 mL/min and detected at 208 nm. The best dissolution conditions for this formulation were achieved using a USP apparatus 2 (paddle) at 100 rpm and 900 mL of phosphate buffer at pH 6.8 as the dissolution medium. Validation parameters such as the specificity, linearity, accuracy, precision, and robustness were evaluated according to international guidelines, giving results within the acceptable range. The kinetic parameters of drug release were also investigated using model-dependent methods and the dissolution profiles were best described by the Higuchi model. The validated dissolution test can be applied for quality control of this formulation.

A new splitting method for both analytical and preparative LC/MS

This paper presents a novel splitting method for liquid chromatography/mass spectrometry (LC/MS) application, which allows fast MS detection of LC-separated analytes and subsequent online analyte collection. In this approach, a PEEK capillary tube with a micro-orifice drilled on the tube side wall is used to connect with LC column. A small portion of LC eluent emerging from the orifice can be directly ionized by desorption electrospray ionization (DESI) with negligible time delay (6~10 ms) while the remaining analytes exiting the tube outlet can be collected. The DESI-MS analysis of eluted compounds shows narrow peaks and high sensitivity because of the extremely small dead volume of the orifice used for LC eluent splitting (as low as 4 nL) and the freedom to choose favorable DESI spray solvent. In addition, online derivatization using reactive DESI is possible for supercharging proteins and for enhancing their signals without introducing extra dead volume. Unlike UV detector used in traditional preparative LC experiments, this method is applicable to compounds without chromophores (e.g., saccharides) due to the use of MS detector. Furthermore, this splitting method well suits monolithic column-based ultra-fast LC separation at a high elution flow rate of 4 mL/min. Figure ᅟ

Investigation of ex vivo stability of fesoterodine in human plasma and its simultaneous determination together with its active metabolite 5-HMT by LC-ESI-MS/MS: Application to a bioequivalence study

Fesoterodine is a non-selective muscarinic-receptor antagonist, used in the treatment of overactive bladder syndrome. A highly sensitive, selective and rapid method has been developed for the simultaneous determination of fesoterodine and its active metabolite, 5-hydroxymethyl tolterodine (5-HMT) in human plasma by liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS). Due to rapid conversion of parent drug to 5-HMT, ex vivo stability of fesoterodine in human plasma was extensively studied to optimize the extraction protocol. The analytes and their deuterated analogs were quantitatively extracted from 100μL human plasma by liquid-liquid extraction in methyl tert-butyl ether: n-hexane. The chromatographic separation of analytes was achieved on a Kromasil C18 (100mm×4.6mm, 5μm) column under isocratic conditions. The method was validated over a dynamic concentration range of 0.01-10ng/mL for both the analytes. Ion-suppression effects were investigated by post-column infusion of analytes. The precision (% CV) values for the calculated slopes of calibration curves, which would reflect the relative matrix effect, were less than 1.5% for both the analytes. The intra-batch and inter-batch precision (% CV) across quality control levels varied from 1.82 to 3.73% and the mean extraction recovery was >96% for both the analytes. The method was successfully applied to a bioequivalence study of 8mg fesoterodine tablet formulation (test and reference) in 12 healthy Indian subjects under fasted and fed condition. The assay reproducibility estimated by reanalysis of incurred samples showed a change of ±12.0%.

Determination of lumiracoxib by a validated stability-indicating MEKC method and identification of its degradation products by LC-ESI-MS studies

A stability-indicating MEKC method was developed and validated for the analysis of lumiracoxib (LMC) in pharmaceutical formulations using nimesulide as the internal standard (IS). Optimal conditions for the separation of LMC and degradation products were investigated. The method employed 50 mM borate buffer and 50 mM anionic detergent SDS solution at pH 9.0. MEKC method was performed on a fused-silica capillary (50 μm id; effective length, 40 cm) maintained at 30°C. The applied voltage was 20 kV and photodiode array (PDA) detector was set at 208 nm. The method was validated in accordance with the International Conference on Harmonisation requirements. The stability-indicating capability of the method was established by enforced degradation studies combined with peak purity assessment using PDA detection. The degradation products formed under stressed conditions were investigated by LC-ESI-MS and the two degraded products were identified. MEKC method was linear over the concentration range of 5-150 μg/mL (r(2) =0.9999) of LMC. The method was precise, accurate, with LOD and LOQ of 1.34 and 4.48 μg/mL, respectively. The robustness was proved by a fractional factorial design evaluation. The proposed MEKC method was successfully applied for the quantitative analysis of LMC in tablets to support the quality control.