Green conventional and first-order derivative fluorimetry methods for determination of trimebutine and its degradation product (eudesmic acid). Emphasis on the solvent and pH effects on their emission spectral properties.

In this report, the fluorescence properties of the antimuscarinic drug trimebutine maleate (TRB) were fully studied and characterized. TRB exhibited intrinsic fluorescence that is greatly dependent on the local environmental factors including the solvent nature and the pH. Yet, its fluorescence was not significantly influenced by the existence of some surface active agents and polymer. The outcomes of this investigation verified that TRB fluorescence emission is intense in ethanol: 1.0 M aqueous acetic acid (9:1, v/v) with emission maxima at 357 nm and excitation maxima at 270 nm. Whereas, going towards higher pH causes fluorescence quenching. These conditions permitted ultrasensitive fluorimetric determination of TRB over the concentration range of 2.00-1500.0 ng/mL with a lower detection limit of 0.40ng/mL Application for the determination of TRB in tablets, ampoule and suspension was successfully achieved with %recoveries ranged between 98.21-100.17%. Furthermore, a first order derivative fluorimetric method was validated for resolving and simultaneous determination of TRB and its degradation product and impurity, eudesmic acid (EUA) making use of the pH-mediated fluorescence spectral shift of EUA. An ethanolic solution containing acetate buffer (pH 5.3) was used for this goal with excitation at 255 nm and measurement of the first order derivative peak amplitudes at respective zero-crossing points of 375 and 351 nm over the corresponding concentration ranges of 20.00-500.00 and 10.00-300.00 ng/mL for TRB and EUA, respectively. The two methods were assessed regarding greenness and eco-friendship by the National Environmental Methods Index and analytical eco-scale score approaches which confirmed their excellent greenness and safety.

Discovery of a novel trimebutine metabolite and its impact on N-desmethyltrimebutine quantification by LC-MS/MS.

BACKGROUND: A failure in incurred sample reanalysis (ISR) for N-desmethyltrimebutine (NDMT), during the analysis of a trimebutine-containing drug GIC-1001 Phase I study, led to the discovery of a never-before reported metabolite of trimebutine. RESULTS: A positive bias for NDMT during the ISR and post-reconstitution stability evaluations indicated the presence of an unstable metabolite of NDMT. Precursor ion scans performed on freshly extracted samples enabled the identification of this metabolite to be the NDMT glucuronide conjugate and its fragmentation pattern suggested that the glucuronide moiety was attached at the N-terminal of NDMT. CONCLUSIONS: An acidification step was introduced in the extraction procedure to completely hydrolyze the glucuronide and measure the total NDMT in plasma, rendering this method a successful fit-for-purpose assay.

Analytical studies on the charge transfer complexes of loperamide hydrochloride and trimebutine drugs. Spectroscopic and thermal characterization of CT complexes.

Charge transfer complexes of loperamide hydrochloride (LOP.HCl) and trimebutine (TB) drugs as electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π-acceptors in acetonitrile were investigated spectrophotometrically to determine the cited drugs in pure and dosage forms. The reaction gives highly coloured complex species which are measured spectrophotometrically at 460, 415 and 842nm in case of LOP.HCl and at 455, 414 and 842nm in case of TB using DDQ, TCNE and TCNQ reagents, respectively. The optimum experimental conditions have been studied carefully and optimized. Beer's law was obeyed over the concentration ranges of 47.70-381.6, 21.50-150.5 and 10.00-100.0µgmL(-1) for LOP.HCl and 37.85-264.9, 38.75-310.0 and 7.75-155.0µgmL(-1) for TB using DDQ, TCNE and TCNQ reagents, respectively. Sandell sensitivity, standard deviation, relative standard deviation, limit of detection and quantification were calculated. The obtained data refer to high accuracy and precision of the proposed method. These results are also confirmed by inter and intra-day precision with percent recovery of 99.18-101.1% and 99.32-101.4% in case of LOP.HCl and 98.00-102.0% and 97.50-101.4% in case of TB using DDQ, TCNE and TCNQ reagents for intra- and inter-day, respectively. These data were compared with those obtained using official methods for the determination of the cited drugs. The stability constants of the CT complexes were determined. The final products of the reaction were isolated and characterized using FT-IR, (1)H NMR, elemental analysis and thermogravimetric analysis (TG). The stoichiometry and apparent formation constant of the complexes formed were determined by applying the conventional spectrophotometric molar ratio method.

End point determination of blending process for trimebutine tablets using principle component analysis (PCA) and partial least squares (PLS) regression.

This study showed near Infrared (NIR) and Raman spectroscopy with a multivariate calibration approach were very effective to determine blend uniformity end-point. A set of 36 trimebutine samples containing magnesium stearate, stearic acid, colloidal silicon oxide, talc as excipients (0.9%∼1.8%) was acquired from six positions during blending processing with U-type blender from 0 to 30 min. Principle component analysis (PCA) with NIR and Raman spectral data was used to confirm the end-point of blending. After 30 min, the scores of principle component (PC) 1 and principle component (PC) 2 for samples moved into one point, which clearly indicated the mixture of sample became homogenous. In addition, NIR and Raman spectroscopy has been applied to the quantitative analysis of 20 trimebutine samples containing 2∼40% in mixture granules, which divided into a calibration set of 15 samples and a prediction set of 5 samples for NIR spectral data. The standard error of calibration (SEC) and standard error of prediction (SEP) are 0.15% and 0.13%, respectively using NIR while SEC and SEP of 0.95% and 0.91% are obtained using Raman spectroscopy. The results showed the NIR and Raman spectroscopy with a multivariate calibration such as PCA and PLS provide the possibility of real time monitoring of homogeneity and content uniformity during blending process.

Determination of trimebutine in pharmaceuticals by differential pulse voltammetry at a glassy carbon electrode.

The differential pulse voltammetric (DPV) determination of trimebutine (TMB) was achieved at a glassy carbon electrode in acetonitrile/0.1 M LiClO4. Trimebutine gave two irreversible, diffusion controlled peaks at 740 and 1318 mV versus Ag/AgCl reference electrode, respectively. The second oxidation peak was used to determine trimebutine concentrations in the range 1-50 microg ml(-1) with a detection limit (3sigmam) of 0.3 microg ml(-1). Precision of the method (RSD, n=6) within- and between-days obtained from six determinations at 5 microg ml(-1) was found to be 0.7 and 1.1%, respectively. The method was successfully applied to the quantitation of TMB in granule dosage form (Debridat) and recoveries between 98.4 and 101% were obtained. Excipients did not interfere with the assay and the results agreed well with those determined by previously established HPLC method.

Spectrophotometric and liquid chromatographic determination of trimebutine maleate in the presence of its degradation products.

Three methods are presented for the determination of trimebutine maleate (TM) in the presence of its degradation products. The first method was based on a high performance liquid chromatographic (HPLC) separation of TM from its degradation products using an ODS column at ambient temperature with a mobile phase consisting of acetonitrile-5 mM heptane sulfonic acid disodium salt (45:55, v/v, pH 4) with UV detection at 215 nm. The second method depends on using first derivative spectrophotometry (1D) by measurement of the amplitude at 252.2 nm. The third method depends on using first derivative of the ratio spectrophotometry (1DD) by measurement of the amplitude at 282.4 nm where a normalized spectrum of 3,4,5-trimethoxy benzoic acid is used as divisor. The proposed HPLC and 1D methods were used to investigate the kinetics of acidic and alkaline degradation processes. The pH-rate profile of degradation of TM in Britton-Robinson buffer solutions within the pH range 2-11.9 was studied.