Sawsan M. Amer

Spectrophotometric study for the reaction between fluvoxamine and 1,2-naphthoquinone-4-sulphonate: Kinetic, mechanism and use for determination of fluvoxamine in its dosage forms

Spectrophotometric study was carried out, for the first time, to investigate the reaction between the antidepressant fluvoxamine (FXM) and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 9), an orange-colored product exhibiting maximum absorption peak (lambda(max)) at 470nm was produced. The kinetics of the reaction was investigated and its activation energy was found to be 2.65kcalmol(-1). Because of this low activation energy, the reaction proceeded easily. The stoichiometry of the reaction was determined and the reaction mechanism was postulated. This color-developing reaction was successfully employed in the development of simple and rapid spectrophotometric method for determination of FXM in its pharmaceutical dosage forms. Under the optimized reaction conditions, Beers law correlating the absorbance (A) with FXM concentration (C) was obeyed in the range of 0.6-8microgml(-1). The regression equation for the calibration data was A=0.0086+0.1348C, with good correlation coefficient (0.9996). The molar absorptivity (epsilon) was 5.9x10(4)lmol(-1)cm(-1). The limits of detection and quantification were 0.2 and 0.6microgml(-1), respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the determination of FXM in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.47+/-0.96%. The results obtained by the proposed method were comparable with those obtained by the official method. The proposed method is superior to all the previously reported spectrophotometric methods for determination of FXM in terms of its simplicity and sensitivity. The method is practical and valuable for its routine application in quality control laboratories for analysis of FXM.

Simple Spectrophotometric Method for Determination of Paroxetine in Tablets Using 1,2-Naphthoquinone-4-Sulphonate as a Chromogenic Reagent

Simple and rapid spectrophotometric method has been developed and validated for the determination of paroxetine (PRX) in tablets. The proposed method was based on nucleophilic substitution reaction of PRX with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium to form an orange-colored product of maximum absorption peak (λ max) at 488 nm. The stoichiometry and kinetics of the reaction were studied, and the reaction mechanism was postulated. Under the optimized reaction conditions, Beers law correlating the absorbance (A) with PRX concentration (C) was obeyed in the range of 1–8 μg mL−1. The regression equation for the calibration data was: A = 0.0031 + 0.1609 C, with good correlation coefficients (0.9992). The molar absorptivity (ε) was 5.9 × 105 L mol−1 1 cm−1. The limits of detection and quantitation were 0.3 and 0.8 μg mL−1, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the determination of PRX in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 97.17 ± 1.06 %. The results obtained by the proposed method were comparable with those obtained by the official method.

New Spectrophotometric and Fluorimetric Methods for Determination of Fluoxetine in Pharmaceutical Formulations

New simple and sensitive spectrophotometric and fluorimetric methods have been developed and validated for the determination of fluoxetine hydrochloride (FLX) in its pharmaceutical formulations. The spectrophotometric method was based on the reaction of FLX with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium (pH 11) to form an orange-colored product that was measured at 490 nm. The fluorimetric method was based on the reaction of FLX with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in an alkaline medium (pH 8) to form a highly fluorescent product that was measured at 545 nm after excitation at 490 nm. The variables affecting the reactions of FLX with both NQS and NBD-Cl were carefully studied and optimized. The kinetics of the reactions were investigated, and the reaction mechanisms were presented. Under the optimum reaction conditions, good linear relationships were found between the readings and the concentrations of FLX in the ranges of 0.3–6 and 0.035–0.5 μg mL−1 for the spectrophotometric and fluorimetric methods, respectively. The limits of detection were 0.1 and 0.01 μg mL−1 for the spectrophotometric and fluorimetric methods, respectively. Both methods were successfully applied to the determination of FLX in its pharmaceutical formulations.

Polarographic behavior and determination of finasteride

The polarographic behavior of finasteride at the dropping mercury electrode (DME) was studied adopting direct current (DC(t)), alternating current (AC(t)) and differential-pulse polarography (DPP) modes. In Britton-Robinson buffer (BRb), finasteride exhibited cathodic waves over the pH range 6-12. At pH 10, a well-defined cathodic wave was obtained. The latter could be characterized as being irreversible, diffusion-controlled and partially affected by adsorption phenomenon. The number of electrons involved in the reduction process was accomplished and a proposal of the electrode reaction was presented. The current-concentration plots were rectilinear over the ranges 8-40 and 2-30 microg ml(-1) using DC(t) and DPP modes, respectively. The minimum delectability was 0.2 microg ml(-1) (5.4 x 10(-7) M), for the latter. The proposed method was successfully applied to the determination of finasteride in its commercial capsules and the results obtained were in good agreement with those given with a reference method.

Identification and characterization of in vitro phase I and reactive metabolites of masitinib using a LC-MS/MS method: bioactivation pathway elucidation

Masitinib is a selective tyrosine kinase inhibitor (TKI). It is currently registered in Europe for the treatment of mast cell tumors in dogs. The current study reports the identification and characterization of fourteen phase I metabolites of masitinib by reversed phase liquid chromatography triple quadrupole mass spectrometry (LC-QqQ-MS). Phase I metabolic reactions were reduction, demethylation, hydroxylation, oxidation and N-oxide formation. Structures of the proposed phase I metabolites showed high lability to form reactive metabolites. So incubation was performed in the presence of 1.0 mM GSH or 1.0 mM KCN to check for reactive metabolites. No GSH adduct was found, while eight cyano adduct structures were determined based on full MS scan and MS2 scan data for each metabolite. Interestingly, a literature review showed no previous studies have been made on the in vitro metabolism of masitinib or detailed structural identification of the formed metabolites.

Determination of fusidic acid and sodium fusidate in pharmaceutical dosage forms by first-derivative ultraviolet spectrophotometry

A simple ultraviolet spectrophotometric method for the determination of fusidic acid and its sodium salt has been developed. The proposed method makes use of the weak shoulder present at about 228 nm using a first-derivative technique. The mean recoveries from authentic samples, in the concentration range 3–40 µg ml–1, are 99.8 ± 0.74 and 100.2 ± 0.52% for fusidic acid and sodium fusidate, respectively. The method has been successfully applied to the analysis of pharmaceutical dosage forms; the results obtained are both accurate and precise.

Validated LC-MS/MS Method for the Quantification of Ponatinib in Plasma: Application to Metabolic Stability.

In the current work, a rapid, specific, sensitive and validated liquid chromatography tandem mass-spectrometric method was developed for the quantification of ponatinib (PNT) in human plasma and rat liver microsomes (RLMs) with its application to metabolic stability. Chromatographic separation of PNT and vandetanib (IS) were accomplished on Agilent eclipse plus C18 analytical column (50 mm × 2.1 mm, 1.8 μm particle size) maintained at 21±2°C. Flow rate was 0.25 mLmin-1 with run time of 4 min. Mobile phase consisted of solvent A (10 mM ammonium formate, pH adjusted to 4.1 with formic acid) and solvent B (acetonitrile). Ions were generated by electrospray (ESI) and multiple reaction monitoring (MRM) was used as basis for quantification. The results revealed a linear calibration curve in the range of 5–400 ngmL-1 (r2 ≥ 0.9998) with lower limit of quantification (LOQ) and lower limit of detection (LOD) of 4.66 and 1.53 ngmL-1 in plasma, 4.19 and 1.38 ngmL-1 in RLMs. The intra- and inter-day precision and accuracy in plasma ranged from1.06 to 2.54% and -1.48 to -0.17, respectively. Whereas in RLMs ranged from 0.97 to 2.31% and -1.65 to -0.3%. The developed procedure was applied for quantification of PNT in human plasma and RLMs for study metabolic stability of PNT. PNT disappeared rapidly in the 1st 10 minutes of RLM incubation and the disappearance plateaued out for the rest of the incubation. In vitro half-life (t1/2) was 6.26 min and intrinsic clearance (CLin) was 15.182± 0.477.

Detection and characterization of ponatinib reactive metabolites by liquid chromatography tandem mass spectrometry and elucidation of bioactivation pathways

Ponatinib (PNT), as a multi-targeted tyrosine kinase inhibitor, is active against T315I and other BCR-ABL mutants. PNT is registered in the U.S. and EU under the trade name of Iclusig®. The current study reports the identification and characterization of in vitro metabolites of PNT, which were produced by its incubation with rat liver microsomes (RLMs). PNT and its metabolites were extracted from the incubation mixture by the protein precipitation procedure and the supernatants were injected into high performance liquid chromatography tandem mass spectrometry (LC-MS/MS) equipment. Reversed phase liquid chromatography resolved seven in vitro PNT metabolites. Each metabolite displayed one or more metabolic reaction pathways including N-demethylation, N-oxide formation, oxidation, reduction and hydroxylation. Structures of the PNT metabolites showed high liability to form reactive metabolites. Since bioactivation is often speculated to be responsible for observed idiosyncratic toxicities including hepatotoxicity, incubation of PNT with RLMs was carried out in the presence of 1.0 mM GSH or 1.0 mM KCN to check its reactive metabolites. No GSH adduct was found while four cyano adduct metabolites were determined and their structures were proposed based on the mass scan and product ion data for each metabolite.

Spectrodensitometric determination of clorazepate dipotassium, primidone and chlorzoxazone each in presence of its degradation product.

The present work describes a quantitative thin layer procedure for estimating primidone, clorazepate dipotassium and chlorzoxazone in bulk powders and in dosage forms, each in the presence of its degradation product. The method consists of dissolving the drug in ethanol (for primidone), or methanol (for clorazepate dipotassium and chlorzoxazone) and then spotting this solution on a thin layer of silica gel G254. Quantitation is achieved by comparing the areas under the peaks obtained from scanning the thin layer chromatographic plates in a spectrodensitometer.

Colorimetric determination of cyclophosphamide and ifosphamide

A simple colorimetric method for the determination of cyclophosphamide and ifosphamide in pure and in dosage forms is suggested. It depends on the reaction of the secondary amino group in both, with nitrous acid, thus forming a nitroso derivative which can be measured at 325 nm for cyclophosphamide and 335 nm for ifosphamide. Beers law is obeyed with concentrations from 20 to 90 micrograms ml-1 for cyclophosphamide and from 5 to 100 micrograms ml-1 for ifosphadmie, with repeatability of 99.83 +/- 0.256% and 99.72 +/- 0.649%, respectively. Application to different pharmaceutical preparations has shown no significant difference when compared with the B.P. 1988 method.