Determination of psychostimulants and their metabolites by electrochemistry linked on-line to flowing atmospheric pressure afterglow mass spectrometry.

The flowing atmospheric pressure afterglow (FAPA) ion source operates in the ambient atmosphere and has been proven to be a promising tool for direct and rapid determination of numerous compounds. Here we linked a FAPA-MS system to an electrochemical flow cell for the identification of drug metabolites generated electrochemically in order to study simulated metabolic pathways. Psychostimulants and their metabolites produced by electrochemistry (EC) were detected on-line by FAPA-MS. The FAPA source has never been used before for an on-line connection with liquid flow, neither for identification of products generated in an electrochemical flow cell. The system was optimized to achieve the highest ionization efficiency by adjusting several parameters, including distances and angles between the ion source and the outlet of the EC system, the high voltage for plasma generation, flow-rates, and EC parameters. Simulated metabolites from tested compounds [methamphetamine (MAF), para-methoxy-N-methylamphetamine (PMMA), dextromethorphan (DXM), and benzydamine (BAM)] were formed in the EC cell at various pH levels. In all cases the main products were oxidized substrates and compounds after N-demethylation. Generation of such products and their thorough on-line identification confirm that the cytochrome P450 - driven metabolism of pharmaceuticals can be efficiently simulated in an electrochemical cell; this approach may serve as a step towards predictive pharmacology using a fast and robust design.

Simultaneous determination of benzydamine hydrochloride and five impurities in an oral collutory as a pharmaceutical formulation by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method for the determination of benzydamine hydrochloride and its impurities 3-dimethylaminopropyl 2-benzylaminobenzoate, 3-dimethylaminopropyl-2-aminobenzoate,1-benzyl-1H-indazol-3-ol, 1-benzyl-2-(3-dimethylaminopropyl)-1,2-dihydro-3H-indazol-3-one, and 1-benzyl-3-(3-(3-dimethylaminopropyl)-3-methylamino)propoxy-(1)H-indazole in a collutory formulation is developed. The separation is carried out on a Gemini C(18) (250 × 4.6 mm, 5 µm) column using acetonitrile-methanol-ammonium carbonate buffer (10 mM; pH 10.5) (37.5:37.5:25, v/v/v) as mobile phase at a flow rate of 1.0 mL/min, column temperature 30°C, and UV detection at 218 nm. Famotidine is used as an internal standard. The total run-time is less than 15 min. The analytical curves present coefficients of correlation greater than 0.99, and detection limits are calculated for all analytes. Excellent accuracy and precision are obtained for benzydamine hydrochloride. Recoveries vary from 98.25 to 102.8%, and intra- and inter-day precisions, calculated as the percent relative standard deviation, are lower than 2.2%. Specificity and robustness for benzydamine hydrochloride are also determined. The method allows the quantitative determination of benzydamine hydrochloride and its impurities, and it is suitable for routine analysis in quality control laboratories.

The development and in vitro evaluation of sustained release tablet formulations of benzydamine hydrochloride and its determination.

A novel oral controlled delivery system for benzydamine hydrochloride (BN) was developed and optimized. Hydrophilic matrix tablets of BN were prepared by using hydroxypropylmethylcellulose (HPMC) and chitosan as polymer substance to achieve required sustained release profile. The matrix tablets were prepared both direct compression and wet granulation method. The influence of matrix forming agents and binary mixtures of them on BN release was investigated. The formulated tablets were characterized by hardness, friability, thickness, weight variation and in vitro drug release. The formulated tablets had acceptable physicochemical characters. The quantity of BN present in the tablets and the release medium were estimated by a simple, sensitive, rapid and validated HPLC method. The dissolution results show that increased amount of polymer resulted in reduced and extended drug release. F7 formulation containing 12.5% HPMC and 12.5 % chitosan with direct compression method is the optimum formulation due to its better targeting profile in terms of release. Higuchi (diffusion) and Hixon-Crowell (erosion) kinetic profiles were achieved and this codependent mechanism of drug release was established. This formulation may provide an alternative for oral controlled delivery of BN and be helpful in the future treatment of primary normoreactive types of inflammation.

Spectrophotometric determination of benzydamine HCl, levamisole HCl and mebeverine HCl through ion-pair complex formation with methyl orange.

A simple, rapid and sensitive spectrophotometric method has been proposed for the assay of benzydamine HCl (BENZ), levamisole HCl (LEV) and mebeverine HCl (MBV) in bulk and pharmaceutical formulations. The method based on the reaction of the selected drugs with methyl orange (MO) in buffered aqueous solution at pH 3.6. The formed yellow ion-pair complexes were extracted with dichloromethane and measured quantitatively with maximum absorption at 422 nm. The analytical parameters and their effects on the reported systems are investigated. The extracts are intensely colored and very stable at room temperature. The calibration graphs were linear over the concentration range of 2-10 microg ml(-1) for BENZ, 6-24 microg ml(-1) for LEV and 4-14 microg ml(-1) for MBV. The stoichiometry of the reaction was found to be 1:1 in all cases and the conditional stability constant (K(f)) of the complexes have been calculated. The proposed method was successfully extended to pharmaceutical preparations-tablets. Excipients used as additive in commercial formulations did not interfere in the analysis. The proposed method can be recommended for quality control and routine analysis where time, cost effectiveness and high specificity of analytical technique are of great importance.

Amperometric biosensor based on monoamine oxidase (MAO) immobilized in sol-gel film for benzydamine determination in pharmaceuticals.

The development and application of a flow-through amperometric biosensor for benzydamine determination in anti-inflammatory drugs is described. The biosensor was obtained by physical entrapment of monoamine oxidase in a sol-gel film applied on platinum or carbon paste conducting support. The sol-gel membranes were prepared using an optimum concentration of 3-aminopropyltriethoxy silane, 2-(3,4-epoxycyclohexyl)ethyl-trimethoxy silane, double distilled water saturated with polyethylene glycol 6000 and HCl. The developed biosensors were incorporated in a single channel flow injection system to enable the determination of benzydamine in the concentration range of 0.05-2.5 mmol l(-1) (with platinum based electrode) or within 0.1-2.5 mmol l(-1) (carbon paste based electrode). The operational stability of the bioanalytical system developed was about 3 months permitting approximately 4700 substrate measurements. The flow injection system developed enables a sampling rate of 20-25 samples h(-1) and relative S.D. of results less than 4%. The analytical usefulness of the proposed procedure was evaluated through analysis of commercial pharmaceutical products containing benzydamine, available on the Portuguese market. The results obtained did not differ significantly from the values resulting from analysis of the same products by the method described in the BP Pharmacopoeia.

Determination of benzydamine and its N-oxide in biological fluids by high-performance liquid chromatography.

A simple, sensitive and selective method for the determination of benzydamine in human plasma and urine, and for benzydamine N-oxide in urine, has been developed using high-performance liquid chromatography in the reversed-phase mode. The limit of reliable determination of benzydamine in plasma was 0.5 ng/ml and that in urine 1 ng/ml; the limit of reliable determination of benzydamine N-oxide in urine was 50 ng/ml. The method has been successfully applied to the analysis of these compounds in biological fluids after administration of intravenous and oral doses of benzydamine to human volunteers.