Determination Of Zolpidem Research Articles

Determination of zolpidem phenyl-4-carboxylic acid and zolpidem 6-carboxylic acid in hair using gas chromatography-electron ionization-tandem mass spectrometry.

A gas chromatography-electron ionization-tandem mass spectrometric (GC-EI-MS/MS) method was developed and validated for determination of the major metabolites of zolpidem, zolpidem phenyl-4-carboxylic acid (ZPCA) and zolpidem 6-carboxylic acid (ZCA) in human hair. The sample preparation procedure involves decontamination, mechanical pulverization, incubation, extraction and purification prior to instrumental analysis. The extracts were derivatized using hexafluoroisopropanol and heptafluorobutyric anhydride and analyzed by GC-EI-MS/MS. The linear ranges were 8-100 pg/mg for ZPCA and 16-200 pg/mg for ZCA, with the correlation coefficients >0.997. The limits of detection were 1.8 pg/mg for ZPCA and 1.7 pg/mg for ZCA. The recoveries ranged from 77.6 to 111.7%. The intra- and inter-day precisions were within 16.9 and 11.7%, while intra- and inter-day accuracies were -7.0-8.7 and -2.8-7.8%, respectively. The developed method was applied for the analysis of forensic hair samples obtained from suspected zolpidem abusers and the following concentration ranges were monitored: ZPCA 11.9-35.9 pg/mg and ZCA 16.6-21.8 pg/mg. The method proved to be suitable for picogram-level determination of ZPCA and ZCA in human hair.

Quantitation of zolpidem in biological fluids by electro-driven microextraction combined with HPLC-UV analysis.

In this study, for the first time, an electro-driven microextraction method named electromembrane extraction combined with a simple high performance liquid chromatography and ultraviolet detection was developed and validated for the quantitation of zolpidem in biological samples. Parameters influencing electromembrane extraction were evaluated and optimized. The membrane consisted of 2-ethylhexanol immobilized in the pores of a hollow fiber. As a driving force, a 150 V electric field was applied to facilitate the analyte migration from the sample matrix to an acceptor solution through a supported liquid membrane. The pHs of donor and acceptor solutions were optimized to 6.0 and 2.0, respectively. The enrichment factor was obtained >75 within 15 minutes. The effect of carbon nanotubes (as solid nano-sorbents) on the membrane performance and EME efficiency was evaluated. The method was linear over the range of 10-1000 ng/mL for zolpidem (R2 >0.9991) with repeatability ( %RSD) between 0.3 % and 7.3 % (n = 3). The limits of detection and quantitation were 3 and 10 ng/mL, respectively. The sensitivity of HPLC-UV for the determination of zolpidem was enhanced by electromembrane extraction. Finally, the method was employed for the quantitation of zolpidem in biological samples with relative recoveries in the range of 60-79 %.

Validation of a Gas Chromatography/Mass Spectrometry Method for Quantitative Determination of Zolpidem in Whole Blood

Zolpidem was determined quantitatively in blood using a GC/MS method with an internal standard of imipramine hydrochloride. The multiple regression coefficient for the obtained calibration curve was r = 0.999. Metrological assessment of the method used eight statistical parameters. The extraction efficiencies of zolpidem at three concentrations were determined in model blood. Yields of 96 – 99% of the test compound were observed. The method was validated for specificity, detection limit (DL), limit of quantitation (LOQ), linearity, analytical range, accuracy, and precision (repeatability and intralaboratory precision). Statistically processed results were within acceptance limits. The DL for zolpidem in blood was 24 ng/mL; LOQ, 72.7 ng/mL

Валидация методики количественного определения золпидема в цельной крови методом газовой хроматомасс-спектрометрии

Проведено количественное определение золпидема в крови методом ГХ/МС, в качестве внутреннего стандарта использовался имипрамина гидрохлорид. Коэффициент множественной регрессии r для полученной калибровочной прямой составил 0,999. Приведена метрологическая оценка методики по восьми статистическим параметрам. Определена эффективность экстракции золпидема из модельной крови на трех уровнях концентраций, при этом выход исследуемого вещества наблюдался в пределах 96 – 99 %. Проведена валидационная оценка методики по показателям: специфичность, предел обнаружения, предел количественного определения, линейность, аналитическая область методики, правильность, прецизионность (повторяемость и внутрилабораторная прецизионность). При статистической обработке полученные результаты находятся в пределах приемлемости. Предел обнаружения золпидема в крови составил 24 нг/мл; предел количественного определения — 72,7 нг/мл.

Development and validation of a stability-indicating reversed phase HPLC method for the quality control of Zolpidem in bulk and tablet dosage forms

An isocratic stability-indicating reversed phase liquid chromatography (RP-HPLC) method for quantitative determination of Zolpidem in the presence of its stressed degradation products in bulk and commercial tablets was developed and validated. Forced degradation studies were carried out on bulk samples and tablet dosage forms of Zolpidem using acid, base, H2O2, heat, and UV light as described by International Conference on Harmonization (ICH) for stress conditions to demonstrate the stability indicating power of the method. A Perfectsil® Target ODS column (3–5 μm, 125 × 4 mm) was used for chromatographic separation. The mobile phase consisted of methanol-50 mM ammonium acetate buffer (pH 3.7, 40: 60, v/v). The flow rate was 0.7 mL/min and UV detection was optimized at 254 nm. The present method linearity for Zolpidem was investigated in the range of 1–20 μg/mL (r = 0.9998). The limits of detection (LOD) and quantification (LOQ) were 400 and 1000 ng/mL respectively. The method selectivity was evaluated by peak purity test using a diode array detector. There was no interference with detection of Zolpidem and its stressed degradation products.

Determination of zolpidem in human plasma by liquid chromatography-tandem mass spectrometry for clinical application.

Zolpidem (ZPD) is widely described for the short-term treatment of insomnia. We have developed and validated a simple and rapid liquid chromatography analytical method using tandem mass spectrometry (LC-MS/MS) for the quantification of ZPD in human plasma. Using dibucaine as an internal standard (IS), the analyte was extracted with methyl t-butyl ether (MTBE). Chromatographic separation of ZPD was performed on a reversed-phase Luna C18 column (50 mm × 2.0 mm i.d., 5 μm particles) with a mobile phase of 10mM ammonium formate buffer (pH 3.0)-methanol (15:85, v/v) at a flow rate of 250 μm/min. The total run-time was 2.5 min and the retention times of ZPD and IS were 0.66 and 0.74 min, respectively. The mass-to-charge transition monitored for quantification of ZPD and IS was 308.2→235.2 and 344.0→271.0, respectively. The lower limit of quantification (LLOQ) using 100 μL of human plasma was 0.05 ng/mL and the calibration curves were linear over a range of 0.05-200 ng/mL (r(2)>0.9964). The mean accuracy and precision for intra- and inter-run validation of ZPD were within acceptable limits. In the present LC-MS/MS method, we showed improved sensitivity for quantification of the ZPD in human plasma using lower volume of plasma compared with previously described analytical methods for ZPD. This validated method was successfully applied to a pharmacokinetic study in humans.

Determination of zolpidem and its metabolites by chromatography-mass spectrometry

Conditions of the simultaneous isolation of various types of zolpidem metabolites from samples of real urine by solid-phase extraction have been optimized. Various derivatives of zolpidem hydroxy- and carboxy-metabolites were obtained; their mass-spectral and gas-chromatographic characteristics have been studied. The results ensure the reliable identification of zolpidem metabolites by gas chromatography-mass spectrometry for chemical toxicological and forensic investigations.

Determination of zolpidem in human hair by micropulverized extraction based on the evaluation of relative extraction efficiency of seven psychoactive drugs from an incurred human hair specimen

A micropulverization method for rapid extraction of psychoactive drugs from hair was developed. A hair sample (10mg) was micropulverized for 10min at 42Hz with 0.2mL of 45% (w/v) aqueous ammonium phosphate (pH 8.4). Liquid–liquid extraction was carried out in the same tube using acetonitrile, and the organic layer was removed and filtered. Conventional methods, including solid–liquid extraction with an ammonium phosphate solution or methanol, were also employed, and the relative extraction efficiencies of amitriptyline, nortriptyline, norfludiazepam, flunitrazepam, 7-aminoflunitrazepam, mianserin and zolpidem with these methods from an incurred human hair specimen were compared using liquid chromatography/tandem mass spectrometry. The highest extraction efficiencies for all the analytes were achieved using the method developed here, even though the extraction time (10min) was short. Overnight methanol extraction has frequently been used for hair analysis; however, the extraction efficiency was not sufficient for amines. The method was successfully applied to the quantification of zolpidem in human hair. The range of quantification was 1–25,000pg/mg, and interday accuracy and precision (n=5) at three concentrations were 1.8–8.8% and 3.3–8.1%, respectively. The developed method was applied to three actual (incurred) samples, for which the concentrations of zolpidem were determined to be 78.9–18,300 (pg/mg).

Bioequivalence Evaluation of Two Brands of Zolpidem Tartrate 10 mg Tablets(Zanilo and Stilnox) in Healthy Male Volunteers

The purpose of the present study was to evaluate the bioequivalence of two zolpidem tartrate tablets, Stilnox tablet(Sanofi-aventis Korea, reference product) and Zanilo tablet(ChoDang Pharm Co., Ltd., Korea, test product), according to the guidelines of Korea Food and Drug Administration(KFDA). After adding an internal standard(cimetropium), 250 plasma samples were extracted using 1.3 mL of ethyl acetate. Extracted compounds were analyzed by HPLC with triple-quadrupole mass spectrometry. This method for determination of zolpidem is proved accurate and reproducible with the limit of quantitation of 1 ng/mL in human plasma. Twenty-four healthy male Korean volunteers received each medicine at the zolpidem tartrate dose of 10 mg in a crossover study. There was one-week washout period between the doses. Plasma concentrations of zolpidem were monitored for over a period of 8 hr after the administration. (the area under the plasma concentration-time curve) was calculated by the linear trapezoidal rule. (maximum plasma drug concentration) and (time to reach ) were compiled from the plasma concentration-time data. Analysis of variance was carried out using logarithmically transformed and . No significant sequence effect was found for all of the bio-availability parameters indicating that the crossover design was properly performed. The 90% confidence intervals for the log transformed data were acceptable range of log 0.8 to log 1.25(e.g., log 0.92-log 1.06 for , log 0.96-log 1.13 for ). The major parameters, and met the criteria of KFDA for bioequivalence indicating that Zanilo tablet is bioequivalent to Stilnox tablet.

Determination of zolpidem in serum microsamples by high-performance liquid chromatography and its application to pharmacokinetics in rats

A single-solvent extraction step high-performance liquid chromatographic method is described for quantitating zolpidem in rat serum microsamples (50 μl). The separation used a 2.1 mm I.D. reversed-phase OD-5-100 C 18 column, 5 μm particle size with an isocratic mobile phase consisting of methanol–acetonitrile–26 m M sodium acetate buffer (adjusted to pH 2.0 with 40% phosphoric acid) containing 0.26 m M tetrabutylammonium phosphate (13:10:77, v/v/v). The detection limit was 3 ng/ml for zolpidem using an ultraviolet detector operated at 240 nm. The recovery was greater than 87% with analysis performed in 12 min. The method is simple, rapid, and applicable to pharmacokinetic studies of zolpidem after administering two intravenous bolus doses (1 and 4 mg/kg) in rats.

Rapid and simple method for the determination of zolpidem in human plasma by high-performance liquid chromatography.

A simple and reproducible method for the determination of zolpidem in human plasma is presented. This method involves protein precipitation with methanol (2 ml of methanol are added to 0.5 ml of plasma) and reversed-phase chromatography with fluorescence detection (excitation wavelength 244 nm, emission wavelength 388 nm). The mobile phase consists of methanol-30 mM dihydrogen potassium phosphate-triethylamine (30:69:1). pH of the aqueous part of the mobile phase is 6.8. No internal standard is required. Limit of quantitation is 1.5 ng/ml and the calibration curve is linear up to 400 ng/ml. Within-day and between-day precision expressed by relative standard deviation is less than 5% and inaccuracy also does not exceed 9%. The assay is useful for pharmacokinetic studies.

Determination of Zolpidem and Zopiclone in Serum by Capillary Column Gas Chromatography

□ A gas chromatographic method using a short, high- resolution capillary column connected to a specific thermoionic detector and requiring a simple and short extraction step without evaporation was developed for the rapid and precise determination of two new hypnotics, Zolpidem and zopiclone, in serum at concentrations >5 ng/mL. The assay was linear between 5 and 200 ng/ml, with coefficients of intra- and interassay variation <5% for both. The method was validated and then used to analyze Zolpidem serum concentrations in nine rabbits after oral administration of 0.5 mg/kg and zopiclone serum concentrations in six patients treated orally with a 7.5-g dose.