Determination of linezolid in plasma and bronchoalveolar lavage by high-performance liquid chromatography with ultraviolet detection using a fully automated extraction method

The aim of this study was to develop a specific and sensitive high-performance liquid chromatographic assay for the determination of linezolid in human plasma, and bronchoalveolar lavage. The sample extraction was based on a fully automated solid-phase extraction with an OASIS HLB cartridge. The method used ultraviolet detection set at a wavelength of 254 nm and a separation with a Zorbax Eclipse XDB C8 column. The assay has been found linear over the concentration range 0.02-30 microg/ml and 0.04-30 microg/ml for linezolid, respectively, in plasma and bronchoalveolar lavage. It provided good validation data for accuracy and precision (CV <4.64% and 5.08%, accuracy in the range 96.93-102.67% and 97.33-105.67%, respectively, for intra- and inter-day). The assay will be applied to determine the penetration of linezolid in human bronchoalveolar lavage during pharmacokinetic steady-state.     

Determination of levofloxacin in plasma, bronchoalveolar lavage and bone tissues by high-performance liquid chromatography with ultraviolet detection using a fully automated extraction method

The aim of this study was to develop a specific and sensitive high-performance liquid chromatographic (HPLC) assay for the determination of levofloxacin in human plasma, bronchoalveolar lavage and bone tissues. The sample extraction was based on a fully automated liquid-solid extraction with an OASIS cartridge. The method used ultraviolet detection set at a wavelength of 299 nm and a separation with a Supelcosil ABZ+ column. The assay has been found linear over the concentration range 0.25-25 microg/ml for levofloxacin in plasma, 1-6 microg/ml in bronchoalveolar lavage and 0.5-10 microg/g for bone tissues and it provided good validation data for accuracy and precision. The assay will be applied to determine the penetration of levofloxacin in human bronchoalveolar lavage (BAL) and bone tissues during pharmacokinetic steady state.     

Measurement of piperaquine in plasma by liquid chromatography with ultraviolet absorbance detection

Piperaquine (PQ) is an antimalarial drug enjoying a resurgence of use in combination with an artemisinin derivative because of parasite resistance to standard treatments. Its pharmacokinetic properties have not been characterised. An assay for PQ in plasma was developed using solvent extraction and liquid chromatographic separation on a Waters XTerra RP(18) column, with a mobile phase of 7% acetonitrile in water (containing 0.025% trifluoroacetic acid, 0.1% NaCl and 0.008% triethylamine) and UV detection at 340 nm. The assay was linear up to 1000 microg/l. Intra- and inter-day relative standard deviations were <10% (5-500 microg/l) and <21% (5-500 microg/l), respectively. Inter-day limits of quantitation and detection were 5 microg/l and 3 microg/l, respectively. A preliminary pharmacokinetic study in a patient who received 2.56 g of PQ phosphate orally with dihydroartemisinin as four doses over 32 h found an apparent steady-state volume of distribution of 447 l/kg, an apparent oral clearance 0.93 l/h/kg and a terminal half-life of 17.3 days.     

Analysis of the metabolites of ethyl loflazepate by gas chromatography with electron-capture detection

A gas chromatographic assay with electron-capture detection (GC—EC) is described for the metabolites of ethyl loflazepate (Victan), a new benzodiazepine with a potent anti-anxiety activity, in biological fluids. Since the parent drug undergoes a first-pass effect, pharmacokinetic data may only be obtained by measuring the total levels of two of the major metabolites. Accurate data can not be obtained for the metabolites separately since one of them (M1) is chemically transformed to the other (M2) during plasma sampling, storage and extraction.A sensitive, specific and accurate GC—EC assay is developed using a synthetic analogue of M2 as an internal standard. The limit of detection in plasma is approximately 2 ng/ml and the precision about 3% (within-run and between-run).The method is applied to plasma samples collected after oral administration of 2 mg and 4 mg of the drug in tablet form to human volunteers. The results obtained are correlated with those from an existing gas chromatographic—mass spectrometric assay. A very good correlation between the results (inter-laboratory comparison) is obtained, validating both techniques.     

Sensitive liquid chromatography-tandem mass spectrometry method for the simultaneous determination of paracetamol and guaifenesin in human plasma

A rapid and sensitive method for the simultaneous determination of paracetamol and guaifenesin in human plasma was developed and validated, using high-performance liquid chromatographic separation with tandem mass spectrometric detection. After extracted from plasma samples by diethyl ether-dichloromethane (3:2, v/v), the analytes and internal standard osalmide were chromatographed on a C18 column. Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via atmospheric pressure chemical ionization (APCI). The method was linear in the concentration range of 0.05-20.0 microg/ml for paracetamol and 5.0-2000.0 ng/ml for guaifenesin. The intra- and inter-day precision was within 14% for both paracetamol and guaifenesin. The assay accuracy was within +/-2.4% for the analytes. This is the first assay method described for the simultaneous determination of paracetamol and guaifenesin in plasma using one chromatographic run. The method was successfully employed in a pharmacokinetic study after an oral administration of a multicomponent formulation, containing 650 mg paracetamol, 200 mg guaifenesin, 60 mg pseudoephedrine and 20 mg dextrorphan.     

Stereospecific high-performance liquid chromatographic analysis of ibuprofen in rat serum

A simple, rapid and sensitive high-performance liquid chromatographic method was developed for determination of ibuprofen, (+/-)-(R, S)-2-(4-isobutylphenyl)-propionic acid, enantiomers in rat serum. Serum (0.1 ml) was extracted with 2,2,4-trimethylpentane/isopropanol (95:5, v/v) after addition of the internal standard, (S)-naproxen, and acidification with H(2)SO(4). Enantiomeric resolution of ibuprofen was achieved on ChiralPak AD-RH column with ultraviolet (UV) detection at 220 nm without interference from endogenous co-extracted solutes. The calibration curve demonstrated excellent linearity between 0.1 and 50 microg/ml for each enantiomer. The mean extraction efficiency was >92%. Precision of the assay was within 11% (relative standard deviation (R.S.D.)) and bias of the assay was lower than 15% at the limit of quantitation (0.1 microg/ml). The assay was applied successfully to an oral pharmacokinetic study of ibuprofen in rats.     

Sensitive high-performance liquid chromatographic method with fluorescence detection for measurement of vinorelbine plasma concentrations

A high-performance liquid chromatographic (HPLC) method with fluorescence detection for the determination of vinorelbine in plasma is described. The technique was derived from that published by Debal for an assay of vinorelbine in cell culture medium. The modifications concern the preparation procedure for plasma samples (a two-step liquid-liquid extraction from plasma is desribed), optimization of the mobile phase composition, and use of a single C₁₈ column. These changes resulted in an improved sensitivity and reproducibility of the assay and led to its feasibility for clinical pharmacokinetic studies. The range of the assay is 2 to 1000 ng/ml.     

A rapid and sensitive radioimmunoassay for norethisterone

A direct radioimmunoassay for the measurement of norethisterone (NET) in unextracted serum samples was developed. The combined use of a highly specific unpurified antiserum and heat treatment of diluted serum samples obviated both extraction and chromatographic procedures. The direct NET assay fulfilled all the quality control parameters. When this assay was compared with other methods involving either solvent extraction and/or chromatographic purification procedures, no significant differences were observed. The overall results were interpreted as demonstrating that this simple, rapid and reliable NET assay can be used as a helpful tool in metabolic and pharmacokinetic studies of this contraceptive progestogen.     

Rapid determination of valsartan in human plasma by protein precipitation and high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method for the determination of valsartan in human plasma is reported. The assay is based on protein precipitation with methanol and reversed-phase chromatography with fluorimetric detection. The preparation of a batch of 24 samples takes 20 min. The liquid chromatography was performed on an octadecylsilica column (50 mm x 4 mm, 5 microm particles), the mobile phase consisted of acetonitrile -15 mM dihydrogenpotassium phosphate, pH 2.0 (45:55, v/v). The run time was 2.8 min. The fluorimetric detector was operated at 234/374 nm (excitation/emission wavelength). The limit of quantitation was 98 ng/ml using 0.2 ml of plasma. Within-day and between-day precision expressed by relative standard deviation was less than 5% and inaccuracy did not exceed 8%. The assay was applied to the analysis of samples from a pharmacokinetic study.     

Simple and rapid liquid chromatography method for determination of efavirenz in plasma

A simple and rapid high performance liquid chromatographic method for determination of efavirenz in human plasma was developed. The method involved extraction of sample with ethyl acetate and analysis using a reversed-phase C(18) column (150 mm) with UV detection. The assay was linear from 0.0625 to 10.0 microg/ml. The method was specific for efavirenz estimation and the drug was stable in plasma up to one month at -20 degrees C. The average recovery of efavirenz from plasma was 101%. Due to its simplicity, the assay can be used for pharmacokinetic studies and therapeutic drug monitoring of efavirenz.     

Determination of scopoletin in rat plasma by high performance liquid chromatographic method with UV detection and its application to a pharmacokinetic study

A rapid and simple high-performance liquid chromatographic (HPLC) method has been developed and validated for determination of scopoletin in rat plasma using psoralen as internal standard. Chromatographic separation was achieved on a C(18) column using methanol and distilled water (49:51, v/v) containing 0.05% (v/v) phosphoric acid as mobile phase. The UV detector was set at 345 nm. The calibration curve was linear over the range of 0.165-9.90 microg/ml with a correlation coefficient of 0.9994. The recovery for plasma samples of 0.165, 1.32 and 6.60 microg/ml was 93.2%, 95.9% and 95.5%, respectively. The RSD of intra- and inter-day assay variations was less than 6.7%. This HPLC assay is a precise and reliable method for the analysis of scopoletin in pharmacokinetic studies.     

High-performance liquid chromatography-based determination of total isothiocyanate levels in human plasma: application to studies with 2-phenethyl isothiocyanate

Dietary and pharmacologic isothiocyanates (ITCs) may play a role in reducing the risk of certain cancers. The quantification of ITCs in humans is important both for epidemiological and pharmacokinetic studies. We describe a modification of an HPLC-based assay of urinary ITCs for use with human plasma. The assay utilizes the cyclocondensation reaction of 1,2-benzenedithiol with ITCs present in human plasma, followed by a two-step hexane extraction and analysis by HPLC using UV detection at 365 nm. The method shows linearity and reproducibility with human plasma over a range of 49-3003 nM phenethyl isothiocyanate (PEITC) (r(2) = 0.996 +/- 0.003). A similar degree of linearity was seen with two other biologically occurring conjugates of PEITC: PEITC--N-acetylcysteine (PEITC--NAC) and PEITC--glutathione (PEITC--GSH). The recovery of PEITC assessed on multiple days was 96.6 +/- 1.5% and was 100% for PEITC--GSH and PEITC--NAC. The reproducibility of the assay on multiday samplings showed a mean %CV of 6.5 +/- 0.3% for PEITC, 6.4 +/- 4.3 for PEITC--NAC and 12.3 +/- 3.9 for PEITC--GSH. In clinical studies, mean plasma ITC level of 413 +/- 193 nM PEITC equivalents was determined for a non-dietary-controlled group of 23 subjects. Multiday analysis data from pharmacokinetic plasma sets of 3 subjects taking a single dose of PEITC at 40 mg showed a good CV (range: 16-21%). The applicability of the methodology to pharmacokinetic studies of PEITC in humans is demonstrated.     

Determination of intoplicine, a new antitumour drug, in human whole blood and plasma by normal-phase high-performance liquid chromatography with fluorescence detection

Intoplicine, a benzopyrido-indole derivative, is a novel anticancer agent currently under phase I clinical evaluation. A selective, sensitive normal-phase high-performance liquid chromatographic (HPLC) assay with fluorescence detection, suitable for the determination of intoplicine in human plasma and whole blood, is described. The sample pretreatment involves a protein precipitation step with 2-propanol. The reported assay was validated, and the stability of the analyte in plasma, in whole blood and in the extraction fluid was investigated. The method has been implemented in a pharmacokinetic phase I clinical trial with intoplicine given as a 24-h intravenous infusion.     

Determination of lefucoxib in rat plasma, urine, and feces by high-performance liquid chromatography with fluorescence detection: application in pharmacokinetic studies

A sensitive, specific, and reproducible high-performance liquid chromatography (HPLC) method with fluorescence detection was developed for determination of lefucoxib in rat plasma, urine, and feces. The method involved liquid-liquid extraction using methyl tert-butyl ether, and celecoxib was used as the internal standard. The chromatographic separation was performed on a Kromasil C18 column (250.0 mm x 4.6 mm, 5.0 microm) with a mobile phase gradient consisting of water and methanol at a flow rate of 1 ml min(-1). The assay was linear in the range of 5.0-1000.0 ng ml(-1) with a correlation coefficient (r) of 0.9994. The limit of quantification was 5.0 ng ml(-1). Inter- and intra-assay precisions were 相似文献   

Liquid chromatography-tandem mass spectrometric assay for the PARP-1 inhibitor olaparib in combination with the nitrogen mustard melphalan in human plasma

A bioanalytical assay for the new poly(ADP-ribose) polymerase-1 inhibitor olaparib in combination with melphalan was developed and validated. For the quantitative assay, human plasma samples were pre-treated on ice using protein precipitation with 2% (v/v) acetic acid in acetonitrile containing erlotinib and melphalan-d? as internal standards. The extract was diluted with water and injected into the chromatographic system. This system consisted of a sub-2 μm particle, trifunctional bonded octadecyl silica column with an isocratic elution using 0.01% (v/v) of formic acid in a mixture of water and methanol. The eluate was transferred into the electrospray interface with positive ionization and the analyte was detected in the selected reaction monitoring mode of a triple quadrupole mass spectrometer. The assay was validated in a 10-5000 ng/ml calibration range for both drugs. The lowest level of this range corresponded to the lower limit of quantification. Within day precisions were 3.0-9.3%, between day precisions 6.0-9.8% and accuracies were between 101 and 110% for the whole calibration range. After validation the assay was used to assess the pharmacokinetics of olaparib in a patient with metastatic breast carcinoma. In addition, systemic exposure of melphalan was monitored in patients subjected to isolated hepatic perfusion with this drug. Both applications show that the new assay can be applied for human pharmacokinetic studies for both drugs.     

Simultaneous determination of levomepromazine,midazolam and their major metabolites in human plasma by reversed-phase liquid chromatography

A sensitive and reliable high-performance liquid chromatographic (HPLC) assay is a prerequisite for pharmacokinetic analysis of continuous infusion of levomepromazine adjuvant to midazolam. We developed such a method to determine the levels of levomepromazine, midazolam and their major metabolites (levomepromazinesulfoxide, desmethyl-, didesmethyllevomepromazine, O-desmethyllevomepromazine and alpha-hydroxy-midazolam) simultaneously. Desmethylclomipramine was used as an internal standard (I.S.). The lower limit of quantification of this assay was set for levomepromazine 4.1 microg/l, levomepromazinesulfoxide 4.9 microg/l, O-desmethyllevomepromazine 18.4 microg/l, alpha-hydroxymidazolam 26.6 microg/l, midazolam 23.4 microg/l, didesmethyllevomepromazine 15.8 microg/l, and desmethyllevomepromazine 6.6 microg/l. The between- and within day assay variations were commonly below 5%. The recovery in human plasma for the different analytes varied between 85 and 11%. The accuracy of this assay varied between 95 and 105% for the different concentrations. The linearity of this assay was set between 25 and 800 microg/l (r(2)>0.999 of the regression line). The first results of pharmacokinetic analysis of midazolam indicated that half-life varied between 1.1 and 1.9 h. Pharmacokinetic analysis using a one-compartment model of levomepromazine revealed that the apparent volume of distribution was 4.1+/-2.4 l per kg lean body mass and the metabolic clearance was 309+/-225 l per hour per 70 kg. This assay proved to be robust and reproducible. It can reliably be used for further study of the pharmacokinetics of continuous infusion of levomepromazine.     

Rapid determination of tamsulosin in human plasma by high-performance liquid chromatography using extraction with butyl acetate

A high-performance liquid chromatographic method with fluorescence detection for the determination of tamsulosin in human plasma is reported. The sample preparation involved liquid-liquid extraction of tamsulosin from alkalised plasma with butyl acetate and back-extraction of the drug to the phosphate buffer (pH 2). Butyl acetate is preferable to more commonly used ethyl acetate because of its much lower solubility in water. Liquid chromatography was performed on an octadecylsilica column (55 mm x 4 mm, 3 microm particles), the mobile phase consisted of acetonitrile-30 mM dihydrogenpotassium phosphate (25:75 v/v). The run time was 3.5 min. The fluorimetric detector was operated at 228/326 nm (excitation/emission wavelength). An analogue of tamsulosin, (R)-5-[2-[(3-(2-ethoxyphenoxy)propyl)amino]-2-methylethyl]-2-methoxybenzensulfonamide was used as the internal standard. The limit of quantitation was 0.4 ng/ml using 1 ml of plasma. Within-day and between-day precision expressed by relative standard deviation was less than 10% and inaccuracy did not exceed 5%. The assay was applied to the analysis of samples from several pharmacokinetic studies.     

Stereospecific determination of tiaprofenic acid in plasma: problems with drug degradation

A sensitive stereospecific high-performance liquid chromatographic assay for the quantification of tiaprofenic acid in human plasma was developed. The procedure involved extraction of tiaprofenic acid from acidified plasma into hexane-diethyl ether (8:2, v/v). Stereospecific separation was achieved with a prepacked ga₁-acid glycoprotein column without derivatization. The mobile phase consisted of 2% 2-propanol in 0.01 M phosphate buffer, pH 6.5. Tiaprofenic acid was detected at 317 nm. The limit of quantification was found to be 25 ng/ml for each enantiomer using a 0.5 ml plasma sample. The assay was reproducible and accurate to be applied to the stereoselective pharmacokinetic analysis of tiaprofenic acid in plasma. Because of photoinstability of tiaprofenic acid plasma sampling and sample extraction should be performed under light protection.     

High-performance liquid chromatographic determination of 1-β- -arabinofuranosyl-E-5-(2-bromovinyl)uracil and its metabolite (E)-5-(2-bromovinyl)uracil in serum

A high-performance liquid chromatographic method was developed to assay 1-β- -arabinofuranosyl-E-5-(2-bromovinyl)uracil and its metabolite (E)-5-(2-bromovinyl)uracil in serum. The chloro analogue of the parent drug is used as internal standard. Human serum samples were assayed to establish the pharmacokinetic parameters. Acetonitrile, used as a protein precipitant, was evaporated to dryness and the residue, containing the analytes and internal reference, was dissolved in mobile phase prior to chromatographic analysis. The minimum quantifiable level was 0.02 μg of each analyte per ml of serum.     

Determination of moxifloxacin (BAY 12-8039) in plasma and lung tissue by high-performance liquid chromatography with ultraviolet detection using a fully automated extraction method with a new polymeric cartridge

The aim of this study was to develop a high-performance liquid chromatographic (HPLC) assay for the determination of moxifloxacin in human plasma and lung tissue. The assay was based on HPLC with a Supelcosil ABZ+ column and ultraviolet detection set at a wavelength of 296 nm. The extraction procedure was characterized by a fully automated liquid–solid extraction using an OASIS column for the solid phase. The assay has been found to be linear and validated over the concentration range 3.2 to 0.025 μg/ml for moxifloxacin in plasma and from 16 to 0.25 μg/g for moxifloxacin in lung tissue. In future, the assay will support the pharmacokinetic study of the penetration of moxifloxacin in human lung tissue.