西格列他钠的体外代谢

目的研究拟治疗2型糖尿病的创新化合物西格列他钠(chiglitazar)的体外代谢速率、代谢酶和代谢转化,为临床应用提供参考。方法采用高效液相-紫外检测(HPLC-UV)的方法测定肝微粒体孵育液中西格列他钠的浓度,用特异性抑制剂的方法分析化合物的代谢酶,用大鼠肝微粒体体外研究西格列他钠可能的代谢产物和代谢途径。结果建立了可靠的测定大鼠肝微粒体中西格列他钠的HPLC分析方法;体外半衰期方法求得西格列他钠的t1/2为27.2min,固有清除率(Clint)为50.9mL.min-1.g-1蛋白;代谢酶研究表明,西格列他钠主要被P450酶中的CYP3A亚型代谢;西格列他钠在大鼠肝微粒体中的代谢主要为羟基化和O-脱烷基化,采用LC/MSn分析共发现了8个代谢物。结论西格列他钠是代谢活跃的化合物,有必要研究代谢产物的活性及临床注意药物相互作用。     

Simple, sensitive and rapid LC-MS/MS method for the quantitation of cerivastatin in human plasma--application to pharmacokinetic studies

A simple and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for estimation of cerivastatin (I) in human plasma, a potent hydroxy-methylglutaryl-coenzyme A reductase inhibitor. The analyte and internal standard (atorvastatin, II) were extracted by liquid/liquid extraction with diethyl ether/dichloromethane (70/30, v/v). The chromatographic separation was performed on reverse phase Xterra ODS column with a mobile phase of water/acetonitrile (30/70, v/v) with 0.03% formic acid. The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 460.4 --> 356.3 and 559.2 --> 440.3 were used to measure I and II, respectively. The lower limit of quantitation was 10pg/mL with a relative standard deviation of less than 15%. Acceptable precision and accuracy were obtained for concentrations over the calibration curve ranges (0.01-10ng/mL). Sample analysis time of 2min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The assay can be used to analyze human plasma samples to support phase I and II clinical studies.     

Determination of capsaicin,nonivamide, and dihydrocapsaicin in blood and tissue by liquid chromatography-tandem mass spectrometry

A sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS-MS) method for the analysis of capsaicin, nonivamide, and dihydrocapsaicin in blood and tissue has been developed. The method utilized a one-step liquid-liquid extraction that yielded an approximate 90% recovery of capsaicinoids from blood. Chomatographic separation of the capsaicinoids was achieved using a reversed-phase high-performance liquid chromatography column and a stepwise gradient of methanol and distilled water containing 0.1% (v/v) formic acid. Identification and quantitation of the capsaicinoids was achieved using electrospray ionization-tandem mass spectrometry monitoring the precursor-to-product-ion transitions for the internal standard octanoyl vanillamide (m/z 280 --> 137), capsaicin (m/z 306 --> 137), dihydrocapsaicin (m/z 308 -->137), and nonivamide (m/z 294 --> 137). Calibration curves, 1.0 to 250 ng/mL, were constructed by plotting concentration versus peak-area ratio (analyte/internal standard) and fitting the data with a weighted quadratic equation. The accuracy of the assay ranged from 90% to 107% for all analytes. The intra-assay precision (%RSD) for capsaicin was 4% at 2.5 ng/mL, 3% at 10 ng/mL, and 7% at 100 ng/mL. The interassay precision (% RSD) for capsaicin was 6% at 2.5 ng/mL, 6% at 10 ng/mL, and 7% at 100 ng/mL. Similar values for inter- and intra-assay precision were obtained for nonivamide and dihydrocapsaicin. This method was used to assay for capsaicinoids in blood and tissue samples collected from rats exposed to capsaicinoids via nose-only inhalation. The concentration of capsaicin in these samples ranged from < 1.0 to 90.4 ng/mL in the blood, < 5.0 to 167 pg/mg in the lung, and < 2.0 to 3.4 pg/mg in the liver.     

LC-ESI-MS测定新的抗胆碱能化合物苯环喹溴铵在大鼠胆汁、尿液和粪便中的含量

目的：首次建立了LC-ESI-MS法测定大鼠胆汁、尿液和粪便中苯环喹溴铵的浓度,对该药在大鼠体内的排泄规律进行研究,为该药在大鼠体内的代谢转化途径的研究和临床试验提供依据。方法：生物样品经过C18固相小柱提取后,采用LC-ESI-MS法进行测定。以1-乙基-苯环喹溴铵为内标,在Hanbon Lichrospher5-C18色谱柱上,甲醇-（含40mmol/L醋酸铵和1%甲酸）水溶液（70：30,v/v）为流动相,流速为0.8mL/min分析胆汁样品;甲醇-（含40mmol/L醋酸铵和1%甲酸）水溶液（75：25,v/v）为流动相,流速为1.0mL/min分析尿液、粪便样品;以气动辅助电喷雾离子化（ESI）为接口技术,选择性正离子监测方式,苯环喹溴铵的分子离子（[M]^＋m/z330.2）和内标1-乙基-苯环喹溴铵的分子离子（[M]＋m/z344.2）作为测定离子。结果：胆汁、尿样、粪便中苯环喹溴铵的回收率均大于77%,日间和日内的变异系数均小于15%。胆汁中苯环喹溴铵在30.15～1507.50ng/mL浓度范围内线性关系良好（r=0.9995）,最低定量限为30.15ng/mL。尿液中苯环喹溴铵在3.02～1507.50ng/mL浓度范围内线性关系良好（r=0.9997）,最低定量限为3.02ng/mL。粪便中苯环喹溴铵在3.02～1507.50ng/mL浓度范围内线性关系良好（r=0.9995）,最低定量限为3.02ng/mL。结论：该方法专属性强,准确可靠,灵敏度高,可满足大鼠鼻腔给药排泄研究中药物浓度测定的要求。     

Analytical issues in HPLC/MS/MS simultaneous assay of furosemide,spironolactone and canrenone in human plasma samples

A new sensitive HPLC/MS/MS method for simultaneous determination of furosemide, spironolactone and canrenone in human plasma samples is presented. Electrospray ionization source (ESI) has been used. The tandem MS detection was performed under MRM conditions, in the negative ion mode for furosemide and indapamide (internal standard 1) and in the positive ion mode for spironolactone, canrenone and nitrazepam (internal standard 2). A simple plasma protein precipitation with acetonitrile was used as sample preparation technique. The chromatographic separation was carried out under the reversed phase mechanism, on a 250 mm length column packed with octadecyl modified silicagel and thermostated at 35 °C. The column was operated under isocratic conditions (3:7 aqueous 0.1% formic acid and methanol, v/v) at a flow rate of 0.8 mL/min. Quantitation intervals of 20–1600 ng/mL for furosemide and 2–100 ng/mL for spironolactone and canrenone have been concluded through validation. Precision and accuracy were situated within the accepted thresholds (maximum 15% relative standard deviation and ±15% percentage bias). The most sensitive aspects relating to the analytical method development and validation were highlighted and critically assessed in order to reach an objective opinion about the real performances and inherent applicability of the method in bioanalysis.     

Measurement of haloperidol in human breast milk by high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for the assay of haloperidol in human breast milk. The method involves rapid extraction of haloperidol and chromatography with a reversed-phase C18 column and a mobile phase of phosphate buffer (pH 4.0):acetonitrile (70:30, v/v). Moperone was used as the internal standard. Haloperidol and moperone were detected with ultraviolet detection at 254 nm. The sensitivity was 5 ng/mL of milk, and the standard curve was linear in the concentration range 5-250 ng/mL. The average interassay coefficient of variation for samples with drug in the concentration range 25-125 ng/mL was less than 8.8%. The absolute recovery of haloperidol by the method was greater than 94.4%. No interference with endogenous substances in human milk was observed. The method was used to determine haloperidol levels in breast milk from patients undergoing chronic haloperidol treatment.     

Development, validation and application of the HPLC method for determination of mianserin in human serum

A high performance liquid chromatography method for the determination of mianserin in human serum was developed and validated. Doxepin was used as an internal standard. Mianserin was extracted from human serum using a liquid-liquid extraction with hexane:isoamyl alcohol (99:1, v/v). The sample was then dissolved in 0.05 M phosphoric acid (pH=3.0), and after separation on a Hichrom RPB (250 x 4.6 mm, 5 mm) column, the analytes were measured by ultraviolet detection at 214 nm. The recovery ranged from 86.1 to 94.5% for mianserin. The method was specific and linear over the concentration range of 2.0-128.0 ng/mL. The limit of quantification (LOQ) was established at 2.0 ng/mL (CV=13.8%). The accuracy range was from 92.5 to 107.5%. The method was used to measure mianserin in human serum samples obtained from healthy volunteers who had received a single oral dose of 30 mg mianserin. Pharmacokinetic parameters obtained for the mianserin were in agreement with the existing data.     

Simultaneous determination of albendazole metabolites, praziquantel and its metabolite in plasma by high-performance liquid chromatography-electrospray mass spectrometry

The analysis of albendazole sulfoxide, albendazole sulfone, praziquantel and trans-4-hydroxypraziquantel in plasma was carried out by high-performance liquid chromatography-mass spectrometry ((LC-MS-MS). The plasma samples were prepared by liquid-liquid extraction using dichloromethane as extracting solvent. The partial HPLC resolution of drug and metabolites was obtained using a cyanopropyl column and a mobile phase consisting of methanol:water (3:7, v/v) plus 0.5% of acetic acid, at a flow rate of 1.0 mL/min. Multi reaction monitoring detection was performed by electrospray ionization in the positive ion mode, conferring additional selectivity to the method. Method validation showed relative standard deviation (precision) and relative errors (accuracy) lower than 15% for all analytes evaluated. The quantification limit was 5 ng/mL and the linear range was 5-2500 ng/mL for all analytes. The method was used for the determination of drug and metabolites in swine plasma samples and proved to be suitable for pharmacokinetic studies.     

Quantitative determination of amantadine in human plasma by liquid chromatography-mass spectrometry and the application in a bioequivalence study

A sensitive liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method is developed and validated for rapid determination of amantadine in human plasma. Desloratadine was used as the internal standard (I.S.). Human plasma (0.2 mL) was first alkalified with 100 microL of sodium hydroxide (3M) and then extracted with 1 mL of n-hexane containing 1% isopropanol (v/v) and 10% dichloromethane (v/v) by vortex-mixer for 3 min. The mixture was centrifuged at 14,000 rpm for 5 min. The supernatant was evaporated to dryness and the residue was dissolved in mobile phase. Samples were separated using a Thermo Hypersil-HyPURITYC18 reversed-phase column (150 mm x 2.1 mm i.d., 5 microm). Mobile phase consisted of methanol-acetonitrile-20 mM ammonium acetate (45:10:45, v/v/v) containing 1% acetic acid with pH 4.0. Amantadine and I.S. were measured by electrospray ion source in positive selective ion monitoring mode. The good linearity ranged from 3.9 to 1000 ng/mL and the lowest limit of quantification was 3.9 ng/mL. The extraction efficiencies were approximately 70% and recoveries of method ranged from 98.53 to 103.24%. The intra-day relative standard deviations (R.S.D.) were less than 8.43% and inter-day R.S.D. below 10.59%. The quality control samples were stable when kept at room temperature for 12h, at -20 degrees C for 30 days and after four freeze/thaw cycles. The method has been successfully used to evaluation of the pharmacokinetics and bioequivalence of amantadine in 20 healthy volunteers after an oral dose of 100 mg amantadine.     

Liquid chromatography - tandem mass spectrometry for the simultaneous quantitation of glipizide, cilostazol and its active metabolite 3, 4-dehydro-cilostazol in rat plasma: application for a pharmacokinetic study

A liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) method for the simultaneous quantitation of glipizide, cilostazol and 3, 4-dehydro-cilostazol in rat plasma was developed and validated. Glimepride was used as an internal standard (IS). The analytes were extracted by using liquid-liquid extraction procedure and separated on a reverse phase C18 column (50 mm×4.6 mm i. d., 5 μ) using acetonitrile: 2 mM ammonium acetate buffer, pH 3.2 (90:10, v/v) as mobile phase at a flow rate 0.4 mL/min in an isocratic mode. Selective reaction monitoring was performed using the transitions m/z 446.4>321.1, 370.2>288.3, 368.3>286.2, and 491.4>352.2 to quantify glipizide, cilostazol, 3, 4-dehydro-cilostazol and glimepride, respectively. Calibration curves were constructed over the range of 25-2 000 ng/mL for glipizide, cilostazol and 3, 4-dehydro-cilostazol. The lower limit of quantitation was 25 ng/mL for all the analytes. The recoveries from spiked control samples were>76% for all analytes and internal standard. Intra and inter day accuracy and precision of validated method were within the acceptable limits of at all concentration. The quantitation method was successfully applied for simultaneous estimation of glipizide, cilostazol and 3, 4-dehydro-cilostazol in a pharmacokinetic drug-drug interaction study in wistar rats.     

Determination of mefunidone,a novel anti-fibrotic agent analogue of pirfenidone,in plasma by HPLC-UV and its pharmacokinetic application in rats

Mefunidone (MFD), a pirfenidone analogue, has been suggested as a novel anti-fibrotic agent in preclinical research stage. In this work, we developed a sensitive and specified HPLC-UV method and validated it for the determination of MFD in rat plasma. A cost-effective protein precipitation method using methanol was used to process the plasma samples, and pirfenidone was employed as the internal standard (IS). Chromatographic separation was performed on an Agilent ZORBAX SB-Aq column (4.6 mm×250 mm, 5 μm) with a mobile phase consisting of 10 mM ammonium formate solution (pH 3.0, adjusted by 1.5‰ formic acid)–acetonitrile–methanol (60:23:17, v/v/v) at a flow rate of 1.0 mL/min, and the samples were monitored at an ultraviolet wavelength of 245 nm. The retention times of MFD and IS were 5.5 and 7.8 min, respectively. The calibration curve was linear (r² = 0.9997) between 0.1 and 20 μg/mL. The intra- and inter-day precisions were within 8.6%, and the bias of intra- and inter-accuracies of the method was between –4.2% and 6.5%. The method was successfully applied to pharmacokinetic study of MFD after i.g. and i.v. administration in rats. The elimination half-life was (3.41±0.81) h for i.g. administration and (2.26±0.87) h for i.v. administration. The absolute bioavailability of MFD in rat was 79.1%.     

The PPARalpha/gamma dual agonist chiglitazar improves insulin resistance and dyslipidemia in MSG obese rats

1. The aim of this study was to investigate the capacity of chiglitazar to improve insulin resistance and dyslipidemia in monosodium L-glutamate (MSG) obese rats and to determine whether its lipid-lowering effect is mediated through its activation of PPARalpha. 2. Chiglitazar is a PPARalpha/gamma dual agonist. 3. The compound improved impaired insulin and glucose tolerance; decreased plasma insulin level and increased the insulin sensitivity index and decreased HOMA index. Euglycemic hyperinsulinemic clamp studies showed chiglitazar increased the glucose infusion rate in MSG obese rats. 4. Chiglitazar inhibited alanine gluconeogenesis, lowered the hepatic glycogen level in MSG obese rats. Like rosiglitazone, chiglitazar promoted the differentiation of adipocytes and decreased the maximal diameter of adipocytes. In addition, chiglitazar decreased the fibrosis and lipid accumulation in the islets and increased the size of islets. 5. Chiglitazar reduced plasma triglyceride, total cholesterol (TCHO), nonesterified fatty acids (NEFA) and low density lipoprotein-cholesterol levels; lowered hepatic triglyceride and TCHO contents; decreased muscular NEFA level. Unlike rosiglitazone, chiglitazar showed significant increase of mRNA expression of PPARalpha, CPT1, BIFEZ, ACO and CYP4A10 in the liver of MSG obese rats. 6. These data suggest that PPARalpha/gamma coagonist, such as chiglitazar, affect lipid homeostasis with different mechanisms from rosiglitazone, chiglitazar may have better effects on lipid homeostasis in diabetic patients than selective PPARgamma agonists.     

高效液相离子对色谱法测定糖尿病大鼠血浆中二甲双胍浓度及其药代动力学研究(英文)

本研究建立并验证了测定糖尿病大鼠血浆中二甲双胍浓度的高效液相色谱方法,以阿替洛尔为内标,加入10%高氯酸沉淀蛋白来制备血浆样品。色谱条件:AQ-C18极限色谱柱(250mm×4.6mm,5μm),流动相(pH5.05)为乙腈-水(31:69,v/v,水相中含有0.002M十二烷基磺酸钠,0.0125M磷酸二氢钾,0.015M三乙胺),流速1.0mL/min。二甲双胍在7.5-4000ng/mL范围内具有良好的线性关系(r>0.994),最低检测限(LLOQ)为7.5ng/mL,描述精密度的相对标准偏差(RSD)范围为1.87%-15.70%,准确度为93.98%-106.89%。二甲双胍和内标的回收率分别为95.40%和95.31%。不同实验条件下质控样品的稳定性相对偏差范围在±9.00%之内。该方法成功地运用到糖尿病大鼠单剂量灌胃10mg/kg二甲双胍后的药代动力学研究中,结果显示本研究采用AQ-C18极限色谱柱建立的离子对色谱法对强极性化合物如二甲双胍具有良好的分离效果。     

Determination of gemcitabine and its metabolite in human plasma using high-pressure liquid chromatography coupled with a diode array detector

AIM:Toestablishahighpressureliquidchromatography(HPLC)methodfordeterminationoftheconcentrationofgemcitabine(dFdC)anditsmetabolite(dFdU)inhumanplasma.METHODS:Plasma1.0mLspikedwithfloxuridineasaninternalstandardwasextractedwith3.0mLofmethanol-acetonitrile(v/v,1:9).Thesupernatantwasevapo-ratedat60oCandtheresiduewasreconstitutedwith0.5mLofthesolutionusedasthemobilephase.Aftercentrifugation,50μLofthesupernatantwasinjectedintotheHPLCsystem.SeparationwasachievedonaC18(4.6mm×250mm,5μm)c…     

Determination of clopidogrel metabolite (SR26334) in human plasma by LC-MS

A new, sensitive, specific and reproducible method for determination of clopidogrel metabolite (SR26334) in human plasma has been developed. After liquid-liquid extraction on Chem Elut cartridges with dichloromethane, samples were quantified using reversed-phase high performance liquid chromatography with mass detection. The determination was performed on a Luna C18, 3 microm (75 mmx4.6 mm i.d.) column with an acetonitrile-water-formic acid mixture (60:40:0.1, v/v/v) as a mobile phase. The flow rate was set at 0.2 mL/min. Repaglinide was chosen as an internal standard and the time of analysis was 12 min. For SR26334 the limits of detection and quantification were 7.5 ng/mL and 20 ng/mL, respectively, and the calibration curve was linear up to 3000 ng/mL. The extraction recovery of SR26334 from plasma was within the range of 85-90%. The method has been successfully used to study clopidogrel metabolite pharmacokinetics in healthy volunteers.     

Bioequivalence study of bromhexine by liquid chromatography-electrospray ionization-mass spectrometry after oral administration of bromhexine hydrochloride tablets

A simple, sensitive and specific liquid chromatography-electrospray ionization-mass spectrometry method was developed for the quantitative determination of bromhexine in human plasma. Sample preparation involved simple liquid-liquid extraction. Simvastatin was used as internal standard. The separation of the analyte, internal standard and possible endogenous compounds were accomplished on a Shim-pack ODS column (150 mm x 4.6 mm i.d., 5 microm) with methanol-water (98:2, v/v) as mobile phase. Detection was performed in positive selected ion monitoring (SIM) mode at m/z 264.1 (for bromhexine) and m/z 441.7 (for IS). The method was validated over the range of 0.5-60 ng/mL and the results were acceptable. The method could offer the advantages of shorter run time (5.5 min) and lower LLOQ (0.5 ng/mL) with a decreased plasma volume requirement (250 microL) and it had been successfully applied to a bioequivalence study in healthy Chinese volunteers after single oral administration of 16 mg bromhexine.     

液相质谱串联法同时测定舒尼替尼及其活性代谢产物SU12662在BABL/c裸鼠血浆中的浓度及其药物动力学研究(英文)

本研究建立并验证了一种灵敏、快速、简单的液质联用方法,用于同时测定BABL/c裸鼠血浆中舒尼替尼及其活性代谢产物SU12662的药物浓度。血浆样品采用蛋白沉淀方法处理,并使用帕唑帕尼作为内标。采用C18反相柱进行分离,流动相为10 mM甲酸胺–乙腈(65:35,v/v,pH 3.25),流速0.5 m L/min。所有化合物均采用电喷雾电离源,正离子方式检测。舒尼替尼及SU12662的最低定量下限均为0.5 ng/m L,线性范围均为0.5–1000 ng/m L(r>0.99)。该方法对舒尼替尼及SU12662的测定均具有良好准确度以及可靠的日内、日间精密度,方法稳定性良好,无明显基质效应。此方法成功用于BABL/c裸鼠口服20 mg/kg舒尼替尼的药物代谢动力学研究。     

Quantitative determination of azithromycin in human plasma by liquid chromatography-mass spectrometry and its application in a bioequivalence study

A sensitive, rapid liquid chromatographic-electrospray ionization mass spectrometric method for determination of azithromycin in human plasma was developed and validated. Azithromycin in plasma (0.2mL) was extracted with methyl tert-butyl ether-hexane (50:50, v/v), organic phase was transferred to another clear 1.5mL Eppendorf tube and evaporated to dryness at 40 degrees C and dissolved in mobile phase, samples were separated using a Thermo Hypersil HyPURITY C18 reversed-phase column (150mmx2.1mm i.d., 5microm), together with a mobile phase containing of 20mM ammonium acetate (pH 5.2)-acetonitrile-methanol (50:40:10, v/v/v) and was isocratically eluted at a flow rate of 0.2mL/min. Azithromycin and its internal standard, clarithromycin, were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 2 to 1000ng/mL with r=0.9977. The limit of quantification for azithromycin in plasma was 2ng/mL with good accuracy and precision. The higher mean extraction recovery, say 81.2% and 75.5% for azithromycin and internal standard (IS), respectively, was obtained in this work. The intra-day and inter-day precision ranged from 4.8% to 8.6% and 6.4% to 10.7% (R.S.D.), respectively. The established method has been successfully applied to bioequivalence study of 2 azithromycin formulations for 24 healthy volunteers.     

Development of characterization methods for entacapone in a pharmaceutical bulk

A comprehensive approach was taken to develop analytical procedures for the characterization of entacapone in a pharmaceutical bulk. A novel reversed-phase HPLC method was developed and validated for the assay of entacapone and the determination of impurities. The method employed a C18 column, a mobile phase of potassium phosphate buffer (pH 2.75, 30 mM)-methanol (50:50, v/v) at a flow rate of 1.0 mL/min, and ultraviolet (UV) detection at 310 nm. The method was linear over the range from 50% to 150% of the assay concentration (0.2mg/mL). The limit of quantitation was 0.13 μg/mL, and the limit of detection was 0.05 μg/mL. Average recovery was 100.10% with a relative standard deviation (N=9) of 0.45%. Degradation studies showed that entacapone eluted as a spectrally pure peak and was well resolved from its degradation products. The method was specific, sensitive, precise, linear, and accurate. UV and infrared spectroscopy (IR) were suitable as identification tests. The UV and FTIR spectra were acquired from a candidate reference standard and two commercial bulks. All materials exhibited maxima and minima at the same wavelengths. Water sorption analysis showed that entacapone was not affected by atmospheric moisture. These methods can be used for qualitative and quantitative analysis of entacapone in a pharmaceutical bulk.     

LC-MS determination and bioavailability study of imidapril hydrochloride after the oral administration of imidapril tablets in human volunteers

The purpose of the present study was to develop a standard protocol for imidapril hydrochloride bioequivalence testing. For this reason, a specific LC-MS method was developed and validated for the determination of imidapril in human plasma. A solid-phase extraction cartridge, Sep-pak C18, was used to extract imidapril and ramipril (an internal standard) from deproteinized plasma. The compounds were separated using a XTerra MS C18 column (3.5 microm, 2.1 x 150 mm) and acetonitrile-0.1% formic acid (67:33, v/v) adjusted to pH 2.4 by 2 mmol/L ammonium formic acid, as mobile phase at 0.3 mL/min. Imidapril was detected as m/z 406 at a retention time of ca. 2.3 min, and ramipril as m/z 417 at ca. 3.6 min. The described method showed acceptable specificity, linearity from 0.5 to 100 ng/mL, precision (expressed as a relative standard deviation of less than 15%), accuracy, and stability. The plasma concentration-versus-time curves of eight healthy male volunteers administered a single dose of imidapril (10 mg), gave an AUC12hr of imidapril of 121.48 +/- 35.81 ng mL(-1) h, and Cmax and Tmax values of 32.59 +/- 9.76 ng/mL and 1.75 +/- 0.27 h. The developed method should be useful for the determination of imidapril in plasma with sufficient sensitivity and specificity in bioequivalence study.