LC Determination of Helicidum in Beagle Dog Plasma: Study on the Pharmacokinetics of Helicidum Orally Disintegrating Tablets Compared to Conventional Tablets

A sensitive and reproducible liquid chromatographic method with UV detection was described for the determination of helicidum in beagle dog plasma. Sample preparation was accomplished through protein precipitation with 15% perchloric acid and chromatographic separation was performed on a reversed phase C₁₈ column at 30 °C. Mobile phase consisted of a mixture of acetonitrile–water at a flow rate of 1.0 mL min⁻¹. Wavelength was set at 270 nm. The method was applied to a pharmacokinetic study of two formulations of helicidum. No statistical difference in the t _1/2 (AUC_0–5, AUC_0–∞) between the two formulations were observed. The t _max of helicidum ODTs is significantly shorter than that of conventional tablets (0.84 h vs. 1.33 h, P< 0.05).

     

LC Determination and Pharmacokinetic Study of Sinomenine in Dog Plasma

A simple HPLC method has been developed for determination of sinomenine in dog plasma and has been used to evaluate the pharmacokinetics of sinomenine tablets in dogs. Chromatographic separation was performed on a reversed-phase column with 0.78% (w/v) NaH₂PO₄-acetonitrile, 88:12 (v/v), as mobile phase, delivered at a flow rate of 1.5 mL min^?1. Detection was performed at 265 nm. The limit of quantification was 5.0 ng mL^?1. The calibration range was from 5.0 to 1000 ng mL^?1. The developed method was applied to pharmacokinetic studies of sinomenine sustained-release tablets (test preparation) and sinomenine conventional tablets (reference preparation) in six dogs. Pharmacokinetic data t _max, C _max, AUC _0-t , AUC _0-∞, and t _1/2 for both preparations were determined from plasma concentration-time profiles. The method was sufficiently sensitive, simple, and repeatable for use in pharmacokinetic studies.     

LC Determination of Curcumin in Dog Plasma for a Pharmacokinetic Study

A rapid, simple, and sensitive high-performance liquid chromatographic method for quantification of curcumin in dog plasma has been developed and validated. After addition of the internal standard (berberine), plasma was acidified and extracted with ethyl acetate. Analysis was performed on a C₁₈ column. The mobile phase was acetonitrile–5% acetic acid, 52:48 (v/v) and the flow rate 1.0 mL min^?1. The eluent was monitored at 425 nm. Chromatographic separation was achieved in less than 7 min and the calibration plot was linear over the concentration range 2–128 ng mL^?1. Intra- and inter-assay variability were less than 7.3%. The accuracy ranged from 98.7 to 105.0%. The method was successfully applied to a pharmacokinetic study of curcumin in dogs.     

LC Determination and Pharmacokinetics Study of Mangiferin in Rat Plasma and Tissues

An LC method was developed for determination of mangiferin in rat plasma and tissues after oral administration of Rhizoma Anemarrhenae extract. Analysis was performed on a Gemini C₁₈ analytical column (250 × 4.6 mm, i.d.) with mobile phase consisting of acetonitrile–water (23:77, v/v) with 1% acetic acid and 1% tetrahydrofuran at a flow rate of 0.7 mL min⁻¹. Spinosin was used as internal standard and UV detector was set at 320 nm. The calibration curve of mangiferin in rat plasma and tissues showed excellent linear behaviors over the investigated concentration ranges with the value of R ² higher than 0.994. The within-day and between-day precisions for all samples were measured to be below 11.0%. The limit of quantitation was low enough for determination of mangiferin in all samples. After Rhizoma Anemarrhenae extract was orally administered to rats, the main pharmacokinetic parameters of mangiferin T _max, C _max, T _0.5α , T _0.5β , AUC_0 − T and Vc were 4.20 h, 9.52 μg mL⁻¹, 1.21 h, 1.71 h, 29.9 mg h L⁻¹ and 0.18 L kg⁻¹, respectively. Mangiferin was extensively distributed in most of the main tissues of rats. This validated method has been successfully applied to preliminary pharmacokinetics and tissue distribution study of mangiferin in rats.

     

LC Determination and Pharmacokinetics Study of Mangiferin in Rat Plasma and Tissues

An LC method was developed for determination of mangiferin in rat plasma and tissues after oral administration of Rhizoma Anemarrhenae extract. Analysis was performed on a Gemini C₁₈ analytical column (250 × 4.6 mm, i.d.) with mobile phase consisting of acetonitrile–water (23:77, v/v) with 1% acetic acid and 1% tetrahydrofuran at a flow rate of 0.7 mL min^?1. Spinosin was used as internal standard and UV detector was set at 320 nm. The calibration curve of mangiferin in rat plasma and tissues showed excellent linear behaviors over the investigated concentration ranges with the value of R ² higher than 0.994. The within-day and between-day precisions for all samples were measured to be below 11.0%. The limit of quantitation was low enough for determination of mangiferin in all samples. After Rhizoma Anemarrhenae extract was orally administered to rats, the main pharmacokinetic parameters of mangiferin T _max, C _max, T _0.5α , T _0.5β , AUC_0 ? T and Vc were 4.20 h, 9.52 μg mL^?1, 1.21 h, 1.71 h, 29.9 mg h L^?1 and 0.18 L kg^?1, respectively. Mangiferin was extensively distributed in most of the main tissues of rats. This validated method has been successfully applied to preliminary pharmacokinetics and tissue distribution study of mangiferin in rats.     

RP-HPLC Determination of Linarin in Beagle Dog Plasma After Administration of Yejuhua Injection

A sensitive, simple, and accurate reversed-phase column liquid chromatographic (RP-LC) method with daidzein as an internal standard and UV detection at 348 nm has been developed for determination of linarin in beagle dog plasma. Plasma protein was precipitated by addition of acetonitrile and the remaining solution was evaporated to dryness. The resulting residue was then reconstituted in methanol and injected on to a 250 mm × 4.6 mm i.d., 5 μm particle, ODS analytical column. The mobile phase was a gradient prepared from acetonitrile and an aqueous solution (0.4%) of phosphoric acid; the flow rate was 1.0 mL min⁻¹. Response was a linear function of concentration over the range 3.4–1,373.3 ng mL⁻¹; the correlation coefficient (R ²) was 0.993. Mean recovery was 74.2%. Within-day and between-day precision were better than 8.8% relative standard deviation (RSD). The limit of quantification was 3.4 ng mL⁻¹. This RP-LC method was used successfully in pharmacokinetic studies of linarin in beagle plasma after administration of Yejuhua injection.     

LC Determination of Gemfibrozil in Tablets

A simple, selective, precise and accurate reversed phase-HPLC assay for analysis of gemfibrozil in tablets was developed and validated. Separation and quantification were achieved on a Phenomenex C₁₈ column under isocratic conditions using a mobile phase (methanol:water, 80:20, v/v) maintained at 1.1 mL min⁻¹. UV-detection was at 280 nm. Atorvastatin was selected as an internal standard. The standard curves were linear over the range of 0.5–3.0 μg mL⁻¹ (r > 0.999). The limits of detection and quantification were 0.20 and 0.51 μg mL⁻¹, respectively. The recoveries for gemfibrozil were above 99.01%. The intra-day and inter-day precision (RSD) for gemfibrozil were below 1.74 and 1.83%, respectively. No chromatographic interferences from the tablet excipients were found. The results of the developed procedure in tablets were compared with those of the reference method to assess gemfibrozil content. Statistical comparison of the results with the reference method using spectrofluorimetric method showed excellent agreement and proved no significant difference in accuracy and precision. This HPLC method is fast and simple for the analysis of gemfibrozil in pharmaceutical preparations.     

Liquid Chromatography-electrospray Ionization Tandem Mass Spectrometry for Simultaneous Determination of Metformin and Glimepiride in Beagle Dog Plasma and Bioequivalence Study

A sensitive and selective liquid chromatography-electrospray ionization tandem mass spectrometry(LCESI- MS/MS) was used for the simultaneous determination of metformin and glimepiride in beagle dog plasma with glipizide as internal standard(IS). After simplified protein precipitation with methanol, both the analytes and IS were chromatographed on a Zorbax CN column via gradient elution with methanol(containing 5 mmol/L ammonium acetate) and 5 mmol/L aqueous ammonium acetate as the mobile phase. Detection was performed by multiple reaction monitoring(MRM) scanning via ESI source operated in positive ionization mode. Specificity, linearity, accuracy, precision, recovery, matrix effect and stability were validated for metformin and glimepiride in beagle dog plasma. The calibration curves were linear in a concentration range of 10―10000 ng/mL for metformin and 4―4000 ng/mL for glimepiride with both correlation coefficients higher than 0.99. The recoveries obtained for the analytes and IS were all between 82.7% and 101.2%. The method exhibited excellent performance in terms of selectivity, robustness, short analytical time and simplicity of sample preparation. Finally, the proposed method was applied to a bioequivalence study of self-made bilayer tablet and commercial formulation containing 500 mg of metformin and 1 mg of glimepiride in beagle dogs.     

Stability-Indication LC Determination of Entacapone in Tablets

A rapid and sensitive RP-HPLC method with UV detection at 305 nm for routine quality control of entacapone in tablets was developed. The procedure was validated by specificity, robustness, linearity, accuracy, repeatability and intermediate precision. Experimental design was used during validation to calculate method robustness. The method employs an Ace RP-18 (250 × 4.6 mm i.d., particle size 5 μm), with a mobile phase consisting of water pH 3.0: acetonitrile (65:35, v/v). Entacapone solutions were exposed to direct UV radiation (254 nm), alkaline hydrolysis, acid hydrolysis and effect of oxidation by hydrogen peroxide to evaluate method stability-indication and peak purity tool was utilized to verify the peak purity. The results confirm that the method is highly suitable for its intended purpose.     

Validated LC Determination of the Piroxicam-β-Cyclodextrin Inclusion Complex in Tablets and in Human Plasma

A simple, rapid, specific, sensitive HPLC method has been developed for the determination of piroxicam in the tablet dosage form and in human plasma. The method totally eliminates solvent extraction and time-consuming separation procedures. Plasma proteins were precipitated by addition of 3:1 (v/v) acetonitrile-methanol, ZnSO₄, and MgSO₄ and the supernatant was injected directly on to a 250 mm × 4.6 mm, 5 μm particle Spherisorb analytical column. Acetonitrile-methanol-0.04 mol L^?1 KH₂PO_4, 40:10:50 (v/v); pH 3.8, was used as mobile phase. The drug was detected by UV detection at 330 nm. The response was linear over the range of 0.01–10 μg mL^?1 and 0.025–5 μg mL^?1 in mobile phase and human plasma samples, respectively. The proposed method was used without interference from the endogenous substances, for determination of piroxicam in plasma samples obtained from healthy volunteers. The results revealed that the method would be useful in monitoring plasma levels of the drug during pharmacokinetic studies. Assay of piroxicam in its dosage forms for quality-control purposes could also be performed successfully by use of this method.     

超高效液相色谱-串联质谱法测定犬血浆中利培酮和帕潘立酮及药代动力学研究

建立了超高效液相色谱-串联质谱法(UPLC-MS/MS)测定犬血浆中利培酮和帕潘立酮的浓度.血浆样品用乙腈沉淀蛋白后,用Zorbax SB-C18柱分离,以乙腈-10 mmol/L乙酸铵溶液(65∶35,V/V)为流动相,在电喷雾离子源正离子模式下以多反应监测(MRM)方式进行检测.利培酮、帕潘立酮分别在0.05～30.0 ng/mL和0.10～30.0 ng/mL范围内线性关系良好(r2＞0.99),定量限分别为0.05 ng/mL和0.10 ng/mL,回收率分别为91.2％～95.1％和93.1％～97.5％.该方法精密、准确、快速,适用于临床血药浓度的监测及利培酮缓释微球药动学的研究.     

尺寸排阻色谱-电感耦合等离子体质谱联用研究比格犬血浆中米铂及铂代谢物形态

建立了基于尺寸排阻色谱-电感耦合等离子体质谱联用( SEC-ICP-MS)分析比格犬血浆中米铂及其铂代谢物形态的方法。半定量测得的血浆中总铂的含量与传统ICP-MS直接测定方法基本相同。采用Bio-Sep-s2000型色谱柱在25 mmol/L磷酸盐缓冲液(pH 7.2)的色谱条件下与ICP-MS联用检测同位素Pt-195发现,血浆中有米铂原型和4种铂代谢物;将不同时间点采集的血浆进行铂形态分析发现,与蛋白结合的铂代谢物m2含量最高;米铂不与血浆蛋白结合。对比米铂与m2的相对含量发现,米铂原型与m2的比例在给药初期迅速下降,后缓慢上升,再随血药浓度的下降而缓慢下降。     

LC Determination and Bioequivalence Study of Pantoprazole in Human Plasma

A selective and sensitive liquid chromatography (LC) method with rapid sample processing was developed for determination of pantoprazole in human plasma using omeprazole as internal standard (IS). The plasma sample (100 μL) was deproteined by precipitation with methanol. The supernatant was directly determined by LC using a Diamonsil C₁₈ ODS column and solution of 10 mM Na₂HPO₄ buffer (containing 0.01% H₃PO₄) and acetonitrile (68:32, v/v, pH = 6.8) as mobile phase with UV detector set at 288 nm. The retention time of IS and pantoprazole were 4.9 ± 0.2 and 5.6 ± 0.2 min, respectively. The method was validated with a linear range of 0.03–5.0 μg mL^?1 and the lowest limit of quantification was 0.03 μg mL^?1 for pantoprazole (r = 0.9999). The coefficient of variation for intra-day and inter-day accuracy and precision was less than 9.5%. The mean extraction recovery was 84.1%. Quality control samples were stable when kept at autosampler temperature for 24 h, at ?20 °C for 42 days and after three freeze-thaw cycles. The assay was successfully applied to a randomized, two-period cross-over bioequivalence study in 20 healthy Chinese volunteers following a single oral dose of 40 mg pantoprazole. Various pharmacokinetic parameters including AUC _0～t , AUC _0～∞, C _max, T _max and t _1/2 were determined from plasma concentration of both formulations. The results indicated that the analytical method was a specific, precise, sensitive and rapid procedure for determination of plasma pantoprazole concentration and therefore, a suitable and valuable tool in the investigation of the clinical pharmacokinetics and bioequivalence.     

LC Determination and Pharmacokinetic Study of Gemfibrozil in Human Plasma

A simple and sensitive LC method for the quantitative determination of gemfibrozil in human plasma samples is described. Mometasone furoate was used as the internal standard. Plasma samples were pretreated by protein precipitation using methanol. Separation was performed at 40 °C on a YMC^® ODS-A reverse phase column (5 μm particle size, 150 mm × 4.6 mm i.d.) using 0.2% (v/v) triethylamine in water (adjusting to pH 4.0 with phosphoric acid) and acetonitrile (45:55, v/v) as mobile phase which was delivered at 1.5 mL min^?1. Ultraviolet detection was performed at 230 nm. The linear concentration range for gemfibrozil was 0.25–50 μg mL^?1. The detection limit of this method was 0.1 μg mL^?1. Intra- and inter-assay RSD ranged from 0.63 to 2.04% and 1.37 to 4.27%, respectively. The method was sensitive, simple and repeatable enough to be used in pharmacokinetic studies.     

HPLC Analysis and Pharmacokinetics of Picroside I in Dog Plasma

A sensitive and selective HPLC–UV method established for determination of picroside I in dog plasma has been used to study the pharmacokinetics of the drug after intravenous administration of three different doses. Sample pretreatment consists in deproteination by addition of acetonitrile; l-ascorbic acid was used to improve the stability of picroside I. The lower limit of quantification of picroside I was 0.05 μg mL⁻¹. The recovery of the method was up to 90%. After intravenous administration to dogs picroside I was mainly distributed in the central compartment and was rapidly eliminated from the plasma; the mean elimination half-life was 30.54 ± 4.34, 30.20 ± 3.78, and 34.02 ± 1.88 min for doses of 2.5, 5, and 15 mg kg⁻¹, respectively, and the respective values of AUC _0–∞ were 81.04 ± 19.95, 198.50 ± 27.77, and 586.44 ± 103.08 μg min mL⁻¹. The different doses had no significant effect on the main pharmacokinetic data and the kinetics seemed to be linear in dosage range 2.5–15 mg kg⁻¹.     

Development and Validation an LC Method for the Determination of Bendroflumethiazide in Human Plasma and its Pharmacokinetics

A simple, rapid, sensitive high performance liquid chromatography method with fluorescent detection was developed and validated for the determination of bendroflumethiazide in human plasma. Extraction from the plasma was by liquid-liquid extraction using ethyl acetate. Mosapride citrate was used as the internal standard. The chromatographic separation was performed on reverse phase LiChrosphere C18 column with mobile phase comprising of acetonitrile and phosphate buffer (38:62 v/v). The assay precision ranged from 0.9–12.5 and accuracy between 96.8–108.8%, revealing that the method has good reproducibility over the concentration range of 0.98–100.16 ng mL⁻¹. The validated method has been applied to analyze the bendroflumethiazide concentrations for application in pharmacokinetic, bioavailability or bioequivalence studies.     

Determination of Penciclovir in Human Plasma Using LC with Fluorescence Detection: Application to a Bioequivalence Study

A novel HPLC method with fluorescence detection and one step sample preparation was developed for the determination of penciclovir in human plasma. Plasma samples (200 μL) were deproteinized by precipitation with 100 μL of perchloric acid and centrifuged. Separation was on an Inertsil ODS-3 column with a mixture of methanol–0.1% orthophosphoric acid as mobile phase. The fluorescence detector was set at Ex 270 nm, Em 375 nm. The assay was selective and linear with a limit of quantification of 0.025 mg L^?1. The mean absolute recovery was 98.1%, while the intra- and inter-day coefficients of variation and percent error values of the assay method were all less than 10%. The assay was successfully applied in a randomized cross-over bioequivalence study of three pharmaceutical products containing 250 mg famciclovir (an oral prodrug of penciclovir) in 18 healthy volunteers.     

LC Determination of Icariside II in Rat Plasma and Tissues: Application to a Tissue Distribution Study

A sensitive and reliable reversed-phase liquid chromatography (RP-LC) with ultraviolet (UV) detection has been developed and validated for the quantification of Icariside II in rat plasma and tissues using Fermononetin as the internal standard. Protein precipitation and liquid?Cliquid extraction were utilized for plasma and tissue sample preparation, respectively. The analysis was successfully carried out on an Agilent SB-C₁₈ column (5 ??m, 4.6 × 250 mm) with the implementation of the following conditions: a mobile phase of phosphoric acid solution (0.1%, v/w)?CAcetonitrile (55:45, v/v), a flow rate of 1 mL min^?1, a column temperature of 25 °C and a detection wavelength of 270 nm. Good linear relationships of calibration curves were obtained (r ² > 0.9906) over the investigated concentration range with plasma and tissue samples. The lower limit of quantification (LLOQ) and the limit of detection (LOD) were 0.1 and 0.02 ??g g^?1, respectively (for plasma sample, they were 0.05 and 0.1 ??g mL^?1, respectively). The developed method which was embodied with good precision, accuracy, recovery and stability was corroborated to satisfy the requirements for biomedical sample analysis. This method has been successfully applied to tissue distribution study of Icariside II in rats after a single intravenous dose at 12.5 mg kg^?1. Results suggested that Icariside II was distributed to rat tissues rapidly with greater initial concentrations in kidney, lung and liver. Moderate initial distributions were obtained in rat muscle, heart, bone, spleen and plasma. Low amount of Icariside II was detected in testes, and no Icariside II could be detected in the brain.     

UPLC for the Determination of Clopidogrel in Dog Plasma by Tandem Quadrupole MS: Application to a Pharmacokinetic Study

A rapid, sensitive and specific ultra performance liquid chromatography-electrospray ionization tandem quadrupole mass spectrometry method was developed and validated for the determination of clopidogrel in dog plasma. Plasma samples were deproteinized with acetonitrile and separated on a Waters BEH C18 column (1.7 μm, 50 mm × 2.1 mm id.) with isocratic elution at a flow-rate of 0.2 mL min^?1 and mobile phase consisting of acetonitrile and water (containing 0.15% formic acid) (75:25, v/v). The single run analysis was as shorter as 2 min. Electrospray ionization in positive ion mode and multiple reaction monitoring were used for the quantification of clopidogrel with monitored transitions m/z 322 → 212 for clopidogrel and m/z 324 → 217 for internal standard (gliclazide). The intra- and inter-day precisions (RSD%) were less than 6.32 and 7.03%, and accuracy (RE%) between ?9.12 and 9.65% (n = 6). The extraction recovery of clopidogrel was 96.7%. The developed method was successfully applied to the pharmacokinetic study of clopidogrel tablets in dogs following oral administration at a single dose of 75 mg.