Liquid chromatographic assay of ivermectin in human plasma for application to clinical pharmacokinetic studies

There is a need for an accurate, sensitive and selective high-performance liquid chromatography (HPLC) method for the quantitation of ivermectin in human plasma that separates the parent drug from metabolites. Ivermectin and the internal standard, moxidectin, were extracted from 0.2 ml of human plasma using Oasis HLB solid phase extraction cartridges. After extraction, fluorescent derivatives of ivermectin and moxidectin were made by reaction with trifluoroacetic anhydride and N-methylimidazole. Separation was achieved on a Alltech Ultrasphere C18 5mu column with a mobile phase composed of tetrahydrofuran-acetonitrile-water (40:38:22 v/v/v). Detection is by fluorescence, with an excitation of 365 nm and emission of 475 nm. The retention times of ivermectin and internal standard, moxidectin are approximately 24.5 and 12.5 min, respectively. The assay is linear over the concentration range of 0.2-200 ng/ml of ivermectin in human plasma (r = 0.9992, weighted by 1/concentration). Recoveries of ivermectin are greater than 80% at all concentrations. The analysis of quality control samples for ivermectin 0.2, 25, and 200 ng/ml demonstrated excellent precision with coefficient of variation of 6.1, 3.6 and 2.3%, respectively (n = 6). The method is accurate with all intra-day (n = 6) and interday (n = 12) mean concentration within 10% of nominal values at all quality control sample concentrations. Storage stability for 30 days at -80 degrees C and after three freeze-thaw cycles are within acceptable limits. The method separates ivermectin from multiple less and more polar unidentified metabolites. This method is robust and suitable for clinical pharmacokinetic studies. The analytical procedure has been applied to a pharmacokinetic study of ivermectin in healthy volunteers and to the analysis of plasma specimens from patients with disseminated strongyloidiasis.     

Gas chromatographic assay of diethylcarbamazine in human plasma for application to clinical pharmacokinetic studies

A sensitive and selective gas chromatography method using flame ionization detection was developed for the determination of diethylcarbamazine (DEC) in human plasma. DEC and the internal standard, 1-diethylcarbamyl-4-ethyl piperazine HCl (E-DEC), were extracted from human plasma after loading onto a conditioned C(18) solid phase extraction cartridge, rinsed with water and eluted with methanol. After evaporation under a stream of nitrogen and reconstitution in methanol, 3 microl were injected onto the GC system. Separation was achieved on a A Heliflex(R) AT-35 capillary column (length 30 m, internal diameter 0.32 mm). Gas flow rates were: hydrogen, 35 ml/min; carrier gas (helium), 1.5 ml/min, make-up gas (helium), 25 ml/min; and air 420 ml/min. The retention times of DEC and internal standard were approximately 5.5 and 7.28 min, respectively. The GC run time was 22 min. The assay was linear in concentration range 100-2000 ng/ml for DEC in human plasma. The analysis of quality control samples for DEC (120, 1000, 2000 ng/ml) demonstrated excellent precision with coefficients of variation of 4.5,1.3, and 1.6%, respectively (n=6). The method was accurate with all intra-day (n=6) and inter-day (n=12) mean concentrations within 4.3% from nominal at all quality control sample concentrations. DEC was found to be stable after 3 freeze-thaw cycles, and with storage at -20 degrees C for 12 weeks. The method is currently being used for pharmacokinetic studies of DEC in healthy volunteers.     

Validation of a levofloxacin HPLC assay in plasma and dialysate for pharmacokinetic studies

An HPLC method with fluorescence detection suitable for routine determination of levofloxacin in plasma and dialysate has been validated. Sample preparation was assured by one-step protein precipitation for plasma or direct injection of the dialysate solution, respectively. Separation occurred on an YMC Pro C18 RP column (150 mm x 2 mm) with an acidic binary gradient mobile phase and detection at excitation and emission wavelengths of 296 and 504 nm. The assay was linear between 0.1 and 6 microg/ml for plasma and 0.1 and 5 microg/ml for dialysate with intra- and inter-day precision and accuracy lower than 10%. No degradation of levofloxacin was observed under the applied conditions for both matrices. The method was successfully applied to an in vitro pharmacokinetic study and patient samples as well.     

HPLC法测人血浆中丹皮酚浓度及其药代动力学研究

目的：建立HPLC丹皮酚胶囊血浓度测定方法，评价丹皮酚胶囊的药代动力学特点。方法：24名健康志愿者单剂量口服160mg丹皮酚胶囊，按设定时间采集肘静脉血经乙睛萃取处理，以XB—C18（250mm×4．6mm，5μm）色谱柱为固定相，四氢呋喃-甲醇-水-磷酸（6：60：34：0．1）为流动相测定丹皮酚血浆浓度。采用DAS2．0计算丹皮酚主要药动学参数。结果：丹皮酚线性范围10—500mg／mL，最低检出浓度为10ng／mL。主要药代动力学参数：Cmax为（116±46）ng／mL，tmax为（1．02±0．13）h，t1/2为1．03h。结论：建立的HPLC方法特异性强、灵敏度高，可用于丹皮酚血药浓度测定和人体药动学研究。     

HPLC法测人血浆对乙酰氨基酚浓度及其药代动力学研究

目的建立HPLC法测人血浆中对乙酰氨基酚浓度,并进行药代动力学研究.方法血浆样品采用液-液萃取法萃取,UltimateTM XB-C18(250mm×4.6mm,5μm)色谱柱分离;流动相为乙腈:水(10∶90,V/V),流速:1.0mL·min-1;检测波长237nm.结果对乙酰氨基酚血药质量浓度在0.025~25μg·mL-1内的线性关系良好(r=0.9989),血浆中低、中、高3种浓度(0.05,5,20μg·mL-1)的相对回收率在92.9%~92.1%之间;日内RSD≤5.77%,日间RSD≤4.24%.结论本法操作简便、准确、灵敏,适用于乙酰氨基酚的药动学研究.     

Liquid chromatographic assay of moxidectin in human plasma for application to pharmacokinetic studies

A sensitive and selective high-performance liquid chromatography (HPLC) method is presented for the analysis of moxidectin in human plasma. Solid phase extraction using Oasis HLB cartridges is used for sample preparation. The fluorescent derivative is obtained by a dehydrative reaction with trifluoroacetic anhydride and N-methylimidazole. Separation is achieved on a Bondapak C(18) reversed-phase column with a mobile phase composed of tetrahydrafuran-acetonitrile-water (40:40:20, v/v/v). Detection is by fluorescence, with excitation at 365 nm and emission at 475 nm. The retention times of moxidectin and internal standard, ivermectin are approximately 10.7 and 18.6 min, respectively. The assay is linear over the concentration range 0.2-1000 ng/ml for moxidectin in human plasma (r=0.9999, weighted by 1/concentration). Recoveries at concentrations 0.2, 400, 1000 ng/ml are 94, 75, and 71%, respectively. The analysis of quality control (QC) samples for moxidectin (0.2, 400, and 1000 ng/ml) demonstrates excellent precision with relative standard deviations of 11.9, 5.7, and 2.7%, respectively (n=6). The method is accurate with all intra- (n=6) and inter-day (n=18) mean concentrations within (5.0%) from nominal at all QC sample concentrations. Moxidectin was found to be stable after three free-thaw cycles, and with storage at -20 and -80 degrees C for 12 weeks. The method is suitable for pharmacokinetic studies of moxidectin after oral administration to humans.     

高效液相色谱法测定人体地尔硫及其主要代谢物的药物动力学

用高效液相色谱法（ＨＰＬＣ）测定人血清中地尔硫（ＤＺ）及去乙酰地尔硫（Ｍ１）浓度。以ＳｐｈｅｒｉｓｏｒｂＯＤＳ，５μｍ为层析柱，流动相：甲醇∶乙腈∶水（６０∶１０∶３０），检测波长２３７ｎｍ，以盐酸普罗帕酮为内标。检测范围：ＤＺ为５．４５～２７２．５ｎｇ·ｍｌ－１，Ｍ１为５．８５～２９２．５ｎｇ·ｍｌ－１。最低检测浓度：ＤＺ为２．８７ｎｇ·ｍｌ－１，Ｍ１为１．９９ｎｇ·ｍｌ－１。平均回收率ＤＺ为１０１．８８％，Ｍ１为１０１．７２％，ＲＳＤ均在１２％以内。并对４名受试者口服９０ｍｇ盐酸地尔硫片后，其药时曲线经微机用ＰＫＢＰ－Ｎ１程序拟合，ＤＺ为一房室开放模型，Ｍ１为二房室开放模型，求得ＤＺ和Ｍ１的Ｔ１／２分别为５．６±１．５ｈ和１４±７ｈ。     

头孢克洛血药浓度测定及其药代动力学研究

目的建立高效液相色谱法测定人血浆中头孢克洛浓度的方法。方法以头孢拉定为内标,采用DIS-COVERYC18色谱柱(4.6mm×250mm,5μm),以醋酸盐缓冲液-乙腈(83∶17)为流动相,流速:1mL/min;检测波长264nm。结果头孢克洛的线性范围为0.2～30μg/mL,回归方程为Y=0.0913X-0.0094,r=0.9996,最低检测浓度为0.1μg/mL,日内和日间RSD均小于7.5%。结论此法准确简便,适用于头孢克洛药代动力学的研究。     

Validated HPLC method for determination of amlodipine in human plasma and its application to pharmacokinetic studies

A rapid, simple and sensitive high-performance liquid chromatography (HPLC) method has been developed for quantification of amlodipine in plasma. The assay enables the measurement of amlodipine for therapeutic drug monitoring with a minimum detectable limit of 0.2 ng ml(-1). The method involves simple, one-step extraction procedure and analytical recovery was about 97%. The separation was performed on an analytical 125 x 4.6 mm i.d. Nucleosil C8 column. The wavelength was set at 239 nm. The mobile phase was a mixture of 0.01 M sodium dihydrogen phosphate buffer and acetonitrile (63:37, v/v) adjusted to pH 3.5 at a flow rate of 1.5 ml min(-1). The calibration curve was linear over the concentration range 0.5-16 ng ml(-1). The coefficients of variation for inter-day and intra-day assay were found to be less than 10%.     

Liquid chromatographic assay of nifedipine in human plasma and its application to pharmacokinetic studies

A highly sensitive, selective and reproducible reversed-phase high-performance liquid chromatographic method has been developed for the determination of nifedipine in human plasma with minimum sample preparation. The method is sensitive to 3 ng/ml in plasma, with acceptable within- and between-day reproducibilities and linearity (r2 > 0.99) over a concentration range from 10-200 ng/ml. Acidified plasma samples were extracted using diethyether containing diazepam as internal standard and chromatographic separation was accomplished on C18 column using a mobile phase consisting of acetonitrile, methanol and water (35:17:48, v/v). The within-day precision ranged from 2.22 to 4.64% and accuracy ranged from 102.4-106.4%. The day-to-day precision ranged from 2.34-7.07% and accuracy from 95.1-100.1%. The relative recoveries of nifedipine from plasma ranged from 91.0-107.3% whereas extraction recoveries were 88.6-93.3%. Following eight 6-week freeze-thaw cycles, nifedipine in plasma samples proved to be stable with accuracy ranging from 0.64 to 3.0% and precision ranging from 3.6 to 4.15%. Nifedipine was also found to be photostable for at least 120 min in plasma, 30 min in blood and for 60 min in aqueous solutions after exposure to light. The method is sensitive and reliable for pharmacokinetic studies and therapeutic drug monitoring of nifedipine in humans after the oral administration of immediate-release capsules and sustained-release tablets to five healthy subjects.     

HPLC method for the determination of fluvoxamine in human plasma and urine for application to pharmacokinetic studies

A simple, specific and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the assay of fluvoxamine in human plasma and urine. The method was based on reaction of fluvoxamine with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS) forming orange colored product. The fluvoxamine-NQ derivative was separated by isocratic reversed-phase HPLC and detected at 450 nm. The chromatographic conditions were as follows: Phenomenex C(18) (250 mm x 4.6 mm i.d., 5 microm) column, mobile phase consisting of acetonitrile/water (80:20 v/v) at a flow rate of 1 ml/min. Tryptamine was selected as an internal standard. The assay was linear over the concentration range of 5-145 and 2-100 ng/ml for plasma and urine, respectively. The limits of detection (LOD) were 1.4 and 1 ng/ml for plasma and urine estimation at a signal-to-noise (S/N) ratio of 3. The limits of quantification (LOQ) were 5 and 2 ng/ml for plasma and urine, respectively. The extraction recoveries were found to be 96.66+/-0.69 and 96.73+/-2.17% for plasma and urine, respectively. The intra-day and inter-day standard deviations (S.D.) were less than 1. The method indicated good performance in terms of specificity, linearity, detection and quantification limits, precision and accuracy. This assay was demonstrated to be applicable for clinical pharmacokinetic studies.     

simultaneous determination of mycophenolic acid and its metabolites by HPLC and pharmacokinetic studies in rat plasma and bile

In this study, we determined the pharmacokinetics of mycophenolic acid (MPA) and its metabolites mycophenolic acid glucuronide (MPAG) and acyl glucuronide (AcMPAG) in rat plasma and bile, using a newly developed HPLC method. Protein precipitation and liquid-liquid extraction were employed in sample preparation of plasma and bile, respectively. The HPLC methods included a gradient elution consisting of acetonitrile and phosphate buffer at a flow rate of 1.2 mL/min, with UV detection at 254 nm. The HPLC method was found to be sensitive and linear (r ² ≥ 0.9991, 1.0–128.0 and 0.25–32.0 mg/L for MPA; 1.0–128.0 and 0.5–64.0 mg/L for MPAG; 0.25–32.0 and 1.0–128.0 mg/L for AcMPAG in rat plasma and bile, respectively), precise (both the intra- and inter-day variability were ≤ 6.8%), and accurate (both the intra- and inter-day accuracy were between 92.2% and 105.4%). The average extraction efficiencies for MPA, MPAG and AcMPAG were 85.3%, 100.1%, and 94.7% in plasma, and 88.0%, 67.3%, and 68.3% in bile, respectively. The method was successfully employed for pharmacokinetic studies in plasma and bile after oral administration of mycophenolate mofetil (prodrug of MPA) in rats.     

A rapid HPLC assay for voriconazole in human plasma

This report describes a simple, rapid and reproducible method with a calibration range of 0.2–10 μg ml⁻¹ voriconazole in human plasma which is more appropriate for routine clinical use than the authors previously published method. The method utilises protein precipitation with acetonitrile as the only sample preparation involved prior to reverse phase HPLC. No internal standard was required.     

HPLC法测定人血浆中奥沙普秦含量及其药物动力学

目的建立HPLC法测定人血浆中奥沙普秦(oxaprozin,Oxa)浓度的方法,并研究其在健康受试者体内的药物动力学。方法采用固相萃取法提取样品,以布洛芬为内标物,采用Diamonsil-C18(150 mm×4.6 mm,5μm)色谱柱,流动相为甲醇-20 mmol·L-1醋酸铵水溶液(pH=3.0±0.2)(体积比为63∶27),流速为1.0 mL·min-1,柱温为30℃,检测波长为280 nm。结果 Oxa在0.5¹50.0 mg·L-1内与峰面积呈良好线性关系(r=0.996 9),日间和日内精密度RSD均小于6.5%,提取回收率大于68.4%。主要药物动力学参数为:ρmax(84±12)mg·L-1,tmax(3.2±1.4)h,t1/2(49±4)h,AUC0→t(2 383±327)mg·h·L-1,AUC0→∞(2 468±346)mg·h·L-1。结论 HPLC法适用于临床测定奥沙普秦在人体中的浓度。     

HPLC method for the determination of rosiglitazone in human plasma and its application in a clinical pharmacokinetic study

Rosiglitazone (CAS 155141-29-0, Avandia) is a novel insulin sensitizer used in the treatment of type 2 diabetes. A sensitive high performance liquid chromatography (HPLC) method for its determination in human plasma using fluorescence detection (excitation: 247 nm, emission: 367 nm) with a suitable internal standard (I. S.) is described. Ethyl acetate was used as extraction solvent. A mobile phase consisting of phosphate buffer, acetonitrile and methanol was used at a flow rate of 1.0 ml/min on a C18 column. The absolute recovery was > 90% and the lower limit of quantitation was 5 ng/ml. The intra- and inter-day relative standard deviations ranged from 0.58-6.69% and 0.82-6.63%, respectively. The method described is simple, economical, precise and accurate and has been successfully applied in a pharmacokinetic study conducted in healthy human volunteers.     

Analysis of nabumetone in human plasma by HPLC. Application to single dose pharmacokinetic studies

A simple and sensitive high performance liquid chromatography method for the determination of nabumetone in human plasma is described. The procedure involves liquid-liquid extraction with ethyl acetate and reversed-phase chromatography with fluorimetric detection (excitation 230 nm, emission 356 nm). The chromatographic conditions and the extraction procedure gave a clean chromatogram for the compound. The limit of quantitation was established as 0.313 ng/ml and the calibration curve was linear up to 20 ng/ml. The within-day and between-day relative standard deviations were less than 10% and the accuracy of the assay was in the range of 99-104%. The suitability of the method is shown for pharmacokinetic studies.     

Method development and validation of repaglinide in human plasma by HPLC and its application in pharmacokinetic studies

In this study, the development and validation of a high-performance liquid chromatography (HPLC) assay for determination of repaglinide concentration in human plasma for pharmacokinetic studies is described. Plasma samples containing repaglinide and an internal standard, indomethacin were extracted with ethylacetate at pH 7.4. The recovery of repaglinide was 92% ± 55.31. Chromatographic separations were performed on Purospher^® STAR C-18 analytical column (4.8 mm × 150 mm; 5 μm particle size). The mobile phase composed of acetonitrile–ammonium formate (pH 2.7; 0.01 M) (60:40, v/v). The flow rate was 1 ml/min. The retention time for repaglinide and indomethacin were approximately 6.2 and 5.3 min, respectively. Calibration curves of repaglinide were linear in the concentration range of 20–200 ng/ml in plasma. The limits of detection and quantification were 10 ng/ml and 20 ng/ml, respectively. The inter-day precision was from 5.21 to 11.84% and the intra-day precision ranged from 3.90 to 6.67%. The inter-day accuracy ranged 89.95 to 105.75% and intra-day accuracy ranged from 92.37 to 104.66%. This method was applied to determine repaglinide concentration in human plasma samples for a pharmacokinetic study.     

离子对液相色谱法测定人血浆中替米沙坦的浓度及药动学研究

目的建立测定人血浆中替米沙坦浓度的高效液相色谱方法,并用该法研究替米沙坦片在健康人体内的药动学。方法色谱柱为Sh im-pack VP-ODS(150mm×4.6mm),流动相为乙腈-0.05%戊磺酸钠-0.05 mol.L-1磷酸二氢钾(50∶25∶25),荧光检测,激发波长为305nm,发射波长为365nm。结果血浆样品在3.05~610.0μg.L-1内线性相关(r=0.9999,n=5)。平均绝对回收率为85.1%(RSD=1.63%),相对回收率大于95.0%,日间和日内相对标准差小于10.0%。10名男性健康志愿者单次口服80mg替米沙坦片后,其药代动力学参数分别为:t1/2(19.8±5.66)h,cm ax(310.7±91.6)μg.L-1,tm ax(1.01±0.40)h。结论此方法准确,灵敏,适于体内药物分析;药动学参数为临床合理用药提供理论依据。     

An efficient HPLC method for the quantitative determination of atazanavir in human plasma suitable for bioequivalence and pharmacokinetic studies in healthy human subjects

An efficient HPLC method for the determination of atazanavir in human plasma has been developed and validated. A relatively simple mobile phase consisting of acetonitrile–ammonium formate buffer (pH 3; 10 mM) (45:55, v/v) was pumped at a low flow rate of 0.3 ml/min through a reverse phase Phenomenex^® Luna C18 (2) (5 μm, 150 mm × 2.0 mm i.d.) column maintained at 30 °C. Diazepam was used as an internal standard and the eluent was monitored at 210 nm. The major advantage of this method over previously reported procedures is that the narrow-bore HPLC column used resulted in relatively short retention times for the internal standard (6.8 min) and atazanavir (8.3 min) with excellent peak resolution and associated reduction in solvent usage. Sample preparation involved liquid–liquid extraction using 400 μl plasma treated with sodium carbonate (2 M) and extracted with a mixed organic solvent consisting of ethyl acetate–n-hexane (50:50, v/v). The organic layer was removed and evaporated to dryness under nitrogen. Samples were reconstituted in mobile phase (100 μl) and 20 μl was injected onto the column. The procedures were validated according to international standards with good reproducibility and linear response with correlation coefficients (r) consistently ≥0.999. The intra- and inter-day accuracies were 97.1 ± 5.04 and 98.0 ± 11.3 respectively at the LLOQ and between 101 ± 4.48% and 104 ± 2.09% for the QC samples. The intra- and inter-day precision were ≤11.6% RSD at the LLOQ and ≤6.78% RSD across the entire QC concentration range. Mean recovery based on high, medium and low quality control standards ranged between 94.4 ± 1.07% and 100 ± 2.22%. Plasma samples were evaluated under short-term (ambient temperature for 6 h) and long-term (−10 ± 2 °C for 2 months) storage conditions and were found to be stable. The method described is efficient and has the necessary accuracy and precision for the rapid quantitative determination of atazanavir in human plasma and is thus highly suitable for use in pharmacokinetic/bioavailability/bioequivalence studies in healthy human subjects.