Therapeutic drug monitoring of the HIV/AIDS drugs abacavir, zidovudine, efavirenz, nevirapine, indinavir, lopinavir, and nelfinavir

Combination therapy with antiretroviral drugs is used for the treatment of patients infected with the human immunodeficiency virus. To achieve optimal drug concentrations for viral suppression and avoidance of drug toxicity, monitoring of drug levels has been considered essential. We set up an analytical procedure for monitoring the plasma concentrations of a total of seven drugs: abacavir, zidovudine, efavirenz, nevirapine, indinavir, lopinavir, and nelfinavir. The plasma samples were liquid/liquid extracted and subjected to high-performance liquid chromatography (HPLC) analysis. The compounds were monitored by ultraviolet detection: indinavir, lopinavir, and nelfinavir at 215 nm; efavirenz at 254 nm, and abacavir, zidovudine, and nevirapine at 266 nm. Two different extraction procedures and two different HPLC eluents on a C(8) reversed-phase HPLC column were used to monitor all seven compounds. Under steady state conditions, the plasma concentrations of antiviral drugs in 175 patients were correlated with the time after the last dosing to define the peak or trough levels. Due to the short plasma elimination half-life of abacavir and zidovudine, only peak levels could be determined for these compounds, whereas both peak and trough levels could be assessed for the other compounds because of a longer plasma elimination half-life. The mean peak concentrations (microg/ml) were 0.69 for abacavir and 0.57 for zidovudine; the mean peak/trough concentrations (microg/ml) were 2.07/1.32 for efavirenz, 2.43/2.23 for nevirapine, 5.48/1.08 for indinavir, 4.69/3.51 for lopinavir, and 3.54/1.45 for nelfinavir. The described analytical method offers a broad-spectrum monitoring of plasma levels of antiretroviral drugs.     

Quantitation of acetazolamide in rat plasma, brain tissue and cerebrospinal fluid by high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatographic method for the analysis of acetazolamide (AZ) in rat blood (plasma/serum, whole blood and serum ultrafiltrate), brain tissue and cerebrospinal fluid (CSF) was described. Quantitative extraction of AZ with ethyl acetate from both buffered plasma and brain tissue homogenate (pH 8.0) was achieved. Each extract was evaporated to dryness and the residue was chromatographed on a reversed-phase column. CSF was directly analysed without extraction step. The limits of detection were 0.05 μg ml⁻¹ for plasma, 0.02 μg g⁻¹ for brain tissue and 0.004 μg ml⁻¹ for CSF. Calibration curves were linear over the working ranges of 0.1–100 μg ml⁻¹ for plasma, 0.05–50 μg g⁻¹ for brain tissue and 0.025–50 μg ml⁻¹ for CSF. The reproducibility of AZ assay in the rat biologic media indicated very low relative standard deviations (RSDs). The recoveries of AZ added to plasma and brain tissue were more than 96% with an RSD of less than 5%. The present method was applied to studies of plasma concentration profiles of the drug after administration and its distribution into central nervous system.     

Midazolam microdose to determine systemic and pre-systemic metabolic CYP3A activity in humans

Aim

We aimed to establish a method to assess systemic and pre-systemic cytochrome P450 (CYP) 3A activity using ineffective microgram doses of midazolam.

Methods

In an open, one sequence, crossover study, 16 healthy participants received intravenous and oral midazolam at microgram (0.001 mg intravenous and 0.003 mg oral) and regular milligram (1 mg intravenous and 3 mg oral) doses to assess the linearity of plasma and urine pharmacokinetics.

Results

Dose-normalized AUC and C_max were 37.1 ng ml⁻¹h [95% CI 35.5, 40.6] and 39.1 ng ml⁻¹ [95% CI 30.4, 50.2] for the microdose and 39.0 ng ml⁻¹h [95% CI 36.1, 42.1] and 37.1 ng ml⁻¹ [95% CI 26.9, 51.3] for the milligram dose. CL_met was 253 ml min⁻¹ [95% CI 201, 318] vs. 278 ml min⁻¹ [95% CI 248, 311] for intravenous doses and 1880 ml min⁻¹ [95% CI 1590, 2230] vs. 2050 ml min⁻¹ [95% CI 1720, 2450] for oral doses. Oral bioavailability of a midazolam microdose was 23.4% [95% CI 20.0, 27.3] vs. 20.9% [95% CI 17.1, 25.5] after the regular dose. Hepatic and gut extraction ratios for microgram doses were 0.44 [95% CI 0.39, 0.49] and 0.53 [95% CI 0.45, 0.63] and compared well with those for milligram doses (0.43 [95% CI 0.37, 0.49] and 0.61 [95% CI 0.53, 0.70]).

Conclusion

The pharmacokinetics of an intravenous midazolam microdose is linear to the applied regular doses and can be used to assess safely systemic CYP3A activity and, in combination with oral microdoses, pre-systemic CYP3A activity.     

柱前衍生，LC-MS/MS同时测定血浆中的孕二烯酮、依托孕烯和炔雌醇

建立LC-MS/MS同时测定血浆中孕二烯酮、依托孕烯和炔雌醇的方法。血浆样品经液-液萃取、柱前衍生处理后, 采用ESI离子源, 多反应离子监测 (MRM), 正离子扫描进行测定。以炔诺孕酮为内标, 采用C₁₈ (100 mm × 2.1 mm, 5 μm) 柱, 梯度流动相, 梯度流速测定血浆中孕二烯酮、依托孕烯和炔雌醇。结果表明, 孕二烯酮、依托孕烯分别在0.1～20 ng·mL⁻¹、炔雌醇在0.01～2 ng·mL⁻¹时线性关系良好, 精密度小于10.0%、方法回收率在93.6%～110.9%。对复方孕二烯酮和复方依托孕烯透皮给药制剂进行了家兔的药动学研究。本方法灵敏度高 (孕二烯酮、依托孕烯达到100 pg·mL⁻¹, 炔雌醇达到10 pg·mL⁻¹)、重现性好, 适合药动学研究。     

Determination of rat plasma levels of sertraline enantiomers using direct injection with achiral–chiral column switching by LC–ESI/MS/MS

A highly sensitive and selective on-line two-dimensional reversed-phase liquid chromatography/electrospray ionization–tandem mass spectrometric (2D-LC–ESI/MS/MS) method to determine sertraline (SRT) enantiomers in rat plasma was developed and validated. The method was applied to separate and determine the diastereomers and enantiomers of SRT simultaneously. The 2D-LC–ESI/MS/MS system consisted of RAM column in first dimension for trapping proteineous part of plasma and a chiral Cyclobond column as second dimension for separation of enantiomers and diastereomers of SRT using 0.1% aqueous trifluoroacetic acid:acetonitrile (86:14, v/v) as mobile phase in an isocratic elution mode. The linear dynamic range was 0.5–200 ng/mL (r² > 0.999). Acceptable precision and accuracy were obtained over the calibration range. The assay was successfully used in the analysis of SRT enantiomers in rat plasma to support pharmacokinetic studies.     

LC-MS/MS测定大鼠血浆中4-氯-2-氟-3-甲氧基苯硼酸及其毒代动力学研究

目的 建立一种快速灵敏的高效液相色谱串联质谱法（LC-MS/MS）用于大鼠血浆中PBA的测定,并进行PBA的毒代动力学研究。方法 观察SD大鼠分别灌胃及静脉注射染毒不同剂量PBA后血浆中PBA的浓度变化。采用内标法进行定量分析,获得血浆中PBA的浓度,并采用DAS药动学软件拟合主要动力学参数AUC、Cmax、Tmax、T1/2等。结果 血浆中PBA提取回收率为88.8%–94.4%,日间精密度为6.4%–8.9%,日内精密度为3.85%–5.87%,准确度为97.8%–105.5%。PBA的线性范围为20–2500 ng/ml,标准曲线的相关系数r>0.99。PBA的定量下限（LLOQ）为20 ng/mL ( RSD=9.67%,n=5)。结论 该方法能成功应用于PBA在大鼠体内的血浆毒代动力学。PBA在大鼠体内的暴露水平未随着染毒剂量的增加而线性增加,表明PBA在大鼠体内的吸收呈现饱和性。     

Quantitative determination of zidovudine diaryl phosphate triester pro-drugs in rat plasma by high-performance liquid chromatography–electrospray ionization tandem mass spectrometry

A rapid, simple, and sensitive high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI–MS/MS) method was developed and validated for quantitative analysis of 3′-azido-3′-deoxythymidine (zidovudine, AZT) diaryl phosphate triester pro-drugs, in rat plasma using 2′,3′-dideoxy-2′3′-didehydrothymidine (d4T) as internal standard (IS). The analytes were extracted from rat plasma with methanol after protein precipitation. The compounds were separated by HPLC with gradient elution (on a Shim-pack VP-ODS C₁₈ analytical column using a mobile phase of methanol/10 mM ammonium acetate). All the analytes were detected in positive ion mode using multiple reaction monitoring (MRM). The method was validated and the specificity, linearity, lower limit of quantitation (LLOQ), precision, accuracy, recoveries and stability were determined. LLOQs were 10 ng mL⁻¹ for M1, M2, M3, M4, and M5, respectively. Correlation coefficient (r) values for the linear range of 10–10,000 ng mL⁻¹ were greater than 0.999 for all the analytes. The intra-day and inter-day precision and accuracy were higher than 7.13%. The relative and absolute recovery was above 72% and no matrix effects were observed for all the analytes. This validated method provides a modern, rapid, and robust procedure for the pharmacokinetic studies of the pro-drugs after intravenous administration to rats. Some important results of AZT diaryl phosphate triester pro-drugs concerning chemical effect on pharmacokinetic performance are also studied.     

Characterization of metabolites of worenine in rat biological samples using liquid chromatography–tandem mass spectrometry

The in vivo and in vitro metabolites of worenine in rat were identified or characterized using a specific and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method. In vivo samples including rat urine, feces, and plasma samples were collected after ingestion of 25 mg/kg worenine to healthy rats. The in vivo and in vitro samples were cleaned up by a solid-phase extraction procedure (C18 cartridges) and a liquid–liquid extraction procedure, respectively. Then these pretreated samples were injected into a reversed-phase C18 column with mobile phase of methanol–ammonium acetate (2 mM, adjusted to pH 3.5 with formic acid) (60:40, v/v) and detected by an on-line MS/MS system. As a result, at least twenty-seven metabolites and the parent medicine were found in rat urine after ingestion of worenine. Seven metabolites and the parent medicine were identified or characterized in rat feces. Three metabolites and the parent medicine were detected in rat plasma. One metabolite was found in the rat intestinal flora incubation mixture, and three metabolites were characterized in the homogenized liver incubation mixture. The main phase I metabolism of worenine in rat was dehydrogenization, hydrogenation, hydroxylation, and demethylene reactions, and that of phase II was sulfation and glucuronidation.     

Determination of osthol and its metabolites in a phase I reaction system and the Caco-2 cell model by HPLC-UV and LC–MS/MS

A straightforward and sensitive reversed-phase high-performance liquid chromatography (HPLC) assay was developed and validated for the analysis of osthol and its phase I metabolites (internal standard: umbelliferone). The method was validated for the determination of osthol with respect to selectivity, precision, linearity, limit of detection, recovery, and stability. The linear response range was 0.47–60 μM, and the average recoveries ranged from 98 to 101%. The inter-day and intra-day relative standard deviations were both less than 5%. Using this method, we showed that more than 80% of osthol was metabolized in 20 min in a phase I metabolic reaction system. Transport experiments in the Caco-2 cell culture model indicated that osthol was easily absorbed with high absorptive permeability (>10 × 10⁻⁶ cm/s). The permeability did not display concentration-dependence or vectorial-dependence and is mildly temperature sensitive (activation energy less than 10 kcal/mol), indicating passive mechanism of transport. When analyzed by LC–MS/MS, five metabolites were detected in a phase I reaction system and in the receiver side of a modified Caco-2 cell model, which was supplemented with the phase I reaction system. The major metabolites appeared to be desmethyl-osthol and multiple isomers of dehydro-osthol. In conclusion, a likely cause of poor osthol bioavailability is rapid phase I metabolism via the cytochrome P450 pathways.     

Intracerebral microdialysis coupled to LC–MS/MS for the determination tramadol and its major pharmacologically active metabolite O‐desmethyltramadol in rat brain microdialysates

A rapid and sensitive method involving liquid chromatography electrospray tandem mass spectrometry (LC‐ESI‐MS/MS) coupled to an intracerebral microdialysis technique was developed for the determination and pharmacokinetic investigation of tramadol and its major active metabolite O ‐desmethyltramadol (ODT) in rat brain. The microdialysis samples were separated on a C18 column and eluted with a mobile phase of acetonitrile‐water‐formic acid (50:50:0.1; v/v/v ) at a flow rate of 0.3 mL/min. The ESI‐MS/MS spectra were performed in electrospray positive ion mode, and the analytes were detected by multiple reaction monitoring (MRM) of the transitions m/z [M + H]⁺ 264.3 → 58.2 for tramadol, m/z [M + H]⁺ 250.3 → 58.3 for ODT, and m/z [M + H]⁺ 379.4 → 264.0 for ambroxol (internal standard; IS). The total run time was 4.0 min. A lower limit of quantitation (LLOQ) was achieved as 1 ng/mL for tramadol and 0.5 ng/mL for ODT, with excellent linearity over a concentration range of 1 ~ 500 ng/mL (r  > 0.99) for tramadol and 0.5 ~ 50 ng/mL for ODT (r  > 0.99), respectively. The proposed method was successfully applied to the pharmacokinetic studies of tramadol and ODT in rat brain. Copyright © 2017 John Wiley & Sons, Ltd.     

Determination of lansoprazole in human plasma by rapid resolution liquid chromatography–electrospray tandem mass spectrometry: Application to a bioequivalence study on Chinese volunteers

A simple, sensitive and rapid LC/MS/MS method was developed for the quantification of lansoprazole in human plasma. After a simple sample preparation procedure by one-step protein precipitation with acetonitrile, lansoprazole and the internal standard bicalutamide were chromatographed on a Zorbax SB-C₁₈ (3.0 mm × 150 mm, 3.5 μm, Agilent) column with the mobile phase consisted of methanol–water (70:30, v/v, containing 5 mM ammonium formate, pH was adjusted to 7.85 by 1% ammonia solution). Detection was performed on a triple quadrupole tandem mass spectrometry by multiple reaction monitoring (MRM) mode via negative eletrospray ionization source (ESI⁻). The lower limit of quantification was 5.5 ng/mL, and the assay exhibited a linear range of 5.5–2200.0 ng/mL. The validated method was successfully applied to investigate the bioequivalence between two kinds of preparation (test vs. reference product) in twenty-eight healthy male Chinese volunteers.     

Determination of ranolazine in human plasma by LC-MS/MS and its application in bioequivalence study

A simple, sensitive and specific liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for quantification of ranolazine in human plasma. The analytical method consists in the precipitation of plasma sample with methanol, followed by the determination of ranolazine by an LC–MS/MS. The analyte was separated on a Peerless Cyano column (33 mm × 4.6 mm, 3 μm) an isocratic mobile phase of methanol–water containing formic acid (1.0%, v/v) (65:35, v/v) at a flow rate of 1.0 ml/min. Protonated ions formed by a turbo ionspray in positive mode were used to detect analyte and internal standard (IS). The MS/MS detection was made by monitoring the fragmentation of m/z 428.20 → 279.50 for ranolazine and m/z 448.30 → 285.20 for internal standard on a triple quadrupole mass spectrometer. The method was validated over the concentration range of 5–2000 ng/ml for ranolazine in human plasma with correlation coefficient of 0.9937 (S.D.: ±0.00367, range: 0.9895–0.9963). The accuracy and precision values obtained from six different sets of quality control samples analyzed in separate occasions ranged from 94.53 to 117.86 and 0.14% to 4.56%, respectively. Mean extraction recovery was 82.36–94.25% for three quality control (QC) samples and 88.37% for IS. Plasma samples were stable for three freeze–thaw cycles, or 24 h ambient storage, or 1 and 3 months storage at −20 °C. Processed samples (ready for injection) were stable up to 72 h at autosampler (4 °C). The developed method was successfully applied for analyzing ranolazine in plasma samples for a bioequivalence study with 12 healthy volunteers.     

Fabric phase sorptive extraction coupled with UPLC-ESI-MS/MS method for fast and sensitive quantitation of tadalafil in a bioequivalence study

The current study coupled fabric phase sorptive extraction (FPSE) with ultraperformance liquid chromatography method with electrospray ionization and tandem mass detection (UPLC-ESI-MS/MS) for fast and sensitive determination of tadalafil (TAD) in a bioequivalence study. Fabric phase sorptive extraction allowed direct extraction of TAD from the sample matrix with improved selectivity, repeatability, and recoveries. A sol–gel Carbowax 20 M (CX-20 M) coated FPSE membrane revealed the best extraction efficiency for TAD because of its strong affinity for analytes via intermolecular interactions, high mass transfer rate to FPSE membrane, and high permeability. An automated multiple reaction monitoring (MRM) optimizer was employed for the best selection of the precursor and product ions, ion breakdown profile, the fine adjustment of the fragmentor voltages for each precursor ions, and the collision energies for the product ions. The chromatographic separation was conducted using a mobile phase A: 5.0 mM ammonium acetate with 0.1 % formic acid in water and mobile phase B: formic acid (0.1%) in acetonitrile in ratio (55:45, v/v) through isocratic elution mode on an Agilent EclipsePlus C18 (50 × 2.1 mm, 1.8 μm) column and the flow rate was adjusted at 0.4 mL min^?1. The total run time per sample was 1.0 min. The method was validated by FDA standards for bioanalytical method validation over a concentration range of 0.1–100 ng mL^?1 with a correlation coefficient of 0.9993 and the lower limit of quantitation (LLOQ) was 0.1 ng mL^?1 in rat plasma. Intra- and inter-assay precision (%RSD) were lower than 4.1% and accuracy (%RE) was within 2.4%. The developed FPSE-UPLC-ESI-MS/MS method was effectively used in a randomized, two-way, single-dose, crossover study to compare the bioequivalence of two TAD formulations from different companies in male rats and verified to be bioequivalent.     

Interaction of talinolol and sulfasalazine in the human gastrointestinal tract

Summary The absorption of talinolol (TA) 50 mg was investigated without and together with the co-administration of sulfasalazine (SASP) 4 g in 11 healthy young volunteers, in order to clarify gastrointestinal transit of TA.Without SASP, the t_max of TA was 2.8 h, C_max was 112 ng·ml^–1 and the half life was 12 h; the AUC_o-t was 958 ng·ml^–1·h.In the case of concomitant administration of SASP, TA was found only in serum from 3 individuals, with a C_max of 23 ng·ml^–1 and a mean AUC_o-t of 84 ng·ml^–1·h. TA was not detectable in 5 subjects and it was at the limit of detection (2 ng·ml^–1) in 3 subjects. Pharmacokinetic analysis was not possible in any of those individuals.The reason for the interaction appears to be the adsorption of TA by SASP. An interval of 2–3 h should elapse between giving SASP and other drugs.     

Simple method for determination of hydrochlorothiazide in human urine by high performance liquid chromatography utilizing narrowbore chromatography

A simple high performance liquid chromatographic (HPLC) method utilizing narrowbore chromatography was developed for the determination of hydrochlorothiazide in human urine. A mobile phase of 0.1% aqueous acetic acid—acetonitrile (93:7, v/v) pH 3 was used with a C18 analytical column and ultraviolet detection (UV). The method demonstrated linearity from 2 to 50 μg ml⁻¹ using 50 μl of urine with a detection limit of 1 μg ml⁻¹. The method was utilized in a study evaluating if racial differences are present in the pharmacokinetic and pharmacodynamic effects of hydrochlorothiazide.     

Determination of dexmedetomidine in human plasma using high performance liquid chromatography coupled with tandem mass spectrometric detection: Application to a pharmacokinetic study

A rapid, sensitive and selective high performance liquid chromatography-electrospray ionization-tandem mass spectrometry method (HPLC-ESI-MS/MS) was developed and validated for the determination and pharmacokinetic investigation of dexmedetomidine (DMED) in human plasma. Dexmedetomidine and the internal standard (ondansetron) were extracted in a single step with diethyl-ether from 1.0 mL of alkalinized plasma. The mobile phase was a mixture of acetonitrile and 0.5% formic acid solution (30:70, v/v) at a flow rate of 0.2 mL min⁻¹. The detection was performed on a triple quadrupole tandem mass spectrometer in the selected reaction monitoring (SRM) mode using the respective [M+H]⁺ ions m/z 201.0 → 95.1 for DMED and m/z 294.1 → 170.1 for the IS. The assay exhibited a linear dynamic range of 5–5000 pg mL⁻¹ with the correlation coefficient above 0.9995. The lower limit of quantification (LLOQ) was 5 pg mL⁻¹ with a relative standard deviation of less than 15%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The validated HPLC-MS/MS method has been successfully applied to study the pharmacokinetics of three level doses of DMED in Chinese healthy volunteers.     

Ultraperformance liquid chromatography tandem mass spectrometric method for direct quantification of salbutamol in urine samples in doping control

A fast and reliable quantitative method for salbutamol using direct analysis of the urine sample by ultraperformance liquid chromatography tandem mass spectrometry (UPLC/MS/MS) has been developed. Urine samples were spiked with salbutamol-d₆ (internal standard), and, then, they were diluted with ultrapure water (1:1, v/v). Aliquots of 1 μl of the mixture were directly analyzed by UPLC/MS/MS. The chromatographic separation was performed in a UPLC BEH C₁₈ (100 mm × 2.1 mm, 1.7 μm) column with a mobile phase contained 0.01% formic acid in ultrapure water (v/v) and 0.01% formic acid in acetonitrile (v/v), using gradient elution at 0.6 ml/min. The temperature of the column was set to 45 °C. The total run time was 3.2 min. Electrospray ionization in positive ion mode was used under multiple reaction monitoring (MRM) at different collision energies. Nitrogen and argon were used as desolvation and collision gas, respectively. The method was shown to be linear from 200 to 5000 ng/ml (r² > 0.99). The limit of quantitation was estimated in 200 ng/ml. Intra-assay precision and accuracies, evaluated by using quality control samples containing 550 and 1100 ng/ml salbutamol, were always better than 8.4%. The intermediate precision was estimated to be in the range of 5.6–8.9%. The method was shown to be reliable when applying to routine samples, and the short analysis time resulting from a simple sample preparation and a fast instrumental analysis makes it of great interest for antidoping control purposes.     

Rapid UPLC–MS/MS method for the determination of ketoprofen in human dermal microdialysis samples

Dermal microdialysis (DMD) is a technique capable of determining the percutaneous penetration of drugs from topical formulations intended for local and/or regional activity. Typically, the concentrations of drug collected in dialysates are very low, generally in the ng/ml or even pg/ml range. An additional challenge is the very low volume of sample collected at each collection time and which can range from 1 to 30 μl only. Hence the objective was to develop and validate a rapid, accurate, precise, reproducible and highly sensitive LC–MS/MS method for the quantitative analysis of ketoprofen (KET) in dialystes following application of a topical gel product to the skin of human subjects. UPLC–MS/MS was used and KET was separated on an Acquity™ UPLC BEH C₁₈ column (100 mm × 2.1 mm i.d., 1.7 μm) and analysed in negative-ion (NI) electrospray ionisation (ESI) mode. The mobile phase (MP) consisted of acetonitrile:methanol:water (60:20:20, v/v/v) under isocratic conditions at a flow rate of 0.3 ml/min. Samples were extracted using ethyl acetate with ibuprofen (IBU) as internal standard (IS) and the organic solvent was then evaporated to dryness and the residue re-constituted in methanol. 5 μl samples were injected and analysis was performed at ambient temperature 22 ± 0.5 °C. KET and IBU eluted at 1.07 and 1.49 min, respectively. KET and IBU responses were optimised at the transitions 253.00 > 209.00 and 205.00 > 161.00, respectively. Calibration curves were linear over the range 0.5–500 ng/ml with correlation coefficients > 0.999. The accuracy and precision of the method were found to be between 99.97% and 104.67% (R.S.D. < 2%) and the mean recovery of KET from normal saline was 88.03 ± 0.3% (R.S.D. < 2.20%). The LLOQ and LOD values were found to be 0.5 and 0.1 ng/ml respectively whereas the ULOD was set at 500 ng/ml. The method was successfully applied to determine the bioavailability of KET following application of topical KET gel, Fastum^® gel, to the skin of human volunteers.