Yiling Huang

Development and validation of a liquid chromatography–tandem mass spectrometric assay for pitavastatin and its lactone in human plasma and urine

A rapid, selective and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method with electrospray ionization (ESI) was developed and validated for the simultaneous determination of pitavastatin and its lactone in human plasma and urine. Following a liquid-liquid extraction, both the analytes and internal standard racemic i-prolact were separated on a BDS Hypersil C(8) column, using methanol-0.2% acetic acid in water (70: 30, v/v) as the mobile phase. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode using the transition m/z 422.4-->m/z 290.3 for pitavastatin, m/z 404.3-->m/z 290.3 for pitavastatin lactone and m/z 406.3-->m/z 318.3 for the internal standard, respectively. Linear calibration curves of pitavastatin and its lactone were obtained in the concentration range of 1-200 ng/ml, with a lower limit of quantitation of 1 ng/ml. The intra- and inter-day precision values were less than 4.2%, and accuracies were between -8.1 and 3.5% for both analytes. The proposed method was utilized to support clinical pharmacokinetic studies of pitavastatin in healthy subjects following oral administration.

Effect of Organic Anion-Transporting Polypeptide 1B1 (OATP1B1) Polymorphism on the Single- and Multiple-Dose Pharmacokinetics of Enalapril in Healthy Chinese Adult Men

BACKGROUND Enalapril is an angiotensin-converting enzyme (ACE) inhibitor approved for the treatment of mild to severe hypertension and congestive heart failure. There is evidence that enalapril may be an organic anion-transporting polypeptide 1B1 (OATP1B1) substrate, suggesting that genetic polymorphisms of the OATP1B1 gene may play a role in causing the interindividual pharmacokinetic differences of this drug. OBJECTIVE The purpose of this study was to investigate the functional significance of the OATP1B1 genetic polymorphism on the pharmacokinetics of enalapril and its active metabolite enalaprilat in healthy Chinese adult male participants. METHODS This was a single-center, open-label, single- and multiple-dose study conducted in healthy Chinese male participants. Each participant received a single oral dose of 10 mg enalapril under fasting conditions, followed by enalapril 10 mg/d for 7 days. In the single-dose phase, sequential blood samples were collected from 0 to 24 hours after drug administration. In the multiple-dose phase, samples were obtained before drug administration on days 4, 5, 6, and 7; on day 7, samples were collected from 0 to 72 hours after drug administration. An HPLC-MS/MS method was used to determine plasma concentrations of enalapril and enalaprilat. A polymerase chain reaction technique was used for genotyping of 2 single nucleotide polymorphisms (SNPs) of the OATP1B1 gene: T521C and A388G. The pharmacokinetic parameters of enalapril and enalaprilat were then compared according to genotype groups, using 1-way ANOVA, except for T(max) in which the Mann-Whitney test or Kruskal-Wallis test was used. RESULTS The study included 32 healthy Han Chinese male participants (age range, 18-28 years; weight range, 50.0-80.0 kg; height range,159-182.0 cm). Twenty-six were OATP1B1*15 noncarriers (homozygous for 521TT), the others were *15 carriers with at least one 521 T>C mutant allele. After single and multiple oral doses of 10 mg enalapril, plasma concentrations of enalapril in *15 noncarriers were lower than that in *15 carriers, with significant difference in area under the curve at steady state (AUC(ss)) between *15 noncarriers and *15 carriers (P = 0.048) in the multiple-dose phase. There were no significant differences in enalaprils AUC(0-24), C(max), or the ratio of the AUC(0-24h) in the single-dose study to the AUC(ss) (R(ac)) between the *15 carriers and noncarriers. In contrast to enalapril, the mean AUC(0-24h) and C(max) of enalaprilat in *15 noncarriers was significantly higher than those in *15 carriers (P = 0.040 and P = 0.027, respectively) in the single-dose phase. There were no significant differences in enalaprilats AUC(ss) or C(maxss) between the 2 groups in the multiple-dose phase. For the 3 groups classified according to the effect of A388G variant in all subjects homozygous for 521T (TT), *1a/*1a, *1a/*1b, and *1b/*1b, no significant difference was found in AUC(0-24h), C(max), and T(max) of enalapril and enalaprilat. CONCLUSIONS In this small population of healthy Chinese men, the OATP1B1*15 allele and T521C variant appeared to be an important determinant of the pharmacokinetics of enalapril. There were significant differences between the *15 carriers and noncarriers in enalaprils AUC(ss) and enalaprilats AUC(0-24h), C(max), and R(ac). However, there were no significant differences in enalaprils AUC(0-24), C(max), or enalaprilats AUC(ss), C(maxss) between the *15 carriers and noncarriers.

Enantioselective and sensitive determination of carvedilol in human plasma using chiral stationary-phase column and reverse-phase liquid chromatography with tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometry method to quantify carvedilol enantiomers in human plasma was developed and validated as a measure of compliance in clinical research. Carvedilol enantiomers were extracted from human serum (0.5 mL) via liquid-liquid extraction with methyl tert-butyl ether (2.5 mL). Carvedilol-related compound C served as the internal standard. The analyte and internal standard were separated on a Sino-Chiral AD column (150 × 4.6mm, 5 μm, amylose tris-3,5-dimethylphenylcarbamate coated on silica-gel) using isocratic elution with mobile phases of methanol, water and diethylamine (94:6:0.01, v/v). The total run-time was 10.5 min. Carvedilol enantiomers were quantified using a triple quadrupole mass spectrometer operated in multiple-reaction-monitoring mode using positive electrospray ionisation. The mass transitions monitored for quantitation were carvedilol (m/z 407→222) and carvedilol-related compound C (m/z 497→222). The limits of quantification for the S- and R-carvedilol enantiomers in plasma were both 0.08 ng/mL. The method was validated in the linear range of 0.08-50 ng/mL with acceptable inter- and intra-assay precision and accuracy and stability suitable for routine laboratory practice. The method was successfully applied to samples taken from research volunteers treated with carvedilol sustained-release tablet 18 mg. Cmax and AUClast were 9.1 ± 5.1 ng/mL and 59.4 ± 39.6 ng h/mL for R-carvedilol, 4.0 ± 2.3 ng/mL and 24.7 ±15.0 ng h/mL for S-carvedilol, respectively. tmax and t1/2 were 4.6 ± 1.9h and 9.6 ± 4.5h for R-carvedilol, and 4.7 ± 1.0 h and 10.7 ± 5.7 h, respectively.

Development and validation of a sensitive LC-MS/MS-ESI method for the determination of ivabradine in human plasma: application to a pharmacokinetic study.

A sensitive, rapid assay method for estimating ivabradine in human plasma has been developed and validated using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive-ion mode. The procedure involved extraction of ivabradine and the internal standard (IS) from human plasma by solid-phase extraction. Chromatographic separation was achieved using an isocratic mobile phase (0.1% formic acid-methanol, 60:40, v/v) at a flow rate of 1.0 mL/min on an Aglient Eclipse XDB C8 column (150 × 4.6 mm, 5 µm; maintained at 35 °C) with a total run time of 4.5 min. Detection was achieved using an Applied Biosystems MDS Sciex (Concord, Ontario, Canada) API 3200 triple-quadrupole mass spectrometer. The MS/MS ion transitions monitored were 469-177 for ivabradine and 453-177 for IS. Method validation was performed according to Food and Drug Administration guidelines, and the results met the acceptance criteria. The calibration curve was linear over a concentration range of 0.1-200 ng/mL. The lower limit of quantitation achieved was 0.1 ng/mL. Intra- and inter-day precisions were in the range of 1.23-14.17% and 5.26-8.96%, respectively. Finally, the method was successfully used in a pharmacokinetic study that measured ivabradine levels in healthy volunteers after a single 5 mg oral dose of ivabradine. Copyright

Plasma α1-antitrypsin: A Neglected Predictor of Angiographic Severity in Patients with Stable Angina Pectoris

Background:As an acute phase protein, &agr;1-antitrypsin (AAT) has been extensively studied in acute coronary syndrome, but it is unclear whether a relationship exists between AAT and stable angina pectoris (SAP). The purpose of the present study was to investigate the association between AAT plasma levels and SAP. Methods:Overall, 103 SAP patients diagnosed by coronary angiography and clinical manifestations and 118 control subjects matched for age and gender were enrolled in this case-control study. Plasma levels of AAT, high-sensitivity C-reactive protein (hsCRP), lipid profiles and other clinical parameters were assayed for all participants. The severity of coronary lesions was evaluated based on the Gensini score (GS) assessed by coronary angiography. Results:Positively correlated with the GS (r = 0.564, P < 0.001), the plasma AAT level in the SAP group was significantly higher than that in the control group (142.08 ± 19.61 mg/dl vs. 125.50 ± 19.67 mg/dl, P < 0.001). The plasma AAT level was an independent predictor for both SAP (odds ratio [OR] = 1.037, 95% confidence interval [CI]: 1.020–1.054, P < 0.001) and a high GS (OR = 1.087, 95% CI: 1.051–1.124, P < 0.001) in a multivariate logistic regression model. In the receiver operating characteristic curve analysis, plasma AAT level was found to have a larger area under the curve (AUC) for predicting a high GS (AUC = 0.858, 95% CI: 0.788–0.929, P < 0.001) than that of hsCRP (AUC = 0.665, 95% CI: 0.557–0.773, P = 0.006; Z = 2.9363, P < 0.001), with an optimal cut-off value of 137.85 mg/dl (sensitivity: 94.3%, specificity: 68.2%). Conclusions:Plasma AAT levels correlate with both the presence and severity of coronary stenosis in patients with SAP, suggesting that it could be a potential predictive marker of severe stenosis in SAP patients.

Pharmacokinetic and pharmacodynamic characteristics of aranidipine sustained-release, enteric-coated tablets in healthy Chinese men: a phase I, randomized, open-label, single- and multiple-dose study.

OBJECTIVE The aim of this study was to explore the pharmacokinetic (PK) and pharmacodynamic (PD) properties and safety profiles of aranidipine and its active M-1 metabolite in healthy Chinese men. METHODS This Phase I, randomized, open-label, single- and multiple-dose study included healthy, nons-moking male volunteers aged 18 to 45 years. In the single-dose study, subjects were randomly assigned to receive oral sustained-release, enteric-coated aranidipine tablets 5, 10, or 20 mg. In the multiple-dose study, volunteers who had been assigned to the aranidipine 10-mg group in the single-dose study received this dose for 7 days. In the single-dose study, blood samples for the PK analyses were obtained immediately before dosing and at regular intervals up to 36 hours after dosing. In the multiple-dose study, predose blood samples were collected on days 4 through 7; on the last day of treatment, blood samples were drawn at the same times as in the single-dose study. Plasma concentrations of aranidipine and M-1 were determined using a high-performance liquid chromatography method with tandem mass-spectrometric detection. For the PD analyses, blood pressure (BP) and heart rate were measured before dosing, at regular intervals up to 24 hours after dosing, and after the final dose during repeated administration. Tolerability was assessed throughout the study, based on adverse events, physical examinations, electrocardiography, vital signs, and laboratory tests. RESULTS The study enrolled 30 healthy Chinese men (mean [SD] age, 23 [2] years; mean body weight, 66 [7] kg; mean height, 174 [6] cm). In the single-dose study, the mean t(1/2) for aranidipine 5, 10, and 20 mg was 3.0 (2.7), 2.7 (1.1), and 3.1 (2.2) hours, respectively; mean T(max) was 4.9 (0.4), 4.4 (1.0), and 4.3 (0.9) hours; mean C(max) was 1.1 (0.6), 2.4 (0.8), and 4.0 (2.0) microg/L; and mean AUC(last) was 4.1 (1.4), 10.3 (2.3), and 20.9 (4.2) microg . h/L. There were no significant differences in any PK parameter between dose groups. For M-1, the corresponding values were 4.6 (1.0), 4.1 (0.5), and 4.1 (0.3) hours for t(1/2); 5.6 (2.0), 5.0 (1.6), and 5.0 (0.8) hours for T(max); 18.4 (0.6), 40.5 (10.0), and 39.2 (11.3) microg/L for C(max); and 143.5 (39.1), 304.5 (108.2), and 403.9 (73.5) microg . h/L for AUC(last). Only dose-normalized Cmax and AUC(last) differed significantly between dose groups (P < 0.001 and P = 0.018, respectively). After multiple doses, the mean values for t(1/2), T(max), C(max), and AUC(0-infinity) for aranidipine 10 mg were 2.3 (0.9) hours, 5.0 (1.2) hours, 3.1 (1.1) microg/L, and 13.8 (3.6) microg . h/L, respectively. Repeated oral administration of aranidipine 10 mg was associated with a significant increase in AUC(last) (P = 0.027). The corresponding values for M-1 were 4.8 (0.9) hours, 5.7 (1.3) hours, 40.0 (11.3) microg/L, and 381.8 (161.2) microg . h/L. There were no significant differences between dose groups in any PK parameter for M-1 after single or multiple doses. In the PD analyses, the mean change from baseline in diastolic BP was statistically significant in all groups (P < 0.01) except the aranidipine 10-mg group in the single-dose study. Three volunteers (10%) reported adverse events after administration of a single dose: headache (10-mg group), palpitations (20-mg group), and dizziness (20-mg group). The headache and palpitations were considered possibly related to study drug. CONCLUSIONS The results of this small study in healthy Chinese men suggest that the PK properties of aranidipine were linear with respect to dose, whereas the PK properties of the active M-1 metabolite were not fully linear. There was no apparent accumulation of aranidipine or M-1 with administration of single and multiple doses. Aranidipine was generally well tolerated.

A rapid and sensitive LC–MS/MS-ESI method for the determination of tolvaptan and its two main metabolites in human plasma

A liquid chromatography-tandem mass spectrometry (LC-MS) method to quantify tolvaptan and its two main metabolites and applied to human study was first developed and validated as a measure of compliance in clinical research. Because of the structure similarity of tolvaptan and its multiple metabolites, the method was optimized to obtain a chromatographic and MS separation of the endogenous interference and isotope ions as well as high analysis throughput. Tolvaptan, its two main metabolites and the internal standard were extracted from human serum (0.1mL) using solid-phase extraction, separated on a Waters nova-pak C18 column (150×3.9mm, 5μm) using isocratic elution with a mobile phase composed of acetonitrile, water and formic acid (65:35:0.25, v/v/v). The total run-time was shortened to 3.5min. The mass transition ranges under positive electrospray ionisation that were monitored for quantitation included m/z 449-252 for tolvaptan, m/z 479-252 for metabolite DM-4103, m/z 481-252 for metabolite DM-4107 and m/z 463-266 for the internal standard (IS). The limit of quantification in plasma for all three analytes was 1ng/mL. The method was validated over a linear range from 1 to 500ng/mL for all three analytes with acceptable inter- and intra-assay precision and accuracy. The stability of the analytes was determined to be suitable for routine laboratory practices. The method was successfully applied to samples taken from research volunteers who ingested a 15mg tolvaptan tablet.

Population Pharmacokinetic/Pharmacodynamics Modeling of Ibutilide in Chinese Healthy Volunteers and Patients With Atrial Fibrillation (AF) and/or Atrial Flutter (AFL)

PURPOSE The goal of this study was to develop a population pharmacokinetic (PK) and PK/pharmacodynamics (PD) model for ibutilide, to evaluate the time course of its effect on QT interval in Chinese. METHODS The population PK and PK/PD model were developed using data from 40 Chinese healthy volunteers using nonlinear mixed-effects modeling, and the final population PK/PD model was applied on 100 patients with atrial fibrillation (AF) and/or atrial flutter (AFL). FINDINGS The PK parameters of ibutilide were best described by a 3-compartment model with first-order elimination. No statistically significant covariate was found for each PK model parameter. Individualized QT interval correction, by heart rate, was performed by a power model, and the circadian rhythm of QT intervals was described by 2 mixed-effect cosine functions. The QT interval data of ibutilide was well characterized by a sigmoid Emax model (E(C)=Emaxγ×Cγ/(EC50γ+Cγ)) with an effect compartment. The final PK/PD model was used to estimate individual parameters of patient data and found good predictions compared with healthy volunteers; AF and/or AFL patients had lower Emax and higher EC50. IMPLICATIONS A population PK and PK/PD model for ibutilide in healthy volunteers was developed and could well capture ibutilides PK/PD characteristics. The final PK/PD model was applied on patients with AF and/or AFL successfully.