Mengqi Zhang

Determination of melamine and cyanuric acid in human urine by a liquid chromatography tandem mass spectrometry.

Melamine was found to be the etiological factor for the urinary stones epidemic in infants and young children in China in 2008. Urine level of melamine and its analog cyanuric acid may be useful markers for the evaluation of toxic effects. Liquid chromatography tandem mass spectrometry methods for the individual determination of melamine and cyanuric acid in human urine are described. Using isotope labeled internal standards during liquid-liquid extraction, the method was fully validated by verifying specificity, linearity, LLOQ, intra- and inter-assay precision and accuracy, matrix effect, recovery and stability. Calibration curves with good linearity (r=0.9999) over the concentration range from 10 to 5000 ng/ml, intra-assay precision <10% and inter-assay precision <15%, accuracy between 93.0 and 111.6% were obtained with multiple reaction monitoring mode for melamine and cyanuric acid in human urine. The methods were successfully applied to the analysis of urine samples collected from 86 infants and 110 adults.

Pharmacokinetics and Bioequivalence Evaluation of Two Different Atorvastatin Calcium 10-mg Tablets: A Single-Dose, Randomized-Sequence, Open-Label, Two-Period Crossover Study in Healthy Fasted Chinese Adult Males

BACKGROUND Atorvastatin calcium is a 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor indicated for the prevention of cardiovascular disease and for the treatment of dyslipidemia. Information on the pharmacokinetics of atorvastatin in a Chinese population is lacking, and regulatory requirements necessitate a bioequivalence study for the marketing of a generic product in China. OBJECTIVE The aim of the present study was to assess the pharmacokinetics and bioequivalence of a test and branded reference formulation of atorvastatin calcium 10-mg tablets in healthy fasted Chinese male volunteers. METHODS This was a single-dose, randomized-sequence, open-label, 2-period crossover study with a 2-week washout period between doses. Healthy Chinese males were randomly assigned to receive 20 mg of either the test or reference formulation, and 13 blood samples were obtained over a 48-hour interval. Plasma concentrations of parent atorvastatin and ortho-hydroxy-atorvastatin (primary active metabolite) were simultaneously determined using a validated liquid chromatography-isotopic dilution mass spectrometry method. Pharmacokinetic parameters, including C(max), T(max), t((1/2)), AUC(0-t), and AUC(0-infinity)), were calculated. The 2 formulations were to be considered bioequivalent if 90% CIs for the log transformed ratios of AUC and C(max) of atorvastatin were within the predetermined bioequivalence range (0.80-1.25 for AUC and 0.70-1.43 for C(max)) as established by the State Food and Drug Administration of China. Tolerability was evaluated throughout the study by vital signs monitoring, physical examinations, 12-lead ECGs, and subject interviews on adverse events (AEs). RESULTS A total of 66 subjects were assessed for inclusion; 20 were excluded prior to study initiation. Of the 46 healthy subjects (mean [SD] age, 24.1 [2.5] years; height, 170.8 [5.1] cm; weight, 64.6 [6.4] kg; body mass index (BMI), 22.1 [1.7] kg/m(2)) who completed the study, 45 subjects (mean [SD] age, 24.1 [2.5] years; height, 171.1 [4.9] cm; weight, 64.8 [6.3] kg; BMI, 22.1 [1.7] kg/m(2)) were included in the pharmacokinetic and bioequivalence analyses; 1 subject was excluded from these analyses because he mistakenly received the same formulation in both periods. No period or sequence effect was observed. The mean values of C(max), AUC(0-t), and AUC(0-infinity)) for the test and reference formulations of atorvastatin (8.78 and 10.76 ng/mL, 38.22 and 40.02 ng/mL/h, 42.73 and 44.51 ng/mL/h, respectively) and ortho-hydroxy-atorvastatin (5.78 and 5.77 ng/mL, 47.32 and 48.47 ng/mL/h, 52.36 and 53.14 ng/mL/h) were not significantly different. The 90% CIs for natural log-transformed ratios of C(max), AUC(0-t), and AUC(0-infinity)) of both atorvastatin (0.73-0.91, 0.92-1.02, and 0.91-1.01, respectively) and ortho-hydroxy-atorvastatin (0.83-1.05, 0.92-1.02, and 0.93-1.02) were within the bioequivalence acceptance limits. Three subjects (6.5%) reported a total of 4 mild AEs (1 abdominal discomfort and 3 venipuncture syncope), which were not considered to be associated with administration of the study drug. CONCLUSIONS This single-dose (20 mg) study found that the test and reference formulations of atorvastatin calcium 10-mg tablet met the regulatory definition for assuming bioequivalence in these healthy fasted Chinese male volunteers. Both formulations were generally well tolerated in the population studied. Chinese National Registry Code: 2007L02512.

Liquid chromatography tandem mass spectrometry method for determination of N-acetylcysteine in human plasma using an isotope-labeled internal standard

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to determine total N-acetylcysteine in human plasma. Mass spectrometric detection was achieved in positive electrospray ionization and multiple reaction monitoring mode. The mass transition pairs of N-acetylcysteine and the isotope-labeled internal standard d3-N-acetylcysteine were 164 → 122 and 167 → 123, respectively. The method was linear over the range of 10-5000 ng/mL in human plasma. The adoption of trichloroacetic acid significantly enhanced the extraction recovery. The blank matrix was screened to minimize the influence of endogenous N-acetylcysteine. After being fully validated, the method was successfully applied to the pharmacokinetic and bioequivalent study of N-acetylcysteine after oral administration of 600 mg tablets to 24 healthy Chinese volunteers.

Hair analysis, a reliable and non-invasive method to evaluate the contamination by clenbuterol.

The illegal use of clenbuterol has been an increasingly serious issue in todays livestock products industry. It becomes an important project to develop a reliable approach to detect its content in food animals. A simple and sensitive LC-MS/MS method was developed to detect clenbuterol residue in hair, with the low limit of quantitation (LLOQ) about 0.5ng/g. Hogs fed with 340µg/day of clenbuterol for 2 weeks were found a high clenbuterol residue in their hair approximately at 1-2 months after withdrawal. There remained 3.31ng/g clenbuterol in hog hair approximately 5 months after the last administration, focused on the tip of the hair (mainly in hogs with dark hair). An extensive contamination was observed in twenty investigated market hogs whose dark hair obviously had a higher clenbuterol residue than the light ones (p=0.017, t test). Volunteers (60.3 percent) from Xuhui district (Shanghai) were found to have a detectable amount of clenbuterol in their hair (>0.5ng/g). In conclusion, hair residue detection is a reliable method to evaluate the clenbuterol contamination in animals and humans. Meat supply in the Xuhui district might have serious potential safety risks which should be further investigated and discussed to determine the safety range of clenbuterol residue.

Pharmacokinetics and bioequivalence evaluation of two losartan potassium 50-mg tablets: a single-dose, randomized-sequence, open-label, two-way crossover study in healthy Chinese male volunteers

BACKGROUND Losartan is a nonpeptide angiotensin II receptor antagonist used as an antihypertensive agent. The relative bioavailability of a newly developed tablet compared with an established branded formulation has not been reported in a Chinese population. OBJECTIVE To meet the requirements for marketing a new generic product, the study was designed to compare the pharmacokinetic parameters and relative bioavailability of a new generic losartan potassium 50-mg tablet (test formulation) with a branded 50-mg tablet (reference formulation) in healthy Chinese male volunteers. METHODS A single-dose, randomized-sequence, openlabel, 2-way crossover study was conducted in healthy Chinese male volunteers. Eligible participants were randomly assigned in a 1:1 ratio to receive a single 50-mg tablet of the test or reference formulation, followed by a 1-week washout period and then administration of the alternate formulation. The study drugs were administered after a 10-hour overnight fast. Plasma samples were collected over 36 hours. Tolerability was evaluated by recording adverse events (AEs) and monitoring vital signs, ECGs, and laboratory tests at baseline and at completion of the study. Plasma concentrations of losartan and its active metabolite (EXP3174) were analyzed by LC-MS/MS. Pharmacokinetic parameters, including C(max), AUC(0-36), and AUC(0-infinity), were calculated. If the 90% CIs for the log-transformed values of AUC were within 80% to 125%, and that of C(max) was within 70% to 143%, the 2 products would be considered bioequivalent according to the guidelines of the US Food and Drug Administration and the State Food and Drug Administration of China. RESULTS Twenty-seven healthy Chinese male volunteers participated in this study (mean [SD] age, 24.5 [2.3] years [range, 20-29 years]; weight, 64.6 [4.0] kg [range, 60.0-75.0 kg]; height, 172.2 [4.8] cm [range, 165.0183.0 cm]; and body mass index, 21.8 [1.2] kg/m(2) [range, 20.0-25.0 kg/m(2)]). One volunteer (3.7%) experienced an AE (microscopic hematuria) after administration of the test formulation. This resolved spontaneously after 10 days and was considered by the investigator as mild; the relationship with the study drug was uncertain. No serious AEs were reported. Both formulations were associated with significant reductions in systolic and diastolic blood pressure and significant increases in heart rate compared with baseline values (all, P < 0.05). No period, formulation, or sequence effects were observed for any pharmacokinetic parameter, except for a significant subject effect. For parent losartan, the 90% CIs for the ratios (test/reference) of C(max), AUC(0-36), and AUCAUC(0-infinity) were 83.65% to 113.36%, 89.79% to 98.25%, and 90.95% to 99.55%, respectively. For the metabolite EXP3174, the 90% CIs for the ratios of C(max), AUC(0-36), and AUCAUC(0-infinity) were 93.49% to 103.61%, 96.79% to 104.09%, and 97.06% to 105.83%. Both C(max) and AUC met the predetermined criteria for assuming bioequivalence. The relative bioavailability of the test formulation to the reference formulation was 93.92% for losartan and 100.40% for EXP3174. CONCLUSIONS In this small study in healthy Chinese male volunteers, a single 50-mg oral dose of a losartan potassium tablet (test formulation) met the regulatory criteria for assuming bioequivalence to the established reference formulation. Both formulations were well tolerated.

Pharmacokinetic and bioequivalence comparison between orally disintegrating and conventional tablet formulations of flurbiprofen: A single-dose, randomized-sequence, open-label, two-period crossover study in healthy chinese male volunteers

BACKGROUND Flurbiprofen, an NSAID, is used for the treatment of inflammation and pain caused by rheumatoid arthritis and osteoarthritis as well as soft-tissue injuries. A new orally disintegrating tablet (ODT) of flurbiprofen has recently been developed; this study was conducted to provide support for this drug to obtain marketing authorization in China. OBJECTIVE The aim of the study was to compare the pharmacokinetic properties and bioequivalence of flurbiprofen 50-mg ODT (test) with a conventional flurbiprofen 50-mg tablet (reference) under fasting conditions in healthy volunteers. METHODS This was a single-dose, randomized-sequence, open-label, 2-period crossover study. Healthy, nonsmoking Chinese male volunteers were randomly assigned to receive 150 mg (administered as three 50-mg tablets) of either the test or reference formulation of flurbiprofen, followed by a 7-day washout period and administration of the alternate formulation. Study drugs were administered after a 12-hour overnight fast. Blood samples were collected before dosing and at 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 hours after dosing. Serum flurbiprofen concentrations were analyzed using a validated nonstereospecific liquid chromatography/tandem mass spectrometry method. Pharmacokinetic parameters, including C(max), T(max), t(1/2), AUC(0-24), and AUC(0-infinity), were calculated and analyzed statistically. C(max), AUC(0-24), and AUC(0-infinity) were used to test for bioequivalence after natural logarithm (ln)-transformation. Tolerability was evaluated throughout the study by clinical assessments, vital sign monitoring, physical examinations, 12-lead ECG, clinical laboratory tests, and questioning subjects about adverse events (AEs). RESULTS A total of 20 Chinese males (mean [SD] age, 21.4 [2.5] years [range, 19-28 years]; height, 174.4 [4.2] cm [range, 169-183 cm]; weight, 63.2 [5.1] kg [range, 56-78 kg]; body mass index, 20.8 [1.4] kg/m(2) [range, 19-24 kg/m(2)]) completed the study. No period or sequence effect was observed. The 90% CIs for the ln-transformed ratios of Cmax, AUC(0-24), and AUC(0-infinity) were 99.9% to 115.9%, 97.8% to 107.9%, and 100.3% to 110.9%, respectively, meeting the predetermined criteria for bioequivalence. Two subjects (10.0%) experienced 1 of 2 mild AEs (increase in total bilirubin and dizziness), which were not considered to be associated with study drug administration. CONCLUSIONS This single-dose 150-mg (three 50-mg tablets) study of each formulation of flurbiprofen found that the test and reference products met the regulatory criteria for bioequivalence in these fasting healthy Chinese male volunteers. Both formulations were generally well tolerated. State Food and Drug Administration of China study registration number: 2005L04356.

Development and validation of an HPLC-MS/MS method to determine clopidogrel in human plasma.

A quantitative method for clopidogrel using online-SPE tandem LC–MS/MS was developed and fully validated according to the well-established FDA guidelines. The method achieves adequate sensitivity for pharmacokinetic studies, with lower limit of quantifications (LLOQs) as low as 10 pg/mL. Chromatographic separations were performed on reversed phase columns Kromasil Eternity-2.5-C18-UHPLC for both methods. Positive electrospray ionization in multiple reaction monitoring (MRM) mode was employed for signal detection and a deuterated analogue (clopidogrel-d4) was used as internal standard (IS). Adjustments in sample preparation, including introduction of an online-SPE system proved to be the most effective method to solve the analyte back-conversion in clinical samples. Pooled clinical samples (two levels) were prepared and successfully used as real-sample quality control (QC) in the validation of back-conversion testing under different conditions. The result showed that the real samples were stable in room temperature for 24 h. Linearity, precision, extraction recovery, matrix effect on spiked QC samples and stability tests on both spiked QCs and real sample QCs stored in different conditions met the acceptance criteria. This online-SPE method was successfully applied to a bioequivalence study of 75 mg single dose clopidogrel tablets in 48 healthy male subjects.

Bioequivalence and pharmacokinetic evaluation of two formulations of glimepiride 2 mg: A single-dose, randomized-sequence, open-label, two-way crossover study in healthy chinese male volunteers

BACKGROUND Glimepiride is an oral sulfonylurea antihyperglycemic agent indicated for the treatment of type 2 diabetes mellitus. Although there are reports in the literature regarding the pharmacokinetic (PK) characteristics of glimepiride, few data of PK parameters are available in a Chinese population; none are available regarding a recently developed generic formulation. OBJECTIVE To meet the requirements for marketing a new generic product in China, the study was designed to compare the PK properties and bioequivalence of 2-mg tablets of glimepiride: the newly developed generic formulation (test) and a branded formulation (reference) in healthy Chinese male volunteers. METHODS A single-dose, randomized-sequence, open-label, 2-way crossover study was conducted in fasted healthy Chinese male volunteers. Eligible participants were randomly assigned in a 1:1 ratio to receive 1 tablet (2 mg each) of the test or reference formulation, followed by a 1-week washout period and administration of the alternate formulation. The study drugs were administered after a 10-hour overnight fast. Plasma samples were collected before study drug administration (baseline) and at 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 10, 12, 24, and 48 hours after study drug administration. Concentrations in plasma of the parent glimepiride and its M1 metabolite were analyzed with a LC-MS/MS method. The formulations were considered bioequivalent if the 90% CIs for the log-transformed values were within the predetermined equivalence range (70%-143% for C(max) and 80%-125% for AUC), according to the guidelines of the State Food and Drug Administration (SFDA) of China. Tolerability was based on the recording of adverse events (AEs), monitoring vital signs, ECGs, and laboratory tests at baseline and completion of the study. RESULTS A total of 24 healthy Chinese male volunteers were enrolled and completed the study; however, only the data from 23 subjects were included (mean [SD] age, 23.6 [2.2] years [range, 18.6-26.9 years]; weight, 64.0 [8.4] kg [range, 52.0-82.0 kg]; and height, 172.3 [5.6] cm [range, 164.0-185.0 cm) in the PK and tolerability assessments due to a violation of the protocol. For parent glimepiride, the 90% CIs for the ratios of Cmax, AUC(0-t), and AUC(0-infinity) were 93.83% to 115.19%, 90.82% to 102.29%, and 92.22% to 103.78%, respectively. For the M1 metabolite, the 90% CIs were 91.71% to 110.79%, 91.33% to 101.76%, and 89.99% to 99.85%. Both met the predetermined criteria for bioequivalence. Four AEs (17.4%) were reported: hypertriglyceridemia (2 subjects [8.7%]; 1 each receiving the test and reference formulations); increase of red blood cells in urine (1 subject [4.3%] receiving the reference formulation); and hypoglycemia (1 subject [4.3%] receiving the test formulation). The incidence of hypoglycemia was the only AE considered probably related to study drug administration; all others were considered probably not related. All AEs were transient and considered by the investigators to be mild. CONCLUSIONS In this small study in fasted healthy Chinese male volunteers, a single 2-mg dose of the test formulation met the regulatory criteria to assume bioequivalence to the reference formulation based on the rate and extent of absorption. Both formulations were well tolerated. SFDA Registration No.: 2009L01033.

Simultaneous determination of itraconazole and hydroxyitraconazole in human plasma by liquid chromatography-isotope dilution tandem mass spectrometry method.

A rapid and sensitive liquid chromatography-isotope dilution tandem mass spectrometry method was developed and validated for quantification of itraconazole (ITZ) and its active metabolite hydroxyitraconazole (OH-ITZ ) in human plasma. The plasma samples were extracted with tert-butyl methyl ether and two isotope-labeled internal standards (D5-itraconazole and D5-hydroxyitraconazole) were used. The chromatographic separation was performed on a Capcell Pak C(18) MG III (100 x 2 mm, 5 microm, Shiseido). The protonated ions of analytes were detected in positive ionization in multiple reaction monitoring mode. The plasma method has a lower limit of quantification of 1 ng/mL with a linearity range of 1-500 ng/mL for ITZ and OH-ITZ using 100 microL of plasma. The recoveries of the method were found to be 69.47-71.98% for ITZ and 75.68-82.52% for OH-ITZ. The intra- and inter-batch precision was less than 11% for all quality control samples at concentrations of 2.5, 200 and 400 ng/mL. These results indicate that the method was efficient with a short run time (4.5 min) and acceptable accuracy, precision and sensitivity.The validated method was successfully applied to analysis of human plasma samples in pharmacokinetics study.

Liquid chromatography tandem mass spectrometry method for determination of bisoprolol in human plasma using d5-bisoprolol as the internal standard.

A simple, reliable and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) protocol was developed and validated for quantification of bisoprolol in human plasma. The sample was pretreated with a simple procedure of protein precipitation and an isotope-labeled d5-bisoprolol was used as internal standard. The chromatographic separation was performed on a Capcell Pak C(18) MG III column (100 mm x 2.0 mm, 5 microm). The protonated ion of the analyte was detected in positive ionization by multiple reaction monitoring mode. The mass transition pairs of m/z 326.3 --> 116.3 and m/z 331.3 --> 121.3 were used to detect bisoprolol and the internal standard, respectively. Linearity, accuracy, precision, recovery, matrix effect, dilution test and stability were evaluated during method validation over the range of 0.5-100 ng/mL. The validated method was successfully applied to analyze human plasma samples in a bisoprolol bioavailability study.