Ji Jiang

Safety, pharmacokinetics and pharmacodynamics of single doses of rivaroxaban – an oral, direct factor Xa inhibitor – in elderly Chinese subjects

Rivaroxaban is a novel, oral, direct factor Xa (FXa) inhibitor for the prevention and treatment of thromboembolic disorders. The aim of this study was to investigate the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of rivaroxaban in healthy, elderly Chinese subjects. In this single-centre, single-blind, placebo-controlled, parallel-group, dose-escalation study, 79 subjects, aged 59-74years (mean 62.8), were randomised to receive once-daily oral doses of rivaroxaban 5, 10, 20, 30 or 40mg. Rivaroxaban was well tolerated: there was a low incidence of treatment-emergent adverse events and all events were of mild intensity. Rivaroxaban was absorbed rapidly, reaching maximum plasma concentrations within 2-4hours. The PK of rivaroxaban were dose dependent over the dose range tested. Maximal inhibition of FXa occurred 2-3hours after dosing and returned to baseline after 24-48hours, reflecting rivaroxaban plasma concentrations. Inhibition of FXa was associated with dose-dependent effects on global clotting tests. There were no clinically relevant differences in rivaroxaban plasma concentrations between male and female subjects. In conclusion, rivaroxaban was well tolerated and was found to have predictable PK and PD in healthy, elderly Chinese subjects.

Important Role of the Dihydrouracil/Uracil Ratio in Marked Interpatient Variations of Fluoropyrimidine Pharmacokinetics and Pharmacodynamics

Dihydropyrimidine dehydrogenase (DPD) deficiency in patients causes severe toxicities in 5‐fluorouracil/floxuridine (5‐FU/FUDR) treatments. To determine the plasma dihydrouracil/uracil ratio (DUUR) as a potential index for setting 5‐FU/FUDR doses, the authors conducted a prospective study on the relationships of the DUUR with 5‐FU/FUDR pharmacokinetic and pharmacodynamic parameters. Forty gestational trophoblastic tumor (GTT) patients were treated with 30 mg/kg of 5‐FU or prodrug FUDR during a 10‐day cycle. The pretreatment DUURs of the patients were determined prior to the treatments, and plasma 5‐FU and FUDR concentrations on day 1 of the test cycle were measured to calculate the corresponding pharmacokinetic parameters. The absolute neutrophil count (ANC) and human chorionic gonadotrophins (HCG/β‐HCG) were recorded as the efficacy indexes. The correlation of the DUUR with pharmacokinetic parameters and efficacy indexes was analyzed to look for a relationship between individual doses (in milligrams) and the varied DUUR. Pretreatment DUUR was significantly correlated with the corresponding plasma AUC (r > 0.80, P < .01), the plasma drug clearance (r > 0.78, P < .01), the ANC (r > 0.76, P < 0.01), and the decrease of HCG/β‐HCG levels (r > 0.5, P < 0.01). In addition, the charts for setting 5‐FU/FUDR doses were designed for further validation in clinical trials. These findings indicate the important roles of the DUUR in remarkable interpatient variations of fluoropyrimidine pharmacokinetics and pharmacodynamics and propose a better index for setting individual 5‐FU/FUDR doses based on interpatient variations in DPD levels.

Measurement of endogenous uracil and dihydrouracil in plasma and urine of normal subjects by liquid chromatography-tandem mass spectrometry.

A sensitive and specific HPLC-MS-MS method was developed for the determination of endogenous uracil (Ura) and its metabolite dihydrouracil (UH2) in human plasma and urine samples. Plasma samples were extracted with ethyl acetate-isopropanol (85:15, v/v) following added ammonium sulfate, and then separated on a Discovery Amide C16 column with 3% methanol solution as the mobile phase; urine samples were just centrifuged at 2500 g for detection. Quantitation was carried out by LC-MS-MS in the multiple reaction monitoring (MRM) mode. The limits of quantitation of the method for Ura and UH2 were 0.5 and 5 ng ml(-1) (for plasma), and 50 and 100 ng ml(-1) (for urine), respectively. This method can be useful to evaluate the activity of dihydropyrimidine dehydrogenase (DPD), a rate-limiting enzyme of the chemotherapy drug fluoropyrimidine, which will be helpful in investigating subject variation of DPD and adjusting clinical dosage in pyrimidine chemotherapy.

Simultaneous quantitative determination of olmesartan and hydrochlorothiazide in human plasma and urine by liquid chromatography coupled to tandem mass spectrometry

A specific, sensitive and rapid method based on high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) was developed for the simultaneous determination of olmesartan (OLM) and hydrochlorothiazide (HCTZ) in human plasma and urine. Solid-phase extraction (SPE) was used to isolate the analytes from biological matrices followed by injection of the extracts onto a C(18) column with isocratic elution. Detection was carried out on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode using negative electrospray ionization (ESI). The method was validated over the concentration range of 1.00-1000 ng/mL and 5.00-5000 ng/mL for OLM in human plasma and urine as well as 0.500-200 ng/mL and 25.0-25,000 ng/mL for HCTZ in human plasma and urine, respectively. Inter- and intra-run precision of OLM and HCTZ were less than 15% and the accuracy was within 85-115% for both plasma and urine. The average extraction recoveries were 96.6% and 92.7% for OLM, and 87.2% and 72.1% for HCTZ in human plasma and urine, respectively. The linearity, recovery, matrix effect and stability were validated for OLM/HCTZ in human plasma and urine.

Determination of ginsenoside Rg3 in human plasma and urine by high performance liquid chromatography–tandem mass spectrometry

Here we report a method capable of quantifying ginsenoside Rg3 in human plasma and urine. The method was validated over linear range of 2.5-1000.0ngmL(-1) for plasma and 2.0-20.0ngmL(-1) for urine using ginsenoside Rg1 as I.S. Compounds were extracted with ethyl acetate and analyzed by HPLC/MS/MS (API-4000 system equipped with ESI(-) interface and a C(18) column). The inter- and intra-day precision and accuracy of QC samples were <or=8.5% relative error and were <or=14.4% relative standard deviation for plasma; were <or=5.6% and <or=13.3% for urine. The Rg3 was stable after 24h at room temperature, 3 freeze/thaw cycles and 131 days at -30 degrees C. This method has been applied to pharmacokinetic study of ginsenoside Rg3 in human.

Quantitative determination of icotinib in human plasma and urine using liquid chromatography coupled to tandem mass spectrometry

We developed a rapid, specific and sensitive method based on high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) to determine icotinib concentrations in human plasma and urine. Liquid-liquid extraction (LLE) and direct dilution were firstly used to isolate icotinib from plasma and urine followed by injection of the extracts onto a C(18) column with gradient elution. Ionization of icotinib and midazolam (internal standard, IS) was performed using an electrospray ionization source in positive mode and detection was carried out in multi-reaction monitoring (MRM) mode. The lower limits of quantitation (LLoQ) of icotinib in human plasma and urine by this method were 0.1 and 1.00ng/mL, respectively. The accuracy, precision, specificity, recovery, matrix effect, linearity and several of stabilities have been validated for icotinib in human plasma and urine. In conclusion, the validation results showed that this method is robust, specific and sensitive and it can successfully fulfill the requirement of clinical pharmacokinetic study of icotinib hydrochloride in Chinese healthy subjects.

Metabolite characterization of a novel anti‐cancer agent, icotinib, in humans through liquid chromatography/quadrupole time‐of‐flight tandem mass spectrometry

Icotinib is a novel anti-cancer drug that has shown promising clinical efficacy and safety in patients with non-small-cell lung cancer (NSCLC). At this time, the metabolic fate of icotinib in humans is unknown. In the present study, a liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (LC/Q-TOF MS) method was established to characterize metabolites of icotinib in human plasma, urine and feces. In addition, nuclear magnetic resonance (NMR) detection was utilized to determine the connection between side-chain and quinazoline groups for some complex metabolites. In total, 29 human metabolites (21 isomer metabolites) were characterized, of which 23 metabolites are novel compared to the metabolites in rats. This metabolic study revealed that icotinib was extensively metabolized at the 12-crown-4 ether moiety (ring-opening and further oxidation), carbon 15 (hydroxylation) and an acetylene moiety (oxidation) to yield 19 oxidized metabolites and to further form 10 conjugates with sulfate acid or glucuronic acid. To our knowledge, this is the first report of the human metabolic profile of icotinib. Study results indicated that significant attention should be paid to the metabolic profiles of NSCLC patients during the development of icotinib.

Single-dose and multiple-dose pharmacokinetics and safety of telbivudine after oral administration in healthy chinese subjects

The pharmacokinetics of telbivudine, an L‐nucleoside with potent activity against hepatitis B virus, was assessed in 42 healthy Chinese volunteers. Subjects were assigned to receive a single oral dose of 200, 400, or 800 mg telbivudine or repeat doses of 600 mg/d. Telbivudine was absorbed rapidly and exhibited dose‐related plasma exposure. After reaching maximum concentration (Cmax) at a median time of 2.0 to 2.5 hours, plasma disposition of the drug was biphasic with a mean terminal half‐life ranging from 39.4 to 49.1 hours. Telbivudine accumulated slightly after repeat doses, and steady state was reached after 5 to 6 consecutive doses of 600 mg/d. The mean steady‐state Cmax and area under the plasma concentration–time curve over the dosing interval of telbivudine 600 mg were 3.7 μg/mL and 26.1 μg·h/mL, respectively. Cumulative urinary excretion of telbivudine over 32 hours represented 24.4% of the administered dose, with a mean renal clearance of 6.6 L/h. Telbivudine was well tolerated in the studied dose range in healthy Chinese subjects, with no pattern of dose‐related clinical or laboratory adverse events.

A phase I study on pharmacokinetics and pharmacodynamics of higenamine in healthy Chinese subjects

Aim:To investigate the pharmacokinetics, pharmacodynamics, and safety of higenamine, an active ingredient of Aconite root, in healthy Chinese volunteers.Methods:Ten subjects received continuous, intravenous infusion of higenamine at gradually escalating doses from 0.5 to 4.0 μg·kg−1·min−1, each dose was given for 3 min. Blood and urine samples were collected at designated time points to measure the concentrations of higenamine. Pharmacodynamics was assessed by measuring the subjects heart rate. A nonlinear mixed-effect modeling approach, using the software Phoenix NLME, was used to model the plasma concentration-time profiles and heart rate.Results:Peak concentrations (Cmax) of higenamine ranged from 15.1 to 44.0 ng/mL. The half-life of higenamine was 0.133 h (range, 0.107–0.166 h), while the area under concentration-time curve (AUC), extrapolated to infinity, was 5.39 ng·h·mL−1 (range, 3.2-6.8 ng·h·mL−1). The volume of distribution (V) was 48 L (range, 30.8–80.6 L). The total clearance (CL) was 249 L/h (range, 199-336 L/h). Within 8 h, 9.3% (range, 4.6%–12.4%) of higenamine was recovered in the urine. The pharmacokinetics of higenamine was successfully described using a two-compartment model with nonlinear clearance. In the pharmacodynamic model, heart rates were related to the plasma drug concentrations using a simple direct effect model with baseline. The E0, Emax, and EC50 were 68 bpm, 73 bpm and 8.1 μg/L, respectively.Conclusion:Higenamine has desirable pharmacokinetic and pharmacodynamic characteristics. The results provide important information for future clinical studies on higenamine.

Determination of free and total vincristine in human plasma after intravenous administration of vincristine sulfate liposome injection using ultra-high performance liquid chromatography tandem mass spectrometry.

Vincristine sulfate liposome is a liposomal formulation of vincristine sulfate, a traditional anticancer drug, encapsulated in the aqueous core of phospholipid/cholesterol liposomes, which are kinds of targeted carriers to enhance malignancy targeting, exposure and anticancer activity of the drug. To evaluate and compare the pharmacokinetics of nonliposomal and liposome-encapsulated VCR and pharmacodynamic relationships associated with the toxicity and the efficacy behavior, it is essential to have a reliable method of separating the free and liposomal forms of the drug. In this paper, we have developed and validated methods to quantify the free vincristine (F-VCR) and total vincristine (T-VCR) in human plasma after intravenous administration of vincristine sulfate liposome injection (VSLI). The methods involve solid-phase extraction (SPE) for separating the F-VCR and liquid-liquid extraction (LLE) for releasing the VCR totally from the liposomal forms followed by an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method. The detection was performed on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode using positive electrospray ionization (ESI). The methods were validated over the concentration range of 0.2-50 ng/mL for F-VCR and 0.5-400 ng/mL for T-VCR, respectively. Inter- and intra-day precision (RSD%) were ≤4.7% for F-VCR and ≤9.8% for T-VCR, respectively. The accuracies were between -2.3 and 9.1% for F-VCR and between -3.2 and 6.9% for T-VCR, respectively. The extraction recovery and the matrix effect were investigated. The methods were successfully applied to the pharmacokinetic study of VSLI in Chinese subjects with lymphoma.